S

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S-100 bus n. A 100-pin bus specification used in the design of computers built around the Intel 8080 and Zilog Z-80 microprocessors. System designs using the Motorola 6800, 68000, and Intel iAPx86 family of microprocessors have also been built around the S-100 bus. S-100 computers were extremely popular with early computer enthusiasts. They had an open architecture, which permitted the configuration of systems with a wide range of add-on expansion boards.

SA n. Identifier for Intel s line of RISC-based microprocessors for portable and embedded devices. See also StrongARM.

SAA n. Acronym for Systems Application Architecture. An IBM-developed standard for the appearance and operation of application software that will give programs written for all IBM computers mainframe computers, minicomputers, and personal computers a similar look and feel. SAA defines how an application interfaces with both the user and the supporting operating system. True SAA-compliant applications are compatible at the source level (before being compiled) with any SAA-compliant operating system provided the system is capable of furnishing all the services required by the application.

Sad Mac n. An error indication that occurs on Apple Macintosh computers when the system fails the initial diagnostic test. A Sad Mac is a picture of a Macintosh with a frowning face and X s for eyes, with an error code beneath the picture.

safe mode n. In some versions of Windows, such as Windows 95, a boot mode that bypasses startup files and loads only the most basic drivers. Safe mode allows the user to correct some problem with the system for example, if the system fails to boot or the registry has become corrupted. See also boot¹.

salt n. Random data used to supplement encryption schemes. A salt value allows two identical packets of data to be encrypted into two different packets of ciphertext using the same key by changing the salt value with each packet. Also called: salt string, salt value.

Samba n. A popular freeware program that provides file and print services, authentication and authorization, name resolution, and service announcement (browsing). As a file server, Samba enables the sharing of files, printers, and other resources on a UNIX Samba server with Windows clients over a network. Based on the Server Message Block (SMB) protocol, Samba originally was developed as a Network File System (NFS) for UNIX by Andrew Tridgell. See also NFS, SMB.

sampling vb. 1. In statistics, gathering data from a representative subset of a larger group (called a population) for example, determining a country s presumed voting pattern by polling a demographic cross section of voters. Other uses of this type of sampling might include checking the accuracy and efficiency of computerized transactions by reviewing every hundredth transaction or predicting traffic volumes by measuring traffic flow in a few strategic streets. There are many statistical procedures for estimating how accurately a given sample reflects the behavior of a group as a whole. 2. The conversion of analog signals to a digital format; samples are taken at periodic intervals to measure and record some parameter, such as a signal from a temperature sensor or a microphone. Analog-to-digital converters are used in computers to sample analog signals as voltages and convert them to the binary form a computer can process. The two primary characteristics of this type of sampling are the sampling rate (usually expressed in samples per second) and the sampling precision (expressed in bits; 8-bit samples, for instance, can measure an input voltage accurate to 1/256 of the measured range).

sampling rate n. The frequency with which samples of a physical variable, such as sound, are taken. The higher the sampling rate (that is, the more samples taken per unit of time), the more closely the digitized result resembles the original. See also sampling (definition 2).

sampling synthesizer n. A device designed to reproduce sounds, at differing frequencies, based on a digitized sound stored in read-only memory. For example, a recorded piano note, digitized and stored in memory, is used by the synthesizer to create other piano-like notes.

samurai n. A hacker employed by a company or organization to manage network security or conduct legal cracking operations. A samurai uses the skills of a hacker to meet the legitimate needs of an employer.

SAN n. See storage area network.

sandbox n. 1. Java Virtual Machine security area for downloaded (remote or untrusted) applets, an area in which such applets are confined and prevented from accessing system resources. Confinement to the sandbox prevents downloaded applets from carrying out potentially dangerous operations, maliciously or otherwise. They have to play inside the sandbox, and any attempt to escape is thwarted by the Java Security Manager. 2. Slang for the research and development department at many software and computer companies. See also applet, Java Virtual Machine.

sans serif adj. Literally, without stroke ; describes any typeface in which the characters have no serifs (the short lines or ornaments at the upper and lower ends of the strokes). A sans serif typeface usually possesses a more straightforward, geometric appearance than a typeface with serifs and typically lacks the contrast between thick and thin strokes found in serif faces. Sans serif typefaces are used more frequently in display type, such as headlines, than in blocks of text. Compare serif¹.

SAOL n. Acronym for Structured Audio Orchestra Language. Part of the MPEG-4 standard, SAOL describes a set of tools for producing computer music, audio for computer games, streaming Internet sound or music, and other multimedia applications. SAOL is a flexible computer language for describing music synthesis and integrating synthetic sound with recorded sound in an MPEG-4 bit stream. See also bit stream, MPEG-4, streaming (definition 1).

SAP n. See Service Advertising Protocol.

SAPI n. Acronym for Speech Application Programming Interface. A feature in Windows 9x and Windows NT that allows applications to include speech recognition or convert text to speech. Also called: Speech API. See also voice recognition.

SAS n. See single attachment station.

SASL n. Acronym for Simple Authentication and Security Layer. An authentication support mechanism for use with connection-based protocols. SASL allows a client to request identification from a server and negotiate use of an added security layer for authentication during subsequent client/server interaction.

satellite n. See communications satellite.

satellite computer n. A computer that is connected to another computer, with which it interacts over a communications link. As its name indicates, a satellite computer is of lesser stature than the main, or host, computer; the host controls either the satellite itself or the tasks the satellite performs. See also remote communications.

satellite dish n. A parabolic (dish-shaped) reflector and antenna that is used for transmitting and receiving signals between the ground and earth satellites. Satellite dishes are commonly used for receiving television transmissions.

saturated mode n. The state in which a switching device or amplifier is passing the maximum possible current. A device is in saturated mode when increasing the control signal does not result in output of additional current.

saturation n. 1. In a switching device or amplifier, the fully conducting state. At saturation, the device is passing the maximum possible current. The term is most commonly used with reference to circuits containing bipolar or field-effect transistors. 2. In color graphics and printing, the amount of color in a specified hue, often specified as a percentage. See also HSB.

save vb. To write data (typically a file) to a storage medium, such as a disk or tape.

SAX n. Acronym for Simple API for XML. An event-driven application program interface (API) used to interpret an XML file. SAX works with an XML parser, providing an interface between the parser and an XML application. SAX is used as an alternative to the more complex object-based Document Object Model (DOM) interface. See also DOM.

scalability n. A measure of how well a computer, service, or application can grow to meet increasing performance demands. For server clusters, it is the ability to incrementally add one or more systems to an existing cluster when the overall load of the cluster exceeds its capabilities. See also server cluster.

scalable adj. Of or relating to the characteristic of a piece of hardware or software or a network that makes it possible for it to expand or shrink to meet future needs and circumstances. For example, a scalable network allows the network administrator to add many additional nodes without the need to redesign the basic system.

scalable font n. Any font that can be scaled to produce characters in varying sizes. Examples of scalable fonts are screen fonts in a graphical user interface, stroke fonts (such as Courier) and outline fonts common to most PostScript printers, TrueType fonts, and the method for screen font definition used in Macintosh System 7. In contrast, most text-based interfaces and printing devices (such as daisy-wheel printers) offer text in only one size. See also outline font, PostScript font, screen font, stroke font, TrueType.

scalable parallel processing n. Multiprocessing architectures in which additional processors and additional users can easily be added without excessive increases in complexity and loss of performance. Acronym: SPP.

Scalable Processor Architecture n. See SPARC.

Scalable Vector Graphics n. See SVG.

scalar n. A factor, coefficient, or variable consisting of a single value (as opposed to a record, an array, or some other complex data structure). Compare vector.

scalar data type n. A data type defined as having a predictable and enumerable sequence of values that can be compared for greater-than/less-than relationships. Scalar data types include integers, characters, user-defined enumerated data types, and (in most implementations) Boolean values. Some debate exists as to whether or not floating-point numbers can be considered a scalar data type; although they can be ordered, enumeration is often questionable because of rounding and conversion errors. See also Boolean expression, enumerated data type, floating-point number.

scalar processor n. A processor designed for high-speed computation of scalar values. A scalar value can be represented by a single number.

scalar variable n. See scalar.

scale¹ n. A horizontal or vertical line on a graph that shows minimum, maximum, and interval values for the data plotted.

scale² vb. 1. To enlarge or reduce a graphic display, such as a drawing or a proportional character font, by adjusting its size proportionally. 2. To alter the way in which values are represented so as to bring them into a different range for example, to change linear feet to quarter inches on a blueprint drawing of a house. 3. In programming, to determine the number of digits occupied by fixed-point or floating-point numbers. See also fixed-point notation, floating-point number.

scaling n. In computer graphics, the process of enlarging or reducing a graphical image scaling a font to a desired size or scaling a model created with a CAD program, for example. See also CAD.

scan vb. 1. In television and computer display technologies, to move an electron beam across the inner surface of the screen, one line at a time, to light the phosphors that create a displayed image. 2. In facsimile and other optical technologies, to move a light-sensitive device across an image-bearing surface such as a page of text, converting the light and dark areas on the surface to binary digits that can be interpreted by a computer.

scan code n. A code number transmitted to an IBM or compatible computer whenever a key is pressed or released. Each key on the keyboard has a unique scan code. This code is not the same as the ASCII code for the letter, number, or symbol shown on the key; it is a special identifier for the key itself and is always the same for a particular key. When a key is pressed, the scan code is transmitted to the computer, where a portion of the ROM BIOS (read-only memory basic input/output system) dedicated to the keyboard translates the scan code into its ASCII equivalent. Because a single key can generate more than one character (lowercase a and uppercase A, for example), the ROM BIOS also keeps track of the status of keys that change the keyboard state, such as the Shift key, and takes them into account when translating a scan code. Compare key code.

scan head n. An optical device found in scanners and fax machines that moves across the subject being scanned, converts light and dark areas to electrical signals, and sends those signals to the scanning system for processing.

scan line n. 1. One of many horizontal lines of a graphics display screen, such as a television or raster-scan monitor. 2. A single row of pixels read by a scanning device.

scanner n. An optical input device that uses light-sensing equipment to capture an image on paper or some other subject. The image is translated into a digital signal that can then be manipulated by optical character recognition (OCR) software or graphics software. Scanners come in a number of types, including flatbed (scan head passes over a stationary subject), feed (subject is pulled across a stationary scan head), drum (subject is rotated around a stationary scan head), and handheld (user passes device over a stationary subject).

scan rate n. See refresh rate.

scatter diagram n. A graph consisting of points whose coordinates represent values of data, often used to illustrate a correlation between one or more variables and a test group. See the illustration. Also called: point chart, point diagram.

Scatter diagram.

schedule vb. To program a computer to perform a specified action at a specified time and date.

scheduler n. An operating-system process that starts and ends tasks (programs), manages concurrently running processes, and allocates system resources. Also called: dispatcher.

scheduling algorithm n. An algorithm that governs the proper timing of a sequence of events in an operating system or application. For example, an effective motion graphics scheduling algorithm would be able to retrieve the graphic objects, process them, and display them without causing stutter or disruptions. See also algorithm.

schema n. A description of a database to a database management system (DBMS) in the language provided by the DBMS. A schema defines aspects of the database, such as attributes (fields) and domains and parameters of the attributes.

schematic n. A diagram that shows a circuit s components and the connections between them using lines and a set of standard symbols to represent various electronic components. See the illustration.

Schematic.

Schottky diode n. A type of diode (device that passes current in one direction) in which a semiconductor layer and a metal layer are brought into contact. It is characterized by very fast switching speeds. Also called: hot carrier diode, Schottky barrier diode.

scientific notation n. A floating-point method of representing a number, especially a very large or very small one, in which numbers are expressed as products consisting of a number between 1 and 10 multiplied by a power of 10. Scientific notation commonly uses the letter E in place of times 10, as in 5.0E3, meaning 5.0 times 10 to the third power, or 10³. See also floating-point notation.

sci. newsgroups n. Usenet newsgroups that are part of the sci. hierarchy and begin with sci. These newsgroups are devoted to discussions of scientific research and applications, except for computer science, which is discussed in the comp. newsgroups. See also newsgroup, traditional newsgroup hierarchy, Usenet. Compare comp. newsgroups, misc. newsgroups, news. newsgroups, rec. newsgroups, soc. newsgroups, talk. newsgroups.

scissoring n. See clip.

scope n. 1. In programming, the extent to which an identifier, such as a constant, data type, variable, or routine, can be referenced within a program. Scope can be global or local. Scope can also be affected by redefining identifiers, such as by giving the same name to both a global variable and a local variable. See also block(definition 3), global, local. 2. In electronics, slang for oscilloscope. See also oscilloscope.

score n. When referring to a spelling checker, a score is a number that indicates how much a replacement word differs from the original misspelled word. A low score indicates that the misspelled word was changed slightly, while a high score indicates that the word was changed a great deal.

SCP n. Acronym for Simple Control Protocol. A lightweight peer-to-peer networking protocol for devices that have limited processing and memory resources and operate over limited-bandwidth networks such as powerline carrier (PLC) systems. Products using SCP can interoperate with products using the Universal Plug and Play (UPnP), CEBus, and Home Plug & Play (HPnP) standards. Developed by a team of companies including Microsoft and General Electric, SCP enables the interaction between UPnP devices, devices based on Internet Protocol (IP), and non-IP-capable devices such as coffeemakers and alarm clocks. SCP, which was designed as a stand-alone protocol, can be used in residential, commercial, industrial, and utility applications. See also UPnP networking.

SCR n. See silicon-controlled rectifier.

scrambler n. A device or program that reorders a signal sequence in order to render it indecipherable. See also encryption.

scrap n. An application or system file maintained for storing data that has been marked for movement, copying, or deletion. See also clipboard (definition 1).

scrapbook n. 1. A file in which a series of text and graphical images can be saved for subsequent use. 2. A Macintosh system file that can hold a number of text and graphical images for later use. Compare clipboard (definition 1).

scratch¹ n. A memory region or file used by a program or operating system to hold work in progress temporarily. Created and maintained usually without the end user s knowledge, the scratch is needed only until the current session is terminated, at which time the data is saved or discarded. Also called: scratch file. See also temporary file. Compare scrap.

scratch² vb. To erase or discard data.

scratch file n. See scratch¹.

scratchpad n. 1. A temporary storage area used by a program or operating system for calculations, data, and other work in progress. See also scratch¹, temporary file. 2. A high-speed memory circuit used to hold small items of data for rapid retrieval. See also cache.

scratchpad memory n. See cache.

scratchpad RAM n. Memory used by a central processing unit (CPU) for temporary data storage. Also called: scratchpad, scratchpad memory. See also central processing unit, register.

scream vb. To operate at very high speed. For example, a modem that can transfer data several times faster than the one it replaced or a computer with a very high clock speed could be said to scream.

screamer n. Slang for a piece of computer equipment that operates at a very high speed. Generally, screamers are the newest versions of a particular piece of equipment, such as a PC with the latest, fastest microprocessor, or are comprised of multiple components that increase the operating speed over standard models, such as a PC that has a huge amount of RAM (Random Access Memory), a high-performance video board, a superfast CD-ROM drive, and the latest microprocessor. However, as technology evolves and new, faster devices are introduced, yesterday s screamer rapidly becomes today s snail.

screen angle n. The angle at which the dots in a halftone screen are printed. A correct angle will minimize blur and other undesirable effects, such as moir patterns. See also color separation (definition 1), halftone, moir .

screen buffer n. See video buffer.

screen dump n. A duplicate of a screen image; essentially, a snapshot of the screen that is either sent to a printer or saved as a file.

screen flicker n. See flicker.

screen font n. A typeface designed for display on a computer monitor screen. Screen fonts often have accompanying PostScript fonts for printing to PostScript-compatible printers. See also derived font, intrinsic font. Compare PostScript font, printer font.

screen frequency n. See halftone.

screen grabber n. See grabber (definition 3).

screen name n. A name under which an America Online user is known. The screen name may be the same as the user s real name. See also America Online.

screen phone n. A type of Internet appliance combining a telephone with an LCD display screen, a digital fax modem, and a computer keyboard, with ports for a mouse, printer, and other peripheral devices. Screen phones can be used as regular telephones for voice communications and can also be used as terminals to gain access to the Internet and other online services.

screen pitch n. A measurement of a computer monitor s screen density, representing the distance between phosphors on the display. The lower the number, the more detail can be displayed clearly. For example, a .28-dot-pitch screen has better resolution than one with .32. See the illustration. See also phosphor.

Screen pitch.

screen saver n. A utility that causes a monitor to blank out or display a certain image after a specified amount of time passes without the keyboard being touched or the mouse being moved. Touching a key or moving the mouse deactivates the screen saver. Screen savers were originally used to prevent images from becoming permanently etched on a monitor s screen. Although modern monitors are not susceptible to this problem, screen savers remain popular for their decorative and entertainment value. See the illustration.

Screen saver.

screen shot n. An image that shows all or part of a computer display.

ScreenTips n. Notes that appear on the screen to provide information about a toolbar button, tracked change, or comment or to display a footnote or an endnote. ScreenTips also display the text that will appear if you choose to insert a date or AutoText entry.

script n. A program consisting of a set of instructions to an application or a utility program. The instructions usually use the rules and syntax of the application or utility. On the World Wide Web, scripts are commonly used to customize or add interactivity to Web pages. See also macro.

scripting language n. A simple programming language designed to perform special or limited tasks, sometimes associated with a particular application or function. An example of a scripting language is Perl. See also Perl, script.

script kiddie n. A would-be hacker who does not have the technical skills or knowledge needed for traditional hacking methods; one who relies on easy-to-use kiddie scripts. See also hacker, kiddie script.

scriptlet n. A reusable Web page based on the features of Dynamic HTML (DHTML) that can be created with HTML text and a scripting language and then inserted as a control in another Web page or in an application. Developed by Microsoft and introduced in Internet Explorer version 4, scriptlets are implemented as .htm files that give developers a relatively easy, object-based means of creating components that reflect the Web metaphor and that can be used to add interactivity and functionality for example, animation, color changes, pop-up menus, or drag-and-drop capability to Web pages without requiring repeated trips to the server. Also called: Microsoft Scripting Component. See also dynamic HTML. Compare applet.

scroll vb. To move a document or other data in a window in order to view a particular portion of the document. Scrolling may be controlled by the mouse, arrow keys, or other keys on the keyboard. See also scroll bar.

scroll arrow n. See scroll bar.

scroll bar n. In some graphical user interfaces, a vertical or horizontal bar at the side or bottom of a display area that can be used with a mouse for moving around in that area. Scroll bars often have four active areas: two scroll arrows for moving line by line, a sliding scroll box for moving to an arbitrary location in the display area, and gray areas for moving in increments of one window at a time.

scroll box n. See elevator.

Scroll Lock key n. On the IBM PC/XT and AT and compatible keyboards, a key on the top row of the numeric keypad that controls the effect of the cursor control keys and sometimes prevents the screen from scrolling. On the enhanced and Macintosh keyboards, this key is to the right of the function keys on the top row. Many modern applications ignore the Scroll Lock setting.

scroll wheel n. A thumbwheel on a mouse that, when turned, enables the user to scroll or zoom without clicking the scroll bar or using the keyboard. Depending on the mouse, a scroll wheel can also double as a third mouse button. See also scroll bar.

SCSI n. Acronym for Small Computer System Interface, a standard high-speed parallel interface defined by the X3T9.2 committee of the American National Standards Institute (ANSI). A SCSI (pronounced scuzzy ) interface is used to connect microcomputers to SCSI peripheral devices, such as many hard disks and printers, and to other computers and local area networks. Also called: SCSI-1, SCSI I. Compare ESDI, IDE.

SCSI-1 n. See SCSI.

SCSI-2 n. An enhanced ANSI standard for SCSI (Small Computer System Interface) buses. Compared with the original SCSI standard (now called SCSI-1), which can transfer data 8 bits at a time at up to 5 MB per second, SCSI-2 offers increased data width, increased speed, or both. A SCSI-2 disk drive or host adapter can work with SCSI-1 equipment at the older equipment s maximum speed. Also called: SCSI II. See also Fast SCSI, Fast/Wide SCSI, SCSI, Wide SCSI. Compare UltraSCSI.

SCSI bus n. A parallel bus that carries data and control signals from SCSI devices to a SCSI controller. See also bus, controller, SCSI device.

SCSI chain n. A set of devices on a SCSI bus. Each device (except the host adapter and the last device) is connected to two other devices by two cables, forming a daisy chain. See also daisy chain, SCSI.

SCSI connector n. A cable connector used to connect a SCSI device to a SCSI bus. See the illustration. See also bus, connector (definition 1), SCSI device.

SCSI connector.

SCSI device n. A peripheral device that uses the SCSI standard to exchange data and control signals with a computer s CPU. See also peripheral, SCSI.

SCSI I n. See SCSI.

SCSI II n. See SCSI-2.

SCSI ID n. The unique identity of a SCSI device. Each device connected to a SCSI bus must have a different SCSI ID. A maximum of eight SCSI IDs can be used on the same SCSI bus. See also bus, SCSI device.

SCSI network n. A set of devices on a SCSI bus, which acts like a local area network. See also SCSI.

SCSI port n. 1. A SCSI host adapter within a computer, which provides a logical connection between the computer and all of the devices on the SCSI bus. See also SCSI. 2. A connector on a device for a SCSI bus cable. See also SCSI.

SDH n. See Synchronous Digital Hierarchy.

SDK n. Acronym for software development kit. See developer s toolkit.

SDLC n. Acronym for Synchronous Data Link Control, the data transmission protocol most widely used by networks conforming to IBM s Systems Network Architecture (SNA). SDLC is similar to the HDLC (High-level Data Link Control) protocol developed by the International Organization for Standardization (ISO). See also HDLC.

SDM n. See space-division multiplexing.

SDMI n. See Secure Digital Music Initiative.

SDRAM n. Acronym for synchronous DRAM. A form of dynamic random access memory (DRAM) that can run at higher clock speeds than conventional DRAM by employing a bursting technique in which the DRAM predicts the address of the next memory location to be accessed. See also dynamic RAM.

SDSL n. Acronym for symmetric (or single-line) digital subscriber line, a digital telecommunications technology that is a variation of HDSL. SDSL uses one pair of copper wires rather than two pairs of wires and transmits at 1.544 Mbps. Compare ADSL.

.sea n. A file extension for a self-extracting Macintosh archive compressed with StuffIt. See also self-extracting file.

seamless integration n. The favorable result that occurs when a new hardware component or program blends smoothly into the overall operation of the system. It is usually the result of thoughtful design and programming.

search¹ n. The process of seeking a particular file or specific data. A search is carried out by a program through comparison or calculation to determine whether a match to some pattern exists or whether some other criteria have been met. See also binary search, hash search, linear search, search and replace, wildcard character.

search² vb. 1. To look for the location of a file. 2. To seek specific data within a file or data structure. See also replace.

search algorithm n. An algorithm designed to locate a certain element, called the target, in a data structure. See also algorithm, binary search, hash search, linear search.

search and replace n. A common process in applications such as word processors in which the user specifies two strings of characters. The process finds instances of the first string and replaces them with the second string.

search criteria n. The terms or conditions that a search engine uses to find items in a database. See also search engine.

search engine n. 1. A program that searches for keywords in documents or in a database. 2. On the Internet, a program that searches for keywords in files and documents found on the World Wide Web, newsgroups, Gopher menus, and FTP archives. Some search engines are used for a single Internet site, such as a dedicated search engine for a Web site. Others search across many sites, using such agents as spiders to gather lists of available files and documents and store these lists in databases that users can search by keyword. Examples of the latter type of search engine are Lycos and Excite. Most search engines reside on a server. See also agent (definition 2), FTP, Gopher or gopher, newsgroup, spider, World Wide Web.

search key n. 1. The particular field (or column) of the records to be searched in a database. See also primary key, secondary key. 2. The value that is to be searched for in a document or any collection of data.

search path n. The route followed by an operating system to find the location of a stored file. The search path begins with a drive or volume (disk) designator or a network share, continues through a chain of directories and subdirectories, if any, and ends with the file name. C:\books\diction\start.exe is an example of a search path. Also called: access path.

search string n. The string of characters to be matched in a search typically (but not necessarily) a text string.

seat¹ n. One workstation or computer, in the context of software licensing on a per-seat basis. See also license agreement, workstation (definition 1).

seat² vb. To insert a piece of hardware fully and position it correctly in a computer or affiliated equipment, as in seating a single inline memory module (SIMM) in its socket.

secondary channel n. A transmission channel in a communications system that carries testing and diagnostic information rather than actual data. Compare primary channel.

secondary key n. A field that is to be sorted or searched within a subset of the records having identical primary key values. See also alternate key (definition 1), candidate key. Compare primary key.

secondary service provider n. An Internet service provider that provides a Web presence but not direct connectivity. See also ISP.

secondary storage n. Any data storage medium other than a computer s random access memory (RAM) typically tape or disk. Compare primary storage.

Second Generation n. See 2G.

second-level domain n. The level immediately beneath the top-level domain in the Internet s DNS hierarchy. See also domain (definition 3).

second normal form n. See normal form (definition 1).

secret channel n. See private channel.

section n. A length of fiberoptic cable in a SONET network. See also line, path.

sector n. A portion of the data storage area on a disk. A disk is divided into sides (top and bottom), tracks (rings on each surface), and sectors (sections of each ring). Sectors are the smallest physical storage units on a disk and are of fixed size; typically, they are capable of holding 512 bytes of information apiece. See the illustration.

Sector.

sector interleave n. See interleave.

sector map n. 1. A map that indicates the unusable sectors on a disk. 2. A table used to translate the sector numbers that are requested by the operating system into physical sector numbers. The sector map represents a different method of performing sector interleaving. When a sector map is used, the sectors are formatted on the disk in sequential order. The mapping enables the system to read sectors in a nonsequential order. For example, using a 3-to-1 sector interleaving map, a system request for sectors 1 through 4 will result in the disk driver reading physical sectors 1, 4, 7, and 10. See also interleave.

secure channel n. A communications link that has been protected against unauthorized access, operation, or use by means of isolation from the public network, encryption, or other forms of control. See also encryption.

Secure Digital Music Initiative n. A coalition of companies from the recording, electronics, and information technology industries founded in February 1999 for the purpose of developing an open standard for the secure distribution of music in digital form. The Secure Digital Music Initiative specification is designed to provide consumers with flexibility and convenient access to electronically distributed music (that is, over the Internet) while also protecting the rights of artists. Acronym: SDMI. See also MP3, Windows Media Technologies.

Secure Electronics Transactions protocol n. Protocol for conducting secure transactions over the Internet, the result of a joint effort by GTE, IBM, MasterCard, Microsoft, Netscape, SAIC, Terisa Systems, VeriSign, and Visa. Acronym: SET.

Secure Hash Algorithm n. See SHA.

Secure HTTP n. See S-HTTP, HTTPS.

Secure Hypertext Transfer Protocol n. See S-HTTP.

Secure/Multipurpose Internet Mail Extensions n. See S/MIME.

Secure Password Authentication n. A feature that allows a server to confirm the identity of the person logging on. Acronym: SPA.

secure site n. A Web site having the capability of providing secure transactions, ensuring that credit card numbers and other personal information will not be accessible to unauthorized parties.

Secure Sockets Layer n. See SSL.

Secure Transaction Technology n. The use of the SSL (Secure Sockets Layer), S-HTTP (Secure HTTP), or both in online transactions, such as form transmission or credit card purchases. Acronym: STT. See also S-HTTP, SSL.

secure wide area network n. A set of computers that communicate over a public network, such as the Internet, but use security measures, such as encryption, authentication, and authorization, to prevent their communications from being intercepted and understood by unauthorized users. Acronym: S/WAN. See also authentication, authorization, encryption, virtual private network (definition 1).

security n. The technologies used to make a service resistant to unauthorized access to the data that it holds or for which it is responsible. A major focus of computer security, especially on systems that are accessed by many people or through communications lines, is the prevention of system access by unauthorized individuals.

security kernel n. An operating-system kernel that is protected from unauthorized use. See also kernel.

security log n. A log, generated by a firewall or other security device, that lists events that could affect security, such as access attempts or commands, and the names of the users involved. See also firewall, log (definition 1).

seed n. A starting value used in generating a sequence of random or pseudorandom numbers. See also random number generation.

seek n. The process of moving the read/write head in a disk drive to the proper site, typically for a read or write operation.

seek time n. The time required to move a disk drive s read/write head to a specific location on a disk. See also access time (definition 2).

segment n. A section of a program that, when compiled, occupies a contiguous address space and that is usually position independent; that is, it can be loaded anywhere in memory. With Intel-based microcomputers, a native-mode segment is a logical reference to a 64-KB contiguous portion of RAM in which the individual bytes are accessed by means of an offset value. Collectively, the segment:offset values reference a single physical location in RAM. See also overlay¹ (definition 1), real mode, segmentation.

segmentation n. The act of breaking up a program into several sections, or segments. See also segment.

segmented addressing architecture n. A memory-access technique typified by Intel 80x86 processors. Memory is divided into 64-KB segments in this architecture for addressing locations under the 16-bit address scheme; 32-bit schemes can address memory in segments as large as 4 GB. Also called: segmented instruction addressing, segmented memory architecture. Compare linear addressing architecture.

segmented address space n. An address space that is logically divided into chunks called segments. To address a given location, a program must specify both a segment and an offset within that segment. (The offset is a value that references a specific point within the segment, based on the beginning of the segment.) Because segments may overlap, addresses are not unique; there are many logical ways to access a given physical location. The Intel 80x86 real-mode architecture is segmented; most other microprocessor architectures are flat. See also segment. Compare flat address space.

segmented instruction addressing n. See segmented addressing architecture.

segmented memory architecture n. See segmented addressing architecture.

select vb. 1. In general computer use, to specify a block of data or text on screen by highlighting it or otherwise marking it with the intent of performing some operation on it. 2. In database management, to choose records according to a specified set of criteria. See also sort. 3. In information processing, to choose from a number of options or alternatives, such as subroutines or input/output channels.

selected cell n. See active cell.

selection n. 1. In applications, the highlighted portion of an on-screen document. 2. In communications, the initial contact made between a computer and a remote station receiving a message. 3. In programming, a conditional branch. See also conditional branch.

selective calling n. The capability of a station on a communications line to designate the station that is to receive a transmission.

selector channel n. An input/output data transfer line used by one high-speed device at a time.

selector pen n. See light pen.

select query n. A query that asks a question about the data stored in your tables and returns a result set in the form of a datasheet, all without changing the data.

self-adapting adj. The ability of systems, devices, or processes to adjust their operational behavior to environmental conditions.

self-checking digit n. A digit, appended to a number during its encoding, whose function is to confirm the accuracy of the encoding. See also checksum, parity bit.

self-clocking n. A process in which timing signals are inserted into a data stream rather than being provided by an external source, such as in phase encoding.

self-documenting code n. Program source code that, through its use of a high-level language and descriptive identifiers, can be understood by other programmers without the need for additional comments.

self-extracting archive n. See self-extracting file.

self-extracting file n. An executable program file that contains one or more compressed text or data files. When a user runs the program, it uncompresses the compressed files and stores them on the user s hard drive. See the illustration.

Self-extracting file.

self-modifying code n. Program code, usually object code generated by a compiler or an assembler, that modifies itself during instruction by writing new operation codes, addresses, or data values over existing instructions. See also pure procedure.

self-monitoring analysis and reporting technology system n. See SMART system.

self-organizing map n. See SOM (definition 2).

self-test n. A set of one or more diagnostic tests that a computer or peripheral device (such as a printer) performs on itself. See also power-on self test.

self-validating code n. Program code that can test itself to verify that it behaves correctly, usually by feeding itself a set of standard input values and testing the results against a set of expected output values.

semantic error n. An error in meaning; a statement in a program that is syntactically correct (legal) but functionally incorrect. See also logic, semantics (definition 1), syntax.

semantics n. 1. In programming, the relationship between words or symbols and their intended meanings. Programming languages are subject to certain semantic rules; thus, a program statement can be syntactically correct but semantically incorrect; that is, a statement can be written in an acceptable form and still convey the wrong meaning. See the illustration. See also syntax. 2. In artificial-intelligence research, the capacity of a network to represent relationships among objects, ideas, or situations in a humanlike way. Compare syntax.

Semantics.

semaphore n. In programming, a signal a flag variable used to govern access to shared system resources. A semaphore indicates to other potential users that a file or other resource is in use and prevents access by more than one user. See also flag (definition 1).

Semicon n. Short for Semiconductors Equipment and Material International Conference. A series of international conferences sponsored by the Semiconductors Equipment and Material International (SEMI), a trade group for the international semiconductor industry. The conference provides members with up-to-date information on issues affecting the semiconductor industry and provides SEMI members with a forum for showcasing products and services.

semiconductor n. A substance, commonly silicon or germanium, whose ability to conduct electricity falls between that of a conductor and that of a nonconductor (insulator). The term is used loosely to refer to electronic components made from semiconductor materials.

send vb. To transmit a message or file through a communications channel.

sendmail n. A popular open-source UNIX-based implementation of the Simple Mail Transfer Protocol (SMTP) for delivering e-mail. Written in 1981 by Eric Allman at the University of California at Berkeley, sendmail was the first Internet message transfer agent (MTA).

send statement n. In SLIP and PPP scripting languages, a statement that tells the program that dials an Internet service provider s number (a dialer program) to send certain characters. See also ISP, PPP, scripting language, SLIP.

sensor n. A device that detects or measures something by converting nonelectrical energy to electrical energy. A photocell, for example, detects or measures light by converting it to electrical energy. See also transducer.

sensor glove n. A hand-worn computer input device for virtual-reality environments. The glove translates finger movements by the user to commands for manipulating objects in the environment. Also called: data glove. See also virtual reality.

SEPP n. Acronym for Software Engineering for Parallel Processing. A project of nine European universities and research institutions to develop tools for the development of parallel application programs for distributed memory multiprocessors.

sequence n. An ordered arrangement, as in a set of numbers, such as the Fibonacci sequence. See also Fibonacci numbers.

sequence check n. A process that verifies that data or records conform to a particular order. Compare completeness check, consistency check, duplication check.

Sequenced Packet Exchange n. See SPX (definition 1).

sequential access n. A method of storing or retrieving information that requires the program to start reading at the beginning and continue until it finds the desired data. Sequential access is best used for files in which each piece of information is related to the information that comes before it, such as mailing list files and word processing documents. Also called: serial access. See also indexed sequential access method. Compare random access.

sequential algorithm n. An algorithm in which each step must occur in a particular order. See also algorithm. Compare parallel algorithm.

sequential execution n. The act of executing routines or programs in a linear sequence. Compare concurrent execution.

sequential logic element n. A logic circuit element that has at least one input and one output and in which the output signal depends on the present and past states of the input signal or signals.

sequential processing n. 1. The processing of items of information in the order in which they are stored or input. 2. The execution of one instruction, routine, or task followed by the execution of the next in line. Compare multiprocessing, parallel processing, pipelining (definition 1).

sequential search n. See linear search.

serial adj. One by one. For example, in serial transmission, information is transferred one bit at a time; a serial computer has only one arithmetic logic unit, which must execute the whole program one step at a time. Compare parallel (definition 3).

serial access n. See sequential access.

serial adder n. A circuit that adds two numbers one bit position (one digit place) at a time.

serial communication n. The exchange of information between computers or between computers and peripheral devices one bit at a time over a single channel. Serial communications can be synchronous or asynchronous. Both sender and receiver must use the same baud rate, parity, and control information. See also baud rate, parity, start bit, stop bit.

Serial Infrared n. A system developed by Hewlett-Packard for transmitting data between two devices up to 1 meter apart using an infrared light beam. Infrared ports on the receiving and the sending devices must be aligned. Generally, Serial Infrared is used with laptops and many notebook computers, as well as with peripherals such as printers. Acronym: SIR. See also infrared port.

serial interface n. A data transmission scheme in which data and control bits are sent sequentially over a single channel. In reference to a serial input/output connection, the term usually implies the use of an RS-232 or RS-422 interface. See also RS-232-C standard, RS-422/423/449. Compare parallel interface.

serialize vb. To change from parallel transmission (byte by byte) to serial transmission (bit by bit). Compare deserialize.

SerialKey device n. Enables you to attach an alternative input device (also called an augmentative communication device) to your computer s serial port. This feature is designed for people who are unable to use the computer s standard keyboard and mouse.

SerialKeys n. A feature of Windows 9x, Windows NT, Windows 2000, and Windows XP that, in conjunction with a communications aid interface device, allows keystrokes and mouse controls to be accepted through a computer s serial port.

Serial Line Internet Protocol n. See SLIP.

serial mouse n. A pointing device that attaches to the computer through a standard serial port. See also mouse. Compare bus mouse.

serial port n. An input/output location (channel) that sends and receives data to and from a computer s central processing unit or a communications device one bit at a time. Serial ports are used for serial data communication and as interfaces with some peripheral devices, such as mice and printers.

serial port adapter n. An interface card or device that either provides a serial port or converts a serial port to another use. See also adapter, serial port.

serial printer n. A printer connected to the computer via a serial interface (commonly RS-232-C or compatible). Connectors for this type of printer vary widely, which is one reason they are less popular than parallel printers among those who use IBM and IBM-compatible PCs. Serial printers are standard for Apple computers. See also DB connector, serial, serial transmission. Compare parallel printer.

serial processing n. See sequential processing (definition 2).

Serial Storage Architecture n. See SSA.

serial transmission n. The transfer of discrete signals one after another. In communications and data transfer, serial transmission involves sending information over a single line one bit at a time, as in modem-to-modem connections. Compare parallel transmission.

series circuit n. A circuit in which two or more components are linked in series. All the current passes through each component in a series circuit, but the voltage is divided among the components. See the illustration. Compare parallel circuit.

Series circuit.

serif¹ adj. Marked by the use of serifs. For example, Goudy is a serif typeface, whereas Helvetica is a sans serif typeface. See the illustration. See also serif. Compare sans serif.

Serif. A serif typeface (top) and a sans serif typeface (bottom).

serif² n. Any of the short lines or ornaments at the ends of the strokes that form a typeface character.

server n. 1. On a local area network (LAN), a computer running administrative software that controls access to the network and its resources, such as printers and disk drives, and provides resources to computers functioning as workstations on the network. 2. On the Internet or other network, a computer or program that responds to commands from a client. For example, a file server may contain an archive of data or program files; when a client submits a request for a file, the server transfers a copy of the file to the client. See also application server (definitions 1 and 2), client/server architecture. Compare client (definition 3).

server appliance n. A device designed to deliver one or more specific network services in a single turnkey package that includes both hardware and software. All necessary programs are preinstalled on a server appliance, which has minimal, simplified options and controls. Server appliances can be used to complement or replace traditional servers on a network and can provide such services as file and printer sharing and Internet connectivity. Also called: appliance. See also information appliance.

server-based application n. A program that is shared over a network. The program is stored on the network server and can be used at more than one client machine at a time.

server cluster n. A group of independent computer systems, known as nodes, working together as a single system to ensure that mission-critical applications and resources remain available to clients. A server cluster is the type of cluster that Cluster service implements. See also cluster.

server control n. See ASP.NET server control.

server error n. A failure to complete a request for information through HTTP that results from an error at the server rather than an error by the client or the user. Server errors are indicated by HTTP status codes beginning with 5. See also HTTP, HTTP status codes.

server farm n. A centralized grouping of network servers maintained by an enterprise or, often, an Internet service provider (ISP). A server farm provides a network with load balancing, scalability, and fault tolerance. Individual servers may be connected in such a way that they appear to represent a single resource.

serverlet n. See servlet.

Server Message Block n. See SMB.

server push-pull n. A combination of Web client/server techniques individually called server push and client pull. In server push, the server loads data to the client, but the data connection stays open. This allows the server to continue sending data to the browser as necessary. In client pull, the server loads data to the client, but the data connection does not stay open. The server sends an HTML directive to the browser telling it to reopen the connection after a certain interval to get more data or possibly to open a new URL. See the illustration. See also HTML, server (definition 2), URL.

Server push-pull.

server-side include n. A mechanism for including dynamic text in World Wide Web documents. Server-side includes are special command codes that are recognized and interpreted by the server; their output is placed in the document body before the document is sent to the browser. Server-side includes can be used, for example, to include the date/time stamp in the text of the file. Acronym: SSI. See also server (definition 2).

service n. 1. A customer-based or user-oriented function, such as technical support or network provision. 2. In reference to programming and software, a program or routine that provides support to other programs, particularly at a low (close to the hardware) level. 3. In networking, specialized, software-based functionality provided by network servers for example, directory services that provide the network equivalent of phone books needed for locating users and resources. See also utility.

Service Advertising Protocol n. A method used by a service-providing node in a network (such as a file server or application server) to notify other nodes on the network that it is available for access. When a server boots, it uses the protocol to advertise its service; when the same server goes off line, it uses the protocol to announce that it is no longer available. Acronym: SAP. See also server (definition 1).

service bureau n. 1. A company that provides various services related to publishing, such as prepress production, desktop publishing, typesetting, imagesetting, and optical scanning of graphics. 2. An organization that provides data processing services and access to software packages for a fee.

service provider n. See ISP.

servlet or servelet n. A small Java program that runs on a server. The term is a companion to applet, a Java program that usually runs on the client. Servlets perform lightweight Web services, such as redirecting a Web user from an outdated address to the correct page tasks traditionally handled by CGI (Common Gateway Interface) applications. Because servlets are automatically threaded and highly responsive, they execute quickly, thereby reducing system overhead. Also called: serverlet. See also applet, CGI.

servlet container n. In Sun Microsystems s J2EE network platform, a container that decodes requests, formats responses, and provides the network services over which requests and responses are sent. All servlet containers must support HTTP as a protocol for requests and responses, but they may also support additional request-response protocols such as HTTPS. See also container, HTTP, HTTPS, J2EE.

servo n. The part of a servomechanism, controlled by the servomechanism s feedback circuit, that produces the final mechanical output. Also called: servomotor. See also servomechanism.

servomechanism n. A control system in which the final output is mechanical movement. A servomechanism uses feedback to control the position, velocity, or acceleration of a mechanical component. Also called: servo system.

servomotor n. See servo.

servo system n. See servomechanism.

session n. 1. The time during which a program is running. In most interactive programs, a session is the time during which the program accepts input and processes information. 2. In communications, the time during which two computers maintain a connection. 3. A specific protocol layer in the ISO/OSI reference model that manages communication between remote users or processes. See also ISO/OSI reference model, session layer.

session bean n. In the Java programming language and J2EE network platform, an enterprise bean that is created by a client and usually exists only for the duration of a single client/server session. It performs operations, such as calculations or accessing a database, for the client. While a session bean may be transactional, it is not recoverable should a system crash occur. Session bean objects can either be stateless or can maintain conversational state across methods and transactions. If a session bean maintains state, the Enterprise JavaBean (EJB) container manages this state if the object must be removed from memory. However, the session bean object itself must manage its own persistent data. See also EJB, stateless.

session layer n. The fifth of seven layers in the ISO/OSI reference model. The session layer handles the details that must be agreed on by the two communicating devices. See the illustration. See also ISO/OSI reference model.

Session layer.

set¹ n. In printing and display, a group of related characters, such as a character set. See also character set.

set² vb. 1. To change the value of a bit to 1. 2. To establish a particular condition, such as setting tab stops, setting a counter to 0, or setting a breakpoint. See also breakpoint.

SET protocol n. See Secure Electronics Transactions protocol.

settling time n. The time required for a disk drive s read/write head to stabilize over a new location on the disk after being moved.

set-top box n. A device that converts a cable TV signal to an input signal to the TV set. Set-top boxes can be used to access the World Wide Web and are a type of information appliance. See also information appliance.

setup n. 1. A computer along with all its devices. 2. The procedures involved in preparing a software program or application to operate within a computer.

setup program n. 1. A built-in BIOS program for reconfiguring system parameters to accommodate a new disk drive. See also BIOS. 2. See installation program.

setup string n. See control code.

setup wizard n. In Windows, a utility that asks users a structured series of questions and gives them options to aid the process of installing a new program.

seven-segment display n. A light-emitting diode (LED) display or liquid crystal display (LCD) that can show any of the 10 decimal digits. The seven segments are the seven bars that form a numeral 8 as in a calculator display.

sex changer n. See gender changer.

sfx n. A computer language used to generate digital audio effects and synthesizer instrument audio. It is a superset of the MPEG-4 standard SAOL audio compiler language. Sfx provides professional-quality audio synthesis, real-time MIDI and audio generation, and fully customizable instruments and effects. Because the sfx compiler is a C++ front-end compiler, code is converted to C++ and then compiled into executable orchestras that are used to generate real-time audio. As a result, the current release of sfx requires that Microsoft Visual C++ be installed on the system on which sfx is running. See also C++, compiler, MIDI, MPEG-4, SAOL, Visual C++.

.sgm n. The MS-DOS/Windows 3.x file extension that identifies files encoded in Standard Generalized Markup Language (SGML). Because MS-DOS and Windows 3.x cannot recognize file extensions longer than three letters, the .sgml extension is truncated to three letters in those environments. See also SGML.

.sgml n. The file extension that identifies files encoded in Standard Generalized Markup Language. See also SGML.

SGML n. Acronym for Standard Generalized Markup Language. An information management standard adopted by the International Organization for Standardization (ISO) in 1986 as a means of providing platform- and application-independent documents that retain formatting, indexing, and linked information. SGML provides a grammarlike mechanism for users to define the structure of their documents and the tags they will use to denote the structure in individual documents. See also ISO.

SGRAM n. See synchronous graphics RAM.

sh n. See Bourne shell.

SHA n. Acronym for Secure Hash Algorithm. A technique that computes a 160-bit condensed representation of a message or data file, called a message digest. The SHA is used by the sender and the receiver of a message in computing and verifying a digital signature, for security purposes. See also algorithm, digital signature.

shade¹ n. A particular color variation produced by mixing black with a pure color. See also brightness, IRGB.

shade² vb. To give added dimension to an image by including changes in appearance caused by light and shadow. See also color model.

shadow mask n. A type of mask used in cathode ray tube (CRT) monitors in which an opaque sheet perforated by tiny pinholes ensures that the electron beam for a particular color strikes only the phosphor it is supposed to illuminate. Like the aperture grill, which relies on vertical stripes, and the slot mask, which is based on elliptical openings, a shadow mask helps create a clear, sharp image by narrowly focusing the electron beam. See also CRT, mask (definition 2). Compare aperture grill, slot mask.

shadow memory n. A technique employed by the BIOS in some 80x86-based computers to copy the system s ROM BIOS routines into an unused section of RAM during the computer s startup process. This helps boost system performance by diverting system requests for the BIOS routines to their shadow copies. Also called: shadow RAM, shadow ROM.

shadow print n. A style applied to text in which a duplicate of each character is shifted, typically down and to the right, to create a shadow effect. See the illustration.

Shadow print.

shadow RAM n. See shadow memory.

shadow ROM n. See shadow memory.

share vb. To make files, directories, or folders accessible to other users over a network.

shared assembly n. An assembly that can be referenced by more than one application. An assembly must be explicitly built to be shared by giving it a cryptographically strong name. See also private assembly, strong name.

shared directory n. See network directory.

shared folder n. On a Macintosh computer connected to a network and running System 6.0 or higher, a folder that a user has made available to others on the network. A shared folder is analogous to a network directory on a PC. See also network directory.

shared logic n. The use, by multiple circuits or software routines, of common circuits or routines to implement an operation.

shared medium n. The communications medium shared by network nodes; essentially, the network bandwidth.

shared memory n. 1. Memory accessed by more than one program in a multitasking environment. 2. A portion of memory used by parallel-processor computer systems to exchange information. See also parallel processing.

shared name n. See strong name.

shared network directory n. See network directory.

shared printer n. A printer that receives input from more than one computer.

shared resource n. 1. Any device, data, or program used by more than one device or program. 2. On a network, any resource made available to network users, such as directories, files, and printers.

SharePoint team Web site n. A customizable Web site with features that help a team work together. The default site has pages for document libraries, announcements, and team events. Only members, specified by the site creator, can use the site.

shareware n. Copyrighted software that is distributed on a try-before-you-buy basis. Users who want to continue using the program after the trial period are encouraged to send a payment to the program s author. Compare free software, freeware, public-domain software.

sharpness n. See resolution (definition 1).

sheet n. A feature for handling dialog boxes included in the Mac OS X Aqua interface. When the user chooses to save or print a document, a translucent sheet emerges from the window title bar and remains attached to that window even if it is moved to the background. The sheet allows the user to continue working in the window, or in other windows, without closing the sheet.

sheet-fed scanner n. A scanner with a single-sheet feed mechanism, in which sheets of paper are pulled in by the scanner and scanned as they pass over a stationary scanning mechanism. Sheet-fed scanners allow for automatic scanning of multiple-sheet documents. See also scanner. Compare drum scanner, flatbed scanner, handheld scanner.

sheet feeder n. A device that accepts a stack of paper and feeds it to a printer one page at a time.

shelfware n. Software that has been unsold or unused for a long time, and so has remained on a retailer s or user s shelf.

shell¹ n. A piece of software, usually a separate program, that provides direct communication between the user and the operating system. Examples of shells are Macintosh Finder and the MS-DOS command interface program COMMAND.COM. See also Bourne shell, C shell, Finder, Korn shell. Compare kernel.

shell² vb. See shell out.

shell account n. A computer service that permits a user to enter operating-system commands on the service provider s system through a command-line interface (usually one of the UNIX shells) rather than having to access the Internet through a graphical user interface. Shell accounts can provide Internet access through character-based tools such as Lynx for browsing the World Wide Web. See also shell¹.

shell archive n. In UNIX and GNU, a collection of compressed files that has been prepared for transmission by an e-mail service using the shar command.

shell out vb. To obtain temporary access to the operating-system shell without having to shut down the current application and return to that application after performing the desired shell function. Many UNIX programs allow the user to shell out; the user can do the same in windowing environments by switching to the main system window.

shell script n. A script executed by the command interpreter (shell) of an operating system. The term generally refers to scripts executed by the Bourne, C, and Korn shells on UNIX platforms. Also called: batch file. See also batch file, script, shell¹.

Shell sort n. A programming algorithm used for ordering data in which data are sorted in subsets so that the process works its way from unsorted to progressively more sorted. Named after its inventor, Donald Shell, it is faster than the bubble sort and the insertion sort. See also algorithm. Compare bubble sort, insertion sort.

Sherlock n. An advanced search mechanism included with the Macintosh OS. Sherlock provides the ability to search multiple Internet search engines simultaneously and incorporates the Macintosh Find File interface for searches of local volumes. Additional plug-ins can expand the number of search engines available for access and increase search options.

shielded twisted-pair wiring n. See twisted-pair wiring.

shift vb. In programming, to move the bit values one position to the left or right in a register or memory location. See also end-around shift. Compare rotate (definition 2).

Shift+click or Shift click vb. To click the mouse button while holding down the Shift key. Shift+clicking performs different operations in different applications, but its most common use in Windows is to allow users to select multiple items in a list, for example, to select a number of files for deletion or copying.

Shift key n. A keyboard key that, when pressed in combination with another key, gives that key an alternative meaning; for example, producing an uppercase character when a letter key is pressed. The Shift key is also used in various key combinations to create nonstandard characters or to perform special operations. The term is adapted from usage in relation to manual typewriters, in which the key physically shifted the carriage to print an alternative character. See also Caps Lock key.

Shift-PrtSc n. See Print Screen key.

shift register n. A circuit in which all bits are shifted one position at each clock cycle. It can be either linear (a bit is inserted at one end and lost at the other during each cycle) or it can be cyclic or looped (the lost bit is inserted back at the beginning). See also register, shift.

Shockwave n. A format for multimedia audio and video files within HTML documents, created by Macromedia, which markets a family of Shockwave servers and plug-in programs for Web browsers. See also HTML.

shopping cart n. In e-commerce programs, a file in which an online customer stores information on potential purchases until ready to order. Usually represented on screen with a drawing of a shopping cart, the virtual shopping cart provides a recognizable point of reference to users new to the e-commerce experience. See also e-commerce.

short card n. A printed circuit board that is half as long as a standard-size circuit board. Also called: half-card. See also printed circuit board.

short-circuit evaluation n. A form of expression evaluation that guarantees that Boolean expressions will be evaluated only far enough to determine their value. See also AND, Boolean operator, OR.

shortcut n. In Windows 9x, Windows XP, Windows NT 4, and Windows 2000, an icon on the desktop that a user can double-click to immediately access a program, a text or data file, or a Web page. See also symbolic link.

shortcut key n. See accelerator.

short-haul adj. Of or pertaining to a communications device that transmits a signal over a communications line for a distance less than approximately 20 miles. Compare long-haul.

short message service n. Service for wireless phones that allows users to send and receive brief messages consisting of text and numbers. Acronym: SMS.

shout vb. To use ALL CAPITAL LETTERS for emphasis in e-mail or a newsgroup article. Excessive shouting is considered a violation of netiquette. A word can be more acceptably emphasized by placing it between *asterisks* or _underscores_. See also netiquette.

shovelware n. A commercially sold CD-ROM containing a miscellaneous assortment of software, graphic images, text, or other data that could otherwise be obtained at little or no cost, such as freeware or shareware from the Internet and BBSs or public-domain clip art. See also BBS (definition 1), freeware, shareware.

ShowSounds n. In Windows 9x and Windows NT 4, a global flag that instructs application programs to provide some kind of visual indication that the program is generating a sound in order to alert users with hearing impairments or those in a noisy location such as a factory floor.

shredder n. An application designed to completely destroy digital data so it cannot be reconstructed with file recovery software.

shrinkwrap agreement n. A contract or license in or on a software box or package that sets forth conditions for use of the software. Typically, a shrinkwrap agreement states that a user accepts the terms of the agreement when he or she opens the box. A shrinkwrap agreement is a print version of an End-User License Agreement. Also called: box-top license. See also End-User License Agreement. Compare clickwrap agreement.

shrink-wrapped adj. Boxed and sealed in clear plastic film for commercial distribution. Use of the term implies a final version of a product as opposed to a beta version. See also beta¹.

SHS virus n. Any of a class of viruses that infect a user s system by hiding in files with an .shs extension. These viruses typically spread through e-mail attachments. A widely distributed e-mail warning cautions readers to beware of the SHS virus, but no one specific virus by that name exists.

SHTML n. Short for server-parsed HTML. Hypertext Markup Language (HTML) text that contains embedded server-side include commands. SHTML documents are fully read, parsed, and modified by the server before being passed to the browser. See also HTML, server-side include.

S-HTTP or SHTTP n. Acronym for Secure Hypertext Transfer Protocol. An extension to HTTP that supports various encryption and authentication measures to keep all transactions secure from end to end. S-HTTP is designed to ensure the security of individual transmissions over the Internet and has been approved as a standard by the Internet Engineering Task Force (IETF). S-HTTP should not be confused with HTTPS, a Netscape-developed technology based on SSL (Secure Sockets Layer). HTTPS is also designed to ensure secure transmissions, but does so between communicating computers rather than on a message-by-message basis. Also called: Secure HTTP. See also SSL.

shut down vb. To close a program or an operating system in a manner ensuring that no data is lost.

sibling n. A process or node in a data tree that is descended from the same immediate ancestor(s) as other processes or nodes. See also generation (definition 2), node (definition 3).

sideband n. The upper or lower portion of a modulated carrier wave. One portion can be processed while the other is used to carry separate data, a technique that doubles the amount of information that can be carried over a single line. See the illustration.

Sideband.

sidebar n. A block of text placed to the side of the main body of text in a document, often set off by a border or other graphic element.

side-by-side execution n. The ability to install and use multiple versions of an assembly in isolation at the same time. This can occur on the same machine, or in the same process or application domain. Side-by-side execution can apply to applications and components as well as the components of the .NET Framework. Allowing assemblies to run side-by-side is essential to support robust versioning in the common language runtime.

side effect n. Any change of state caused by a subroutine, such as a routine that reads a value from a file and advances the current file position.

side head n. A heading placed in the margin of a printed document and top-aligned with the body text, rather than being vertically aligned with text, as is a normal head.

sieve of Eratosthenes n. An algorithm for finding prime numbers. It is often used as a benchmark in testing the speed of a computer or programming language. See also benchmark.

.sig n. A file extension for a signature file for e-mail or Internet newsgroup use. The contents of this file are automatically appended to e-mail correspondence or newsgroup articles by their respective client software. See also signature file (definition 1).

SIG n. Acronym for special interest group. An e-mail online discussion group or a group of users who meet and share information, especially one of the groups supported by the Association for Computing Machinery (ACM), such as SIGGRAPH for computer graphics.

SIGGRAPH n. Short for Special Interest Group on Computer Graphics, a part of the Association for Computing Machinery (ACM).

sigmoid function n. A kind of S-shaped mathematical function arising in many dynamical systems, including neural networks, because it is the solution to a first-order differential equation. It typically maps a real value, which may be arbitrarily large in magnitude (positive or negative), to another real value, which lies within some narrow range. The sigmoid function, in neural network computation literature, is also sometimes referred to as the logistic function. The reason for its prevalence is that it is thought to resemble the probability that a true neuron generates as an action potential in response to particular input and output. See also artificial intelligence, neural network.

sign n. The character used to indicate a positive or negative number. In assembly-level programming, the sign is indicated by the sign bit accompanying the number. See also sign bit.

signal n. 1. Any electrical quantity, such as voltage, current, or frequency, that can be used to transmit information. 2. A beep or tone from a computer s speaker or a prompt displayed on screen that tells a user that the computer is ready to receive input.

signal converter n. A device or circuit that converts a signal from one form to another, such as analog to digital, or pulse code modulation to frequency modulation.

signal-to-noise ratio n. The amount of power, measured in decibels, by which the signal exceeds the amount of channel noise at the same point in transmission. Abbreviation: S/N. See also noise (definition 2).

signature n. 1. A sequence of data used for identification, such as text appended to an e-mail message or a fax. 2. A unique number built into hardware or software for authentication purposes.

signature block n. A block of text that an e-mail client or a newsreader automatically places at the end of every message or article before the message or article is transmitted. Signature blocks typically contain the name, e-mail address, and affiliation of the person who created the message or article.

signature file n. 1. A file that contains information inserted by a user and automatically appended to e-mail correspondence or newsgroup articles by client software. A signature file typically contains the name or nickname of the user and might include such information as the user s e-mail address, Web page, company, or job title. 2. A file that updates an antivirus program so that the program recognizes signatures of new viruses and removes the viruses from the user s computer. See also antivirus program, virus signature.

sign bit n. The most significant, or leftmost, bit of a number field, usually set to 1 if the number is negative.

sign extension n. See sign bit.

significand n. See mantissa.

significant digits n. The sequence from the first nonzero digit to the last digit in a number (the last nonzero digit in an integer), used to express the number s precision (for example, 12,300 has three significant digits, and 0.000120300 has six). See also floating-point notation.

sign off vb. See log off.

sign on vb. See log on.

sign propagation n. See sign bit.

SIIA n. Acronym for Software & Information Industry Association. A nonprofit trade association representing over 1200 high-tech companies worldwide and charged with watching over the interests of the software and digital content industry. The SIIA was formed in 1999 when the Software Publishers Association (SPA) merged with the Information Industry Association (IIA). The SIIA focuses on three areas: providing information and forums in which to distribute information to the high-tech industry; protection in the form of an antipiracy program geared to help members enforce their copyrights; and promotion and education.

silica gel n. A desiccant (moisture-absorbing substance) often packaged with optical or electronic equipment.

silicon n. A semiconductor used in many devices, especially microchips. Silicon, with atomic number 14 and atomic weight 28, is the second most common element in nature. Compare silicone.

Silicon Alley n. The Manhattan, New York, metropolitan area. Originally the term referred to the area of Manhattan below 41st Street, which had a heavy concentration of technology companies, but it now includes the entire island, reflecting the number of businesses involved in computer technology in that area. The name was inspired by Silicon Valley, the area of northern California that is home to many technology firms. See also Silicon Valley.

silicon chip n. An integrated circuit that uses silicon as its semiconductor material.

silicon-controlled rectifier n. A semiconductor rectifier whose conductance can be controlled by a gate signal. Acronym: SCR. See also gate (definition 1), rectifier.

silicon dioxide n. An insulator used to form thin insulating layers in some types of semiconductors; also the primary component of glass.

silicone n. A polymer in which silicon and oxygen are major components. Silicone is an excellent electrical insulator and conducts heat well. Compare silicon.

silicon foundry n. A factory or machine used to create wafers of crystalline silicon.

silicon on insulator n. See SOI.

silicon-on-sapphire n. A method of fabricating semiconductors in which the semiconductor devices are formed in a thin single layer of silicon that has been grown on an insulating substrate of synthetic sapphire. Acronym: SOS.

Silicon Valley n. The region of California south of San Francisco Bay, otherwise known as the Santa Clara Valley, roughly extending from Palo Alto to San Jose. Silicon Valley is a major center of electronics and computer research, development, and manufacturing. See the illustration.

Silicon Valley.

Silicorn Valley n. Clusters of high-tech companies headquartered in small cities in the Midwestern United States, particularly in areas of rural Iowa.

SIM n. See Society for Information Management.

SIM card n. Short for Subscriber Identity Module card. A smart card designed for use with GSM (Global System for Mobile Communications) mobile phones. SIM cards contain chips that store a subscriber s personal identifier (SIM PIN), billing information, and data (names, phone numbers). See also Global System for Mobile Communications, smart card (definition 2).

SIMD n. Acronym for single-instruction, multiple-data stream processing. A category of parallel-processor computer architecture in which one instruction processor fetches instructions and distributes orders to several other processors. See the illustration. See also parallel processing. Compare MIMD.

SIMD.

SIMM n. Acronym for single inline memory module. A small circuit board designed to accommodate surface-mount memory chips.

Simple API for XML n. See SAX.

Simple Authentication and Security Layer n. See SASL.

Simple Control Protocol n. See SCP.

Simple Mail Transfer Protocol n. A TCP/IP protocol for sending messages from one computer to another on a network. This protocol is used on the Internet to route e-mail. Acronym: SMTP. See also communications protocol, TCP/IP. Compare CCITT X series, Post Office Protocol.

Simple Network Management Protocol n. See SNMP.

Simple Object Access Protocol n. See SOAP.

simplex n. Communication that takes place only from sender to receiver. Compare duplex² (definition 1), half-duplex.

simplex transmission n. See simplex.

SIMULA n. Short for simulation language. A general-purpose programming language based on ALGOL 60, with special features designed to aid the description and simulation of active processes. Visual C++ is based on aspects of this language.

simulation n. The imitation of a physical process or an object by a program that causes a computer to respond mathematically to data and changing conditions as though it were the process or object itself. See also emulator, modeling (definition 1).

simultaneous access n. See parallel access.

simultaneous processing n. 1. True multiple-processor operation in which more than one task can be processed at a time. See also multiprocessing, parallel processing. 2. Loosely, concurrent operation in which more than one task is processed by dividing processor time among the tasks. See also concurrent, multitasking.

sine wave n. A uniform, periodic wave often generated by an object that vibrates at a single frequency. See the illustration. Compare square wave.

Sine wave.

single attachment station n. An FDDI node that connects to the primary ring through a concentrator. Compare dual attachment station.

single-board adj. Of or pertaining to a computer that occupies only one circuit board, usually with no capacity for additional boards.

single-density adj. Of or pertaining to a disk that is certified only for use with frequency modulation (FM) recording. A single-density disk can store much less data than a disk using modified FM encoding or run-length limited encoding. See also modified frequency modulation encoding, run-length limited encoding.

Single Image Random Dot Stereogram n. See auto stereogram.

Single Image Stereograms n. See autostereogram.

single inline memory module n. See SIMM.

single inline package n. See SIP.

single inline pinned package n. See SIP.

single-instruction, multiple-data stream processing n. See SIMD.

single-line digital subscriber line n. See SDSL.

single-precision adj. Of or pertaining to a floating-point number having the least precision among two or more options commonly offered by a programming language, such as single-precision versus double-precision. See also floating-point notation, precision (definition 2). Compare double-precision.

single-sided adj. Of or pertaining to a floppy disk in which data can be stored on only one side.

single sign-on n. A system enabling a user to enter one name and password to log on to different computer systems or Web sites. Single sign-on is also available for enterprise systems so a user with a domain account can log on to a network once, using a password or smart card, and thereby gain access to any computer in the domain. See also domain, smart card (definition 1).

single step vb. To execute a program one step at a time, usually within the context of a debugger. See also debugger.

single switch device n. An assistive computer technology for people with mobility impairments. A single switch device allows users to interact with a computer by using slight body movements.

single threading n. 1. Within a program, the running of a single process at a time. 2. A condition in which each leaf node of a tree data structure contains a pointer to its parent. See also node (definition 3), pointer (definition 1), threading.

single-user computer n. A computer designed for use by a single individual; a personal computer. Compare multi user system.

sink n. A device or part of a device that receives something from another device. See also data sink, heat sink.

SIP n. Acronym for single inline package. A type of housing for an electronic component in which all leads (connections) protrude from one side of the package. Also called: single inline pinned package. Compare DIP.

SIPP n. Acronym for single inline pinned package. See SIP.

SIR n. See Serial Infrared.

SirCam worm n. A malicious worm that combines fast infection with the potential to deliver multiple malicious payloads. SirCam spreads through multiple means, both by mailing infected personal files from a compromised disk to other potential victims and through Windows network shares on unprotected machines. One time in 20 SirCam deletes the contents of the infected drive, and one time in 50 it fills all free space on the disk with trash data. SirCam was discovered in mid-2001 and has reappeared regularly since that time.

SIRDS n. Acronym for Single Image Random Dot Stereogram. See autostereogram.

SIS n. Acronym for Single Image Stereogram. See autostereogram.

.sit n. The file extension for a Macintosh file compressed with StuffIt. See also StuffIt.

site n. See Web site.

site license n. A purchase agreement for using multiple copies of the same software at a business or an institution, usually at a volume discount.

size box n. A control in the upper right corner of the frame of a window on the Macintosh screen. When the user clicks the size box, the window toggles between the size the user has set for it by dragging and the maximum size. Compare Maximize button.

skew n. The difference between what is and what should be for example, the misalignment of a page that prevents accurate reproduction, or the difference between input and output when circuits do not respond evenly to a propagated signal.

skin n. An alternative graphical interface for an operating system (OS) or a software program. A skin customizes the look of the OS or program but does not affect its functionality. Programs that allow the use of skins usually make standards available for the creation and distribution of new skins. See also graphical user interface.

skin mode n. An operational state of various media players, including RealPlayer, Winamp, and Windows Media Player, in which the user interface is customized and displayed as a skin. Often some features of the player are not accessible in skin mode. Skin mode was called compact mode in Windows Media Player 7. See also full mode.

Skutch box n. A slang term for a device manufactured by Skutch Electronics, Inc., that simulates the functioning of a telephone line with a good connection. Telephone line simulators are used to test telecommunications systems and devices.

skyscraper n. One of several larger formats for online ads developed to replace traditional banner ads on the Internet. See avalanche ad.

slave n. Any device, including a computer, that is controlled by another computer, referred to as the master. See also master/slave arrangement.

sleep¹ n. 1. In a multiprocessing environment, a temporary state of suspension during which a process remains in memory so that some event, such as an interrupt or a call from another process, can awaken it. 2. In programming, a state of suspension caused by a loop statement that creates an intentional delay.

sleep² vb. To suspend operation without terminating.

sleep mode n. A power management mode that shuts down all unnecessary computer operations to save energy after it has received no input or other activity for a specified period of time. A computer in sleep mode usually awakens when it receives an input signal from a user or a network, such as a keyboard entry or an incoming call through a modem. Many battery-powered devices, including portable computers, support sleep mode. See also green PC, sleep¹ (definition 1), Suspend command.

sleeve n. See disk envelope.

slice n. See time slice.

SLIP n. Acronym for Serial Line Internet Protocol. A data link protocol that allows transmission of TCP/IP data packets over dial-up telephone connections, thus enabling a computer or a LAN (local area network) to be connected to the Internet or some other network. It is an older, less secure protocol than the PPP (Point-to-Point Protocol) and does not support dynamic allocation of IP addresses. A newer form of SLIP, known as CSLIP (Compressed SLIP), optimizes transmission of long documents by compressing header information. See also data link, IP. Compare PPP.

SLIP emulator n. Software that mimics a SLIP connection in UNIX shell accounts that do not offer a direct SLIP connection. Many Internet service providers (ISPs) are UNIX based and offer shell accounts to users for Internet access. Like a SLIP connection, the SLIP emulator allows the user to avoid dealing with the ISP s UNIX environment directly when accessing the Internet and to use Internet applications such as graphical Web browsers. See also ISP, shell account, SLIP.

slot n. 1. See expansion slot. 2. An integrated circuit mounting connector designed to connect a microprocessor with a PC s data bus. Currently, only newer models of Intel s Pentium family employ this. See also Pentium, Slot 1, Slot 2.

Slot 1 n. A receptacle on a PC motherboard designed to hold a Pentium II microprocessor. The microprocessor, which is encased in Intel s Single Edge Contact (SEC) packaging, slides into the slot on the motherboard. Slot 1 includes 242 electrical contact points and communicates with the chip s L2 cache at half of the PC s clock speed. Slot 1 replaced socket 7 and socket 8 in Intel architectures, but has been superceded by Slot 2 in newer model Pentiums. See also L2 cache, motherboard, Pentium. Compare Slot 2, socket 7, socket 8.

Slot 2 n. A receptacle on a PC motherboard designed to hold Intel microprocessors beginning with the Pentium II Xeon and including the Pentium III microprocessor. Like Slot 1, Slot 2 is encased in Intel s Single Edge Contact packaging, so it slides easily into the slot on the motherboard. It includes 330 electrical contact points and is slightly wider than Slot 1. It also supports communication between the CPU and the L2 cache at the full clock speed of the PC. See also L2 cache, motherboard, Pentium. Compare Slot 1.

slot mask n. A type of mask used in cathode ray tube (CRT) monitors in which a thin sheet of metal perforated with elliptical holes is used to ensure that the electron beam for a particular color (red, green, or blue) strikes only the phosphor (of the corresponding color) that it is intended to illuminate. The elliptical lozenge-shaped holes in a slot mask place it between a shadow mask, which is based on round openings, and an aperture grill, which is based on vertical strips of metal. Slot masks were introduced by NEC in its CromaClear technology. See also CRT, mask (definition 2). Compare aperture grill, shadow mask.

slot pitch n. The distance, measured horizontally, between phosphor dots of the same color on a cathode ray tube (CRT) display based on slot mask technology. Although the measurements are based on different methods of applying phosphor to the screen surface, slot pitch is comparable to dot pitch, the measurement used with CRTs based on shadow mask technology. See also CRT, mask (definition 2), slot mask. Compare dot pitch, stripe pitch.

slotted-ring network n. A ring network allowing data to be transmitted between data stations in one direction. A slotted-ring network transfers data in predefined time slots (fixed-length portions of a data frame) in the transmission stream over one transmission medium. See also data frame, ring network. Compare token ring network.

SlowKeys n. An accessibility feature built into Macintosh computers and available for DOS and Windows that allows the user to add a delay to the keyboard so that a key must be held down for a certain amount of time before it is accepted. This feature facilitates the use of the keyboard by individuals with poor motor control who might accidentally bump keys when moving around the keyboard.

SLSI n. See super-large-scale integration.

Small Business Server n. A software application developed by Microsoft Corporation to increase the efficiency of Web-based services for small businesses with 50 or fewer personal computers. Small Business Server provides shared Internet access, features for building Web-based customer management and customer communications tools, and additional features that increase productivity by streamlining employee access to files and applications over the Web.

small caps n. A font of capital letters that are smaller than the standard capital letters in that typeface.

Small Computer System Interface n. See SCSI.

small model n. A memory model of the Intel 80x86 processor family that allows only 64 kilobytes (KB) for code and 64 KB for data. See also memory model.

Small Office/Home Office n. See SOHO.

small-scale integration n. A concentration of fewer than 10 components on a single chip. Acronym: SSI. See also integrated circuit.

Smalltalk n. An object-oriented language and development system developed at Xerox Palo Alto Research Center (PARC) in 1980. Smalltalk pioneered many language and user interface concepts that are now widely used in other environments, such as the concept of an object that contains data and routines and on-screen icons that the user can choose to make the computer perform certain tasks. See also object-oriented programming.

smart adj. A synonym for intelligent. See intelligence.

smart cable n. See intelligent cable.

smart card n. 1. In computers and electronics, a circuit board with built-in logic or firmware that gives it some kind of independent decision-making ability. 2. In banking and finance, a credit card that contains an integrated circuit that gives it a limited amount of intelligence and memory.

smart card reader n. A device that is installed in computers to enable the use of smart cards for enhanced security features. See also smart card (definition 2).

smart device n. An electronic device capable of being networked and remotely controlled in a smart home. Smart devices can include appliances, lighting, heating and cooling systems, entertainment systems, and security systems. See also home automation, home network (definition 1), smart home.

smart home n. A home or building wired for networking and home automation. In a smart home, occupants control smart devices programmatically or on command using a home-networking communications protocol. Also called: automated home, digital home, e-home, Internet home, networked home, smart house, wired home. See also home automation, home network (definition 1).

smart house n. See smart home.

smart linkage n. A feature of programming languages that guarantees that routines will always be called with correct parameter types. See also link (definition 1).

smartphone n. A hybrid between a wireless telephone and a personal digital assistant (PDA). Smartphones integrate wireless telephones with many of the personal organizational functions of PDAs, such as calendar, calculator, database, e-mail, wireless Web access, note taking, and other programs common to lightweight palm-style computers. Smartphones may rely on a stylus, keypad, or both for data entry or may use voice recognition technology. See also cell, palmtop, PDA, pen computer, wireless phone.

smart quotes n. In word processors, a function that automatically converts the ditto marks (") produced by most computer keyboards to the inverted commas ( and ) used in typeset text.

SmartSuite n. A suite of business application programs sold by Lotus Development. Lotus SmartSuite includes six programs: Lotus 1-2-3 spreadsheet, Lotus WordPro word processor, Lotus Approach database, Lotus Freelance Graphics presentation software, Lotus Organizer time-management software, and Lotus FastSite Internet/intranet publishing tool. SmartSuite Millennium Edition 9.7 supports collaboration, Web publishing, use of Internet/intranet resources, and customizable document and project organizers. SmartSuite competes with Microsoft Office and WordPerfect Office.

SMART system n. Short for Self-Monitoring Analysis and Reporting Technology system. A system by which technology is used to monitor and predict device performance and reliability. A SMART system employs various diagnostic tests to detect problems with devices, with the object of increasing productivity and protecting data.

smart terminal n. A terminal that contains a microprocessor and random access memory (RAM) and that does some rudimentary processing without intervention from the host computer. Compare dumb terminal.

SMB n. Acronym for Server Message Block. A file-sharing protocol designed to allow networked computers to transparently access files that reside on remote systems over a variety of networks. The SMB protocol defines a series of commands that pass information between computers. SMB uses four message types: session control, file, printer, and message. See also LAN Manager, NetBIOS, Samba.

SMDS n. Acronym for Switched Multimegabit Data Services. A very high-speed, connectionless, packet-switched data transport service that connects LANs (local area networks) and WANs (wide area networks).

SMIL n. Acronym for Synchronized Multimedia Integration Language. A markup language that enables separate elements, including audio, video, text, and still images, to be accessed separately and then integrated and played back as a synchronized multimedia presentation. Based on XML (eXtensible Markup Language), SMIL allows Web authors to define the objects in the presentation, describe their locations onscreen, and determine when they will be played back. The language is based on statements that can be entered with a text editor and was developed under the auspices of the World Wide Web Consortium (W3C). See also markup language, XML.

smiley n. See emoticon.

S/MIME n. Acronym for Secure/Multipurpose Internet Mail Extensions. An Internet e-mail security-oriented protocol that adds public key encryption and support for digital signatures to the widely used MIME e-mail protocol. See also public key encryption.

SMIS n. Acronym for Society for Management Information Systems. See Society for Information Management.

smoke test n. The testing of a piece of hardware after assembly or repairs by turning it on. The device fails the test if it produces smoke, explodes, or has some other unexpected violent or dramatic reaction, even if it appears to work.

smooth vb. 1. To eliminate irregularities in statistical data by some process such as continuous averaging or by removing random (irrelevant) values. 2. In graphics, to remove jagged edges from a figure or line. See also anti-aliasing.

SMP n. Acronym for symmetric multiprocessing. A computer architecture in which multiple processors share the same memory, which contains one copy of the operating system, one copy of any applications that are in use, and one copy of the data. Because the operating system divides the workload into tasks and assigns those tasks to whichever processors are free, SMP reduces transaction time. See also architecture, multiprocessing.

SMP server n. Short for symmetric multiprocessing server. A computer that is designed with the SMP architecture to improve its performance as a server in client/server applications. See also SMP.

SMS n. See Systems Management Server.

SMS n. See short message service.

SMT n. See surface-mount technology.

SMTP n. See Simple Mail Transfer Protocol.

smurf attack n. A form of denial-of-service attack on an Internet server that sends simultaneous echo request packets ( ping packets) to one or more broadcast IP addresses (such as an IRC server), each of which in turn relays the request to as many as 255 individual host computers, with the address of the attack s victim as the forged (spoofed) source address. When the hosts return echo packets to the apparent source of the request, the volume of the responses is enough to disable the network. See also denial of service attack, spoofing.

SNA n. Acronym for Systems Network Architecture. A network model devised by IBM to enable IBM products, including mainframes, terminals, and peripherals, to communicate and exchange data. SNA started out as a five-layer model and was later extended with two additional layers to correspond more closely to the ISO/OSI reference model. More recently, the SNA model was modified to include minicomputers and microcomputers in a specification known as APPC (Advanced Program to Program Communications). See the illustration. See also APPC. Compare ISO/OSI reference model.

SNA. Comparable (not compatible) layers in the SNA and ISO/OSI architechures.

snail mail n. A popular phrase on the Internet for referring to mail services provided by the U.S. Postal Service and similar agencies in other countries. The term has its origins in the fact that regular postal mail is slow compared with e-mail.

snap-in n. 1. See plug-in. 2. A software component that provides system administration and system management capability within the framework of the Microsoft Management Console (MMC) for Windows NT, Windows 2000, and Windows XP. A snap-in (also capitalized as Snap-In) is a COM object that represents one unit of management behavior, the smallest extension available through the MMC. There are two types of snap-ins: stand-alone (not reliant on any other snap-in) and extension (invoked by a parent snap-in). Multiple snap-ins can be combined to create larger management tools.

snapshot n. A copy of main memory or video memory at a given instant, sent to the printer or hard disk. Also called: snapshot dump. See also screen dump.

snapshot program n. A program that performs a trace by taking a snapshot of certain chunks of memory at specified times.

.snd n. A file extension for a type of interchangeable sound file format used on Sun, NeXT, and Silicon Graphics computers, consisting of raw audio data preceded by a text identifier.

sneaker n. An individual employed by a company or organization to test their security by breaking into the employer s network. Information gathered by the sneaker can be used to repair network security weaknesses. See also tiger team.

sneakernet n. Transfer of data between computers that are not networked together. The files must be written onto floppy disks on the source machine, and a person must physically transport the disks to the destination machine.

sniffer n. See packet sniffer.

SNMP n. Acronym for Simple Network Management Protocol. The network management protocol of TCP/IP. In SNMP, agents, which can be hardware as well as software, monitor the activity in the various devices on the network and report to the network console workstation. Control information about each device is maintained in a structure known as a management information block. See also agent (definition 4), TCP/IP.

SNOBOL n. Acronym for String-Oriented Symbolic Language. A string- and text-processing language developed between 1962 and 1967 by Ralph Griswold, David Farber, and I. Polonsky at AT&T Bell Laboratories. See also string.

snow n. 1. In television, temporary distortion of a displayed image caused by interference, usually in a weak signal, that takes the form of random white spots. 2. In computer displays, a specific type of distortion characterized by the blinking on and off of random pixels that occurs when the microprocessor and the display hardware interfere with each other by attempting to use the computer s video memory at the same time.

SOAP n. Acronym for Simple Object Access Protocol. A simple, XML-based protocol for exchanging structured and type information on the Web. The protocol contains no application or transport semantics, which makes it highly modular and extensible.

SOC n. Acronym for system on a chip. A chip integrating computer, microprocessors, and all necessary support components in a single unit. SOC technology is used in firewalls, gateways, specialized servers, and interactive devices like Web pads and vending machines.

social engineering n. The practice of penetrating system security by tricking individuals into divulging passwords and information about network vulnerabilities. Often done by calling the individual on phone and pretending to be another employee of company with a computer-related question.

Society for Information Management n. A professional society based in Chicago for information systems executives, formerly the Society for Management Information Systems. Acronym: SIM.

Society for Management Information Systems n. See Society for Information Management.

socket n. 1. An identifier for a particular service on a particular node on a network. The socket consists of a node address and a port number, which identifies the service. For example, port 80 on an Internet node indicates a Web server. See also port number, sockets API. 2. The receptacle part of a connector, which receives a plug. See also female connector. 3. A receptacle on a PC motherboard into which a microprocessor is plugged. A socket-mounted microprocessor, such as the Pentium, connects to the motherboard through numerous pins on the underside. Newer Intel microprocessors, such as the Pentium II and later, plug into the motherboard through an edge connector along the side of the chip. See also socket 4, socket 5, socket 7, socket 8. Compare Slot 1, Slot 2.

socket 4 n. A 5-volt mounting socket on a PC motherboard designed to hold a Pentium microprocessor operating at 60 MHz or 66 MHz. Socket 4 includes openings for 273 pins. See also Pentium, socket (definition 3). Compare Slot 1, Slot 2, socket 5, socket 7, socket 8.

socket 5 n. A 3.3-volt mounting socket on a PC motherboard designed to hold a Pentium microprocessor operating at the following speeds: 75, 90, 100, 120, 133, 150, 166, 180, and 200 MHz. Socket 5 includes openings for 320 pins. It has been superceded by socket 7, socket 8, slot 1, and slot 2. See also Pentium, socket (definition 3). Compare Slot 1, Slot 2, socket 4, socket 7, socket 8.

socket 7 n. A mounting socket on a PC motherboard designed to hold a microprocessor operating at the following speeds: 150, 166, 180, 200, 210, and 233 MHz. Socket 7 includes openings for 321 pins and operates at two voltages, 2.5 volts at the core and 3.3 volts input/output. It is used with the Pentium MMX chip and competitive microprocessor chips from other manufacturers, such as AMD and Cyrix. See also MMX, Pentium, socket (definition 3). Compare Slot 1, Slot 2, socket 4, socket 5, socket 8.

socket 8 n. A 2.5-volt mounting socket on a PC motherboard designed to hold a Pentium Pro microprocessor. Socket 8 has openings for 387 pins. See also Pentium, socket (definition 3). Compare Slot 1, Slot 2, socket 4, socket 5, socket 7.

sockets API n. An application programming interface implemented to create and use sockets in client/server networking. The most common sockets API is the University of California at Berkeley UNIX/BSD implementation (Berkeley Sockets API), which is the basis for Winsock. See also socket (definition 1).

soc. newsgroups n. Usenet newsgroups that are part of the soc. hierarchy and have the prefix soc. These newsgroups are devoted to discussions of current events and social issues. Soc. newsgroups are one of the seven original Usenet newsgroup hierarchies. The other six are comp., misc., news., rec., sci., and talk. See also newsgroup, traditional newsgroup hierarchy, Usenet.

soft adj. 1. In computing, temporary or changeable. For example, a soft error is a problem from which the system can recover, and a soft patch is a temporary program fix that holds only while the program is running. Compare hard (definition 1). 2. In electronics, characterized by magnetic materials that do not retain their magnetism when a magnetic field is removed. Compare hard (definition 2).

soft boot n. See warm boot.

soft copy n. The temporary images presented on a computer display screen. Compare hard copy.

soft error n. An error from which a program or operating system is able to recover. Compare hard error.

soft font n. See downloadable font.

soft hyphen n. See hyphen.

soft link n. See symbolic link.

softmodem n. See software-based modem.

soft patch n. A fix or modification performed only while the code being patched is loaded into memory, so that the executable or object file is not modified in any way. See also patch¹.

soft return n. A line break inserted in a document by a word processor when the next word in the current line of text would cause the line to overflow into the margin a movable line break. See also wordwrap. Compare hard return.

soft-sectored disk n. A disk, especially a floppy disk, whose sectors have been marked with recorded data marks rather than punched holes. See also index hole. Compare hard-sectored disk.

software n. Computer programs; instructions that make hardware work. Two main types of software are system software (operating systems), which controls the workings of the computer, and applications, such as word processing programs, spreadsheets, and databases, which perform the tasks for which people use computers. Two additional categories, which are neither system nor application software but contain elements of both, are network software, which enables groups of computers to communicate, and language software, which provides programmers with the tools they need to write programs. In addition to these task-based categories, several types of software are described based on their method of distribution. These include packaged software (canned programs), sold primarily through retail outlets; freeware and public domain software, which are distributed free of charge; shareware, which is also distributed free of charge, although users are requested to pay a small registration fee for continued use of the program; and vaporware, software that is announced by a company or individuals but either never makes it to market or is very late. See also application, canned software, freeware, network software, operating system, shareware, system software, vaporware. Compare firmware, hardware, liveware.

Software & Information Industry Association n. See SIIA.

software-based modem n. A modem that uses a general-purpose, reprogrammable digital signal processor chip and RAM-based program memory rather than a dedicated chip with the modem functions burned into the silicon. A software-based modem can be reconfigured to update and change the modem s features and functions.

software bloat n. A software condition caused by the addition of excessive number of possibly unnecessary features and functions as new versions of the software are released. Software bloat is generally assumed to result in long loading times and inordinate resource (memory and storage) requirements. See also bloatware, creeping featurism.

software conversion n. Changing or moving a program designed to run on one computer to run on another. Usually this involves detailed (professional) work on the program itself.

software-dependent adj. Of, pertaining to, or being a computer or device that is tied to a particular program or set of programs developed for it.

software development kit n. See developer s kit.

software engineer n. 1. In general, one who works at the code level with software. Although such engineering can be considered to encompass everything from software design to management and testing, the term is generally considered more or less synonymous with programmer one who actually writes the code. 2. See developer.

software engineering n. The design and development of software. See also programming.

software handshake n. A handshake that consists of signals transmitted over the same wires used to transfer the data, as in modem-to-modem communications over telephone lines, rather than signals transmitted over special wires. See also handshake.

software house n. An organization that develops and supports software for its customers.

software IC n. See software integrated circuit.

software integrated circuit n. An existing software module that can be designed into a program, much as an integrated circuit can be designed into a logic board. Abbreviation: software IC. See also abstract data type, module (definition 1), object-oriented programming.

software interrupt n. A program-generated interrupt that stops current processing in order to request a service provided by an interrupt handler (a separate set of instructions designed to perform the task required). Also called: trap.

software package n. A program sold to the public, ready to run and containing all necessary components and documentation.

software piracy n. See piracy.

software portability n. See portable (definition 1).

software program n. See application.

software protection n. See copy protection.

software publisher n. A business engaged in the development and distribution of computer software.

Software Publishers Association n. See SIIA.

software publishing n. The design, development, and distribution of noncustom software packages.

software rot n. See dead code.

software stack n. See stack.

software suite n. See suite (definition 1).

software tools n. Programs, utilities, libraries, and other aids, such as editors, compilers, and debuggers, that can be used to develop programs.

SOHO n. Acronym for Small Office/Home Office, a term used for home-based and small businesses. The fast-growing SOHO market has sparked a concomitant expansion in computer software and hardware products designed specifically to meet the needs of self-employed individuals or small businesses. See also distributed workplace, telecommuter.

SOI n. Acronym for silicon on insulator. A method used in the construction of microprocessors in which the chip s transistors the tiny circuits that conduct electrical charges are built on a layer of silicon placed on top of a layer of insulating material, such as glass. SOI construction improves speed at the same time it reduces the amount of power required by the microprocessor.

solar cell n. A photoelectric device that produces electrical power when exposed to light. Also called: photovoltaic cell.

Solaris n. A distributed UNIX-based computing environment created by Sun Microsystems, Inc., widely used as a server operating system. Versions of Solaris exist for SPARC computers, 386 and higher Intel platforms, and the PowerPC.

solenoid n. An electromagnetic device that converts electrical energy to mechanical movement, typically consisting of an electromagnet with a movable rod through the center.

solid ink n. Ink manufactured in the form of solid sticks resembling crayons, for use in solid-ink printers. See also solid-ink printer.

solid-ink printer n. A computer printer using solid ink sticks. The ink sticks are heated until they melt, and the molten ink is sprayed onto the page, where it cools and solidifies. See also solid ink.

solid model n. A geometric shape or construction that has continuity in length, width, and depth and is treated by a program as if it had both surface and internal substance. Compare surface modeling, wire-frame model.

solid-state device n. A circuit component whose properties depend on the electrical or magnetic characteristics of a solid substance (as opposed to a gas or vacuum). Transistors, diodes, and integrated circuits are solid-state devices.

solid-state disk drive n. A mass storage device that holds data in RAM rather than in magnetic storage. See also magnetic storage, RAM.

solid-state memory n. Computer memory that stores information in solid-state devices.

solid-state relay n. A relay that depends on solid-state components, rather than mechanical components, to open and close a circuit.

SOM n. 1. Acronym for System Object Model. A language-independent architecture from IBM that implements the CORBA standard. See also CORBA, OMA. 2. Acronym for self-organizing map. A form of neural network in which neurons and their connections are added automatically as needed to develop the desired mapping from input to output.

SONET n. Acronym for Synchronous Optical Network. A high-speed network that provides a standard interface for communications carriers to connect networks based on fiberoptic cable. SONET is designed to handle multiple data types (voice, video, and so on). It transmits at a base rate of 51.84 Mbps, but multiples of this base rate go as high as 2.488 Gbps (gigabits per second).

sort vb. To organize data, typically a set of records, in a particular order. Programs and programming algorithms for sorting vary in performance and application. See also bubble sort, distributive sort, insertion sort, merge sort, quicksort, Shell sort.

sort algorithm n. An algorithm that puts a collection of data elements into some sequenced order, sometimes based on one or more key values in each element. See also algorithm, bubble sort, distributive sort, insertion sort, merge sort, quicksort, Shell sort.

sorter n. A program or routine that sorts data. See also sort.

sort field n. See sort key.

sort key n. A field (commonly called a key) whose entries are sorted to produce a desired arrangement of the records containing the field. See also field (definition 1), primary key, secondary key.

SOS n. See silicon-on-sapphire.

Sound Blaster n. 1. A family of sound cards manufactured by Creative Technology or its subsidiary, Creative Labs. See also sound card. 2. A de facto standard set by the family of sound cards developed by Creative Technologies and its subsidiaries. Many other manufacturers also make Sound Blaster compatible products.

sound board n. See sound card.

sound buffer n. A region of memory used to store the bit image of a sequence of sounds to be sent to a computer s speaker(s).

sound card n. A type of expansion board on PC-compatible computers that allows the playback and recording of sound, such as from a WAV or MIDI file or a music CD-ROM. Most PCs sold at retail include a sound card. Also called: sound board. See also expansion board, MIDI, WAV.

sound clip n. A file that contains a short audio item, usually an excerpt from a longer recording.

sound editor n. A program that allows the user to create and manipulate sound files.

sound generator n. A chip or chip-level circuit that can produce electronic signals that can drive a speaker and synthesize sound.

sound hood n. A five-sided box, lined with soundproofing material, that is placed over a loud printer to muffle its noise.

SoundSentry n. An optional Windows feature that instructs Windows to produce a visual cue such as a screen flash or a blinking title bar whenever a system beep occurs. SoundSentry is designed for users with hearing impairments or users who operate a computer in a noisy environment.

source n. 1. In information processing, a disk, file, document, or other collection of information from which data is taken or moved. Compare destination. 2. In a FET, the electrode toward which charge carriers (electrons or holes) move from the source under control of the gate. See also CMOS (definition 1), drain (definition 1), FET, gate (definition 2), MOSFET, NMOS, PMOS.

source code n. Human-readable program statements written by a programmer or developer in a high-level or assembly language that are not directly readable by a computer. Source code needs to be compiled into object code before it can be executed by a computer. Compare object code.

source code control system n. A tool designed to track changes made to source code files. Changes are documented in such a way that previous versions of the files can be retrieved. Source code control is used in software development, particularly in situations involving concurrent development and multiple user access to source code files.

source computer n. 1. A computer on which a program is compiled. Compare object computer. 2. A computer from which data is transferred to another computer.

source data n. The original data on which a computer application is based.

source data acquisition n. The process of sensing, as with a bar code reader or other scanning device, or receiving source data. See also source data.

source data capture n. See source data acquisition.

source directory n. During a file copy operation, the directory in which the original versions of the files are located.

source disk n. Any disk from which data will be read, as during a copy operation or when an application is loaded from a disk into memory. Compare target disk.

source document n. The original document from which data is taken.

source drive n. The disk drive from which files are being copied during a copy operation.

source file n. 1. A file that contains source code. See also source code. 2. A file that contains the data that a program will process and store in a destination file. 3. In MS-DOS and Windows commands that involve the copying of data or program instructions, the file containing the data or instructions that are copied.

source language n. The programming language in which the source code for a program is written. See also programming language, source code.

source program n. The source code version of a program. See also source code. Compare executable program.

source statement n. A single statement in the source code of a program. See also source code, statement.

SPA n. See SIIA.

spacebar n. The long key occupying much of the bottom row of most keyboards that sends a space character to the computer.

space character n. A character that is entered by pressing the Spacebar on the keyboard and that typically appears on the screen as a blank space.

space-division multiplexing n. The first automated form of communications multiplexing, which replaced the human-operated switchboard. Space-division multiplexing was replaced by frequency-division multiplexing (FDM), which was in turn replaced by time-division multiplexing (TDM). Acronym: SDM. See also FDM, multiplexing, time-division multiplexing.

spaghetti code n. Code that results in convoluted program flow, usually because of excessive or inappropriate use of GOTO or JUMP statements. See also GOTO statement, jump instruction.

spam¹ vb. To distribute unwanted, unrequested mail widely on the Internet by posting a message to too many recipients or too many newsgroups. The act of distributing such mail, known as spamming, angers most Internet users and has been known to invite retaliation, often in the form of return spamming that can flood and possibly disable the electronic mailbox of the original spammer.

spam² n. 1. An unsolicited e-mail message sent to many recipients at one time, or a news article posted simultaneously to many newsgroups. Spam is the electronic equivalent of junk mail. In most cases, the content of a spam message or article is not relevant to the topic of the newsgroup or the interests of the recipient; spam is an abuse of the Internet in order to distribute a message to a huge number of people at minimal cost. 2. An unsolicited e-mail message from a business or individual that seeks to sell the recipient something. Also called: UCE, unsolicited commercial e-mail.

spam blocking n. See address munging.

spambot n. A program or device that automatically posts large amounts of repetitive or otherwise inappropriate material to newsgroups on the Internet. See also bot (definition 3), robopost, spam¹.

spamdexter n. An individual who lures users to spam-related Web sites by loading the site with hundreds of hidden copies of popular keywords, even if those words have no relation to the Web site. Because the keywords appear so many times, the spamdexter s site will appear near the top of search result and indexing lists. The term spamdexter was created by combining the words spam and index. Also called: keyword stuffing.

span n. See range.

SPARC n. Short for Scalable Processor Architecture. A RISC (reduced instruction set computing) microprocessor specification from Sun Microsystems, Inc. See also RISC.

sparse array n. An array (arrangement of items) in which many of the entries are identical, commonly zero. It is not possible to define precisely when an array is sparse, but it is clear that at some point, usually when about one-third of the array consists of identical entries, it becomes worthwhile to redefine the array. See also array.

sparse infector n. A type of virus or other malicious code that delivers its payload only when certain predetermined conditions are met. A sparse infector might hide on an infected computer until a certain date or until a certain number of files or applications have been run. By restricting their active phases to only certain situations, sparse infectors are more likely to avoid detection.

spatial data management n. The representation of data as a collection of objects in space, particularly as icons on a screen, in order to make the data easier to comprehend and manipulate.

spatial digitizer n. A three-dimensional scanner most often used in medical and geographical work. Compare optical scanner.

speaker dependent recognition n. A type of automatic speech recognition (ASR) in which the computer system becomes accustomed to the voice and accent of a specific speaker, allowing a larger vocabulary can be recognized. See also ASR, speaker independent recognition.

speaker independent recognition n. A type of automatic speech recognition (ASR) in which the computer system will respond to commands from any speaker. Because the system does not adjust to the nuances of a specific voice, only a limited vocabulary is possible. See also ASR, speaker dependent recognition.

spec n. See specification.

special character n. Any character that is not alphabetic, numeric, or the space character (for example, a punctuation character). See also reserved character, wildcard character.

special interest group n. See SIG.

special-purpose language n. A programming language whose syntax and semantics are best suited for a given field or approach. See also Prolog.

specification n. 1. A detailed description of something. 2. In relation to computer hardware, an item of information about the computer s components, capabilities, and features. 3. In relation to software, a description of the operating environment and proposed features of a new program. 4. In information processing, a description of the data records, programs, and procedures involved in a particular task. Also called: spec.

spectral color n. In video, the hue represented by a single wavelength in the visible spectrum. See also color model.

spectral response n. In relation to sensing devices, the relationship between the device s sensitivity and the frequency of the detected energy.

spectrum n. The range of frequencies of a particular type of radiation. See also electromagnetic spectrum.

Speech API n. See SAPI.

Speech Application Programming Interface n. See SAPI.

speech recognition n. See voice recognition.

Speech Recognition API n. See SRAPI.

Speech Recognition Application Programming Interface n. See SRAPI.

speech synthesis n. The ability of a computer to produce spoken words. Speech synthesis is produced either by splicing together prerecorded words or by programming the computer to produce the sounds that make up spoken words. See also artificial intelligence, neural network, synthesizer.

spelling checker n. An application that employs a disk-based dictionary to check for misspellings in a document. Also called: spell checker.

spew vb. On the Internet, to post an excessive number of e-mail messages or newsgroup articles.

spider n. An automated program that searches the Internet for new Web documents and indexes their addresses and content-related information in a database, which can be examined for matches by a search engine. Spiders are generally considered to be a type of bot, or Internet robot. Also called: crawler. See also bot (definition 3), search engine (definition 2).

spike n. A transient electrical signal of very short duration and usually high amplitude. Compare surge.

spindle n. 1. An axle for mounting a disk or reel of magnetic tape. 2. Any drive included within the chassis of a laptop or other portable computer. A laptop including a floppy disk drive and a hard drive would be considered a two-spindle machine.

spintronics n. An emerging field of study in electronics and physics that is based on the ability to detect and control the spin of electrons in magnetic materials. Using spintronics, it might eventually be possible to produce small, fast electronic devices, including transistors, memory devices, and quantum computers.

Spirale virus n. See Hybris virus.

splash screen n. A screen containing graphics, animation, or other attention-getting elements that appears while a program is loading or as an introductory page to a Web site. A splash screen used with an application typically contains a logo, version information, author credits, or a copyright notice, and it appears when a user opens a program and disappears when loading is complete. A splash screen used on a Web site serves as a front door, typically loading before any content-related pages.

spline n. In computer graphics, a curve calculated by a mathematical function that connects separate points with a high degree of smoothness. See the illustration. See also B zier curve.

Spline.

split screen n. A display method in which a program can divide the display area into two or more sections, which can contain different files or show different parts of the same file.

spoiler n. A post to a newsgroup or mailing list that reveals what is intended to be a surprise, such as a plot twist in a film or television episode or the solution to a game. The subject line should contain the word spoiler, but netiquette requires that the sender further protect readers who do not or cannot scan posts for subject lines in advance by encrypting the post, putting one or more screenfuls of white space above the text, or both. See also netiquette.

spoofing n. The practice of making a transmission appear to come from an authorized user. For example, in IP spoofing, a transmission is given the IP address of an authorized user in order to obtain access to a computer or network. See also IP address.

spool vb. To store a data document in a queue, where it awaits its turn to be printed. See also print spooler.

spot n. A composite dot produced through the halftone creation process on a PostScript printer that consists of a group of dots arranged in a pattern reflecting the gray level of a particular pixel. See also gray scale, halftone. Compare dot (definition 2).

spot color n. A method of handling color in a document in which a particular color of ink is specified and each page having elements in that color is printed as a separate layer. The printer then prints one layer for each spot color in the document. See also color model, color separation (definition 1), PANTONE MATCHING SYSTEM. Compare process color.

spot function n. The PostScript procedure used to create a given type of screen in a halftone. See also halftone, PostScript, spot.

SPP n. See scalable parallel processing.

spraycan n. An artist s tool in Paintbrush or another graphics application for applying a pattern of dots to an image.

spreadsheet program n. An application commonly used for budgets, forecasting, and other finance-related tasks that organizes data values using cells, where the relationships between cells are defined by formulas. A change to one cell produces changes to related cells. Spreadsheet programs usually provide graphing capabilities for output and a variety of formatting options for text, numeric values, and graph features. See also cell (definition 1).

spread spectrum adj. Of or pertaining to a system of secure radio communication in which the content of a transmission is broken into split-second pieces, which are transmitted over separate frequencies. When a receiver identifies a spread spectrum signal, it reassembles it to its original form. Spread spectrum was invented by the actress Hedy Lamarr in 1940, but it was not used until 1962.

Springboard n. Handspring Inc. s expansion platform for its line of Visor handheld personal digital assistants. The term describes both the 68-pin Springboard socket incorporated into the Visor, as well as a series of add-on Springboard modules that fit into the socket. Add-on modules include features such as multimedia, games, e-books, additional memory storage, and a wireless phone module. See also Visor.

sprite n. In computer graphics, a small image that can be moved on the screen independently of other images in the background. Sprites are widely used in animation sequences and video games. See also object (definition 3).

sprocket feed n. A paper feed in which pins engage holes in the paper to move it through a printer. Pin feed and tractor feed are both sprocket feeds. See also paper feed, pin feed, tractor feed.

SPX n. 1. Acronym for Sequenced Packet Exchange. The transport level (ISO/OSI level 4) protocol used by Novell NetWare. SPX uses IPX to transfer the packets, but SPX ensures that messages are complete. See also ISO/OSI reference model. Compare IPX. 2. Acronym for simplex. See simplex.

SQL n. See structured query language.

square wave n. A blocklike waveform that is generated by a source that changes instantly between alternate states, usually at a single frequency. See the illustration. Compare sine wave.

Square wave.

SRAM n. See static RAM.

SRAPI n. Acronym for Speech Recognition Application Programming Interface. A cross-platform application programming interface for speech recognition and text-to-speech functions supported by a consortium of developers including Novell, IBM, Intel, and Philips Dictation Systems. See also application programming interface, speech recognition.

SSA n. Acronym for Serial Storage Architecture. An interface specification from IBM in which devices are arranged in a ring topology. In SSA, which is compatible with SCSI devices, data can be transferred at up to 20 megabytes per second in each direction. See also SCSI device.

SSD n. Acronym for solid-state disk. See solid-state disk drive.

SSE n. Short for Streaming SIMD Extensions. A set of 70 new instructions implemented in Intel s Pentium III microprocessor. SSE, more formally called Internet SSE (ISSE), uses SIMD (single-instruction, multiple-data) operations to accelerate floating point calculations. Designed to improve performance in visual areas such as real-time 3-D and graphics rendering, SSE also provides support for development of such applications as real-time video and speech recognition. See also SIMD.

SSI n. 1. See small-scale integration. 2. See server-side include.

SSL n. Acronym for Secure Sockets Layer. A protocol developed by Netscape Communications Corporation for ensuring security and privacy in Internet communications. SSL supports authentication of client, server, or both, as well as encryption during a communications session. While primary purpose of SSL is to enable secure electronic financial transactions on the World Wide Web, it is designed to work with other Internet services as well. This technology, which uses public key encryption, is incorporated into the Netscape Navigator Web browser and Netscape s commerce servers. See also commerce server, open standard, public key encryption, PCT. Compare S-HTTP.

SSO n. See single sign-on.

ST506 interface n. The hardware signal specification developed by Seagate Technologies for hard-disk-drive controllers and connectors. The ST506/412 version of this interface has become a de facto standard.

stack n. A region of reserved memory in which programs store status data such as procedure and function call addresses, passed parameters, and sometimes local variables. See also pop, push (definition 1). Compare heap (definition 1).

stacking order n. The order in which layers in a digital graphic file are arranged. Foreground elements are typically stacked on top of background elements. Changes in stacking order can affect the way the final graphic is seen by the viewer. See also layering.

stack pointer n. A register that contains the current address of the top element of the stack. See also pointer (definition 1), stack.

stackware n. A HyperCard application consisting of a HyperCard data stack and HyperCard programming. See also HyperCard.

staging web n. A local Web site maintained on a file system or local Web server that currently cannot be browsed by site visitors. These Web sites allow authors and workgroups to make changes or updates to Web sites before they are published.

staging Web server n. A Web server where you publish and test your Web site before putting it on a production server. A staging Web server cannot be browsed by an Internet or intranet audience.

stairstepping n. A rough outline like the steps of a stair in a graphic line or curve that should be smooth. Also called: aliasing, jaggies.

stale link n. A hyperlink to an HTML document that has been deleted or moved, rendering the hyperlink useless. See also HTML document, hyperlink.

stale pointer bug n. See aliasing bug.

stand-alone or standalone adj. Of, pertaining to, or being a device that does not require support from another device or system, for example, a computer that is not connected to a network.

standard n. 1. A de jure technical guideline advocated by a recognized noncommercial or government organization that is used to establish uniformity in an area of hardware or software development. The standard is the result of a formal process, based on specifications drafted by a cooperative group or committee after an intensive study of existing methods, approaches, and technological trends and developments. The proposed standard is later ratified or approved by a recognized organization and adopted over time by consensus as products based on the standard become increasingly prevalent in the market. Standards of this type are numerous, including the ASCII character set, the RS-232-C standard, the SCSI interface, and ANSI-standard programming languages, such as C and FORTRAN. See also ANSI, convention, RS-232-C standard, SCSI. 2. A de facto technical guideline for hardware or software development that occurs when a product or philosophy is developed by a single company and, through success and imitation, becomes so widely used that deviation from the norm causes compatibility problems or limits marketability. This type of highly informal standard setting is exemplified by Hayes-compatible modems and IBM PC compatible computers. See also compatibility (definition 3).

standard ASCII n. The set of characters assigned to ASCII (American Standard Code for Information Interchange) values between decimal 0 and 127 (hexadecimal 00 through 7F). These characters include most found on a standard keyboard, including the letters A Z (uppercase and lowercase), numerals (0 through 9), and some special characters, such as colons and parentheses. Standard ASCII has for years been used as a near-universal common language in the PC environment for enabling different programs to exchange information reliably. See also ASCII. Compare Extended ASCII.

standard deviation n. In statistics, a measure of the dispersion of a group of measurements relative to the mean (average) of that group. Each score s difference from the mean is squared, and the standard deviation is defined as the square root of the average of these squared values.

standard disclaimer n. A phrase placed in an e-mail message or news article that is intended to replace the statement required by some businesses and institutions that the contents of the message or article do not necessarily represent the opinions or policies of the organization from whose e-mail system the message originated.

standard function n. A function that is always available within a particular programming language. See also function (definition 1).

Standard Generalized Markup Language n. See SGML.

standby n. A state in which your computer consumes less power when it is idle but remains available for immediate use. While your computer is on standby, information in computer memory is not saved on your hard disk. If there is an interruption in power, the information in memory is lost.

star n. See *.

star bus n. A network topology in which nodes connect to hubs in a star pattern, but the hubs are connected by a bus trunk. Star bus is a combination of star and bus topologies.

star-dot-star or star dot star n. A file specification (*.*) using the asterisk wildcard, which means any combination of file name and extension in operating systems such as MS-DOS. See also *.*, asterisk, wildcard character.

star network n. A LAN (local area network) in which each device (node) is connected to a central computer in a star-shaped configuration (topology); commonly, a network consisting of a central computer (the hub) surrounded by terminals. See the illustration. Compare bus network, ring network.

Star network.

start bit n. In asynchronous transmission, the bit (actually, a timing signal) that represents the beginning of a character. See also asynchronous transmission. Compare parity bit, stop bit.

Start button n. In Microsoft Windows 9x and Windows NT 4 and later, the control on the desktop task bar that opens the main menu.

starting point n. A World Wide Web document designed to help users begin navigating the Web. A starting point often contains tools such as search engines and hyperlinks to selected Web sites. See also hyperlink, search engine (definition 2), World Wide Web.

star topology n. A network configuration based on a central hub, from which nodes radiate in a star-shaped pattern. See also topology.

start page n. See home page (definition 2).

start/stop transmission n. See asynchronous transmission.

startup n. See boot¹.

startup application n. On the Macintosh, the application that takes control of the system when the computer is turned on.

STARTUP.CMD n. A special-purpose batch file stored in the root directory of the startup disk in OS/2 the OS/2 equivalent of an MS-DOS AUTOEXEC.BAT file.

startup disk n. See system disk.

startup ROM n. The bootstrap instructions coded into a computer s ROM (read-only memory) and executed at startup. The startup ROM routines enable a computer to check itself and its devices (such as the keyboard and disk drives), prepare itself for operation, and run a short program to load an operating-system loader program. See also boot¹, power-on self test.

startup screen n. A text or graphics display that appears on the screen when a program is started (run). Startup screens usually contain information about the software s version and often contain a product or corporate logo.

star-wired ring n. A network topology in which hubs and nodes connect to a central hub in typical star fashion, but the connections within the central hub form a ring. Star-wired ring is a combination of star and ring topologies.

state n. See status.

stateful adj. Of or pertaining to a system or process that monitors all details of the state of an activity in which it participates. For example, stateful handling of messages takes account of their content. Compare stateless.

stateless adj. Of or pertaining to a system or process that participates in an activity without monitoring all details of its state. For example, stateless handling of messages might take account of only their sources and destinations but not their content. Compare stateful.

statement n. The smallest executable entity within a programming language.

state-of-the-art adj. Up to date; at the forefront of current hardware or software technology.

static¹ adj. In information processing, fixed or predetermined. For example, a static memory buffer remains invariant in size throughout program execution. The opposite condition is dynamic, or ever-changing.

static² n. In communications, a crackling noise caused by electrical interference with a transmitted signal. See also noise (definition 2).

static allocation n. Apportionment of memory that occurs once, usually when the program starts. The memory remains allocated during the program s execution and is not deallocated until the program is finished. See also allocate, deallocate. Compare dynamic allocation.

static binding n. Binding (converting symbolic addresses in the program to storage-related addresses) that occurs during program compilation or linkage. Also called: early binding. Compare dynamic binding.

static buffer n. A secondary sound buffer that contains an entire sound; these buffers are convenient because the entire sound can be written once to the buffer. See also streaming buffer.

static electricity n. An electrical charge accumulated in an object. Although generally harmless to humans, the discharge of static electricity through an electronic circuit can cause severe damage to the circuit.

static RAM n. A form of semiconductor memory (RAM) based on the logic circuit known as a flip-flop, which retains information as long as there is enough power to run the device. Static RAMs are usually reserved for use in caches. Acronym: SRAM. See also cache, RAM, synchronous burst static RAM. Compare dynamic RAM.

static routing n. Routing based on a fixed forwarding path. Unlike dynamic routing, static routing does not adjust to changing network conditions. Compare dynamic routing.

static Web page n. Web page that displays the same content to all viewers. Usually written in hypertext markup language (HTML), a static Web page displays content that changes only if the HTML code is altered. See also dynamic Web page.

station n. 1. In the IEEE 802.11 wireless LAN specification, a single, often mobile, node. 2. See workstation.

stationery¹ adj. Describing a type of document that, when opened by the user, is duplicated by the system; the copy is opened for the user s modification while the original document remains intact. Stationery documents can be used as document templates or boilerplates. See also boilerplate, template (definition 5).

stationery² n. A stationery document. See also stationery¹.

statistical multiplexer n. A multiplexing device that adds intelligence to time-division multiplexing by using buffering (temporary storage) and a microprocessor to combine transmission streams into a single signal and to allocate available bandwidth dynamically. Also called: stat mux. See also dynamic allocation, multiplexing, time-division multiplexing.

statistics n. The branch of mathematics that deals with the relationships among groups of measurements and with the relevance of similarities and differences in those relationships. See also binomial distribution, Monte Carlo method, probability, regression analysis, standard deviation, stochastic.

stat mux n. See statistical multiplexer.

status n. The condition at a particular time of any of numerous elements of computing a device, a communications channel, a network station, a program, a bit, or other element used to report on or to control computer operations.

status bar n. In Windows 9x and Windows NT 4 and later, a space at the bottom of many program windows that contains a short text message about the current condition of the program. Some programs also display an explanation of the currently selected menu command in the status bar. See the illustration.

Status bar.

status codes n. Strings of digits or other characters that indicate the success or failure of some attempted action. Status codes were commonly used to report the results of early computer programs, but most software today uses words or graphics. Internet users, especially those with UNIX shell accounts, are likely to encounter status codes while using the Web or FTP. See also HTTP status codes.

steganography n. A hide-in-plain-sight technique for concealing information by embedding a message within an innocuous cover message. In steganography, bits of unnecessary data within an image, sound, text, or even a blank file are replaced with bits of invisible information. The term steganography comes from the Greek for covered writing and has traditionally included any method of secret communication that conceals the existence of the message. Because steganography cannot be detected by decryption software, it is often used to replace or supplement encryption.

step-frame n. The process of capturing video images one frame at a time. This process is used by computers that are too slow to capture analog video images in real time.

stepper motor n. A mechanical device that rotates only a fixed distance each time it receives an electrical pulse. A stepper motor is part of a disk drive.

step-rate time n. The time required to move a disk actuator arm from one track to the next. See also actuator, stepper motor.

stereogram n. See autostereogram.

sticky adj. In reference to a Web site, properties such as targeted content or services that increase the amount of time users choose to spend at the site and increase user s desire to return to the site repeatedly.

StickyKeys n. An accessibility feature built into Macintosh and Windows computers that causes modifier keys such as Shift, Control, or Alt to stay on after they are pressed, eliminating the need to press multiple keys simultaneously. This feature facilitates the use of modifier keys by users who are unable to hold down one key while pressing another.

stochastic adj. Based on random occurrences. For example, a stochastic model describes a system by taking into account chance events as well as planned events.

stop bit n. In asynchronous transmission, a bit that signals the end of a character. In early electromechanical teleprinters, the stop bit provided time for the receiving mechanism to coast back to the idle position and, depending on the mechanism, had a duration of 1, 1.5, or 2 data bits. See also asynchronous transmission. Compare parity bit, start bit.

Stop error n. A serious error that affects the operating system and that could place data at risk. The operating system generates an obvious message, a screen with the Stop error, rather than continuing on and possibly corrupting data. Also called: blue screen error, fatal system error. See also Blue Screen of Death.

storage n. In computing, any device in or on which information can be kept. Microcomputers have two main types of storage: random access memory (RAM) and disk drives and other external storage media. Other types of storage include read-only memory (ROM) and buffers.

storage area network n. A high-speed network that provides a direct connection between servers and storage, including shared storage, clusters, and disaster-recovery devices. A storage area network, or SAN, includes components such as hubs and routers that are also used in local area networks (LANs), but it differs in being something of a subnetwork dedicated to providing a high-speed connection between storage elements and servers. Most SANs rely on fiber-channel connections that deliver speeds up to 1000 Mbps and can support up to 128 devices. SANs are implemented to provide the scalability, speed, and manageability required in environments that demand high data availability. Acronym: SAN. Also called: system area network.

storage device n. An apparatus for recording computer data in permanent or semipermanent form. When a distinction is made between primary (main) storage devices and secondary (auxiliary) storage devices, the former refers to random access memory (RAM) and the latter refers to disk drives and other external devices.

storage location n. The position at which a particular item can be found either an addressed location or a uniquely identified location on a disk, tape, or similar medium.

storage media n. The various types of physical material on which data bits are written and stored, such as floppy disks, hard disks, tape, and optical discs.

storage tube n. See direct view storage tube.

store-and-forward n. A method of delivering transmissions in which messages are held temporarily by an intermediary before being sent on to their destination. Store and forward is used by some switches in delivering packets to their destinations. Compare cut-through switch.

stored procedure n. A precompiled collection of SQL statements and optional control-of-flow statements stored under a name and processed as a unit. They are stored in an SQL database and can be run with one call from an application.

stored program concept n. A system architecture scheme, credited largely to the mathematician John von Neumann, in which both programs and data are in direct-access storage (random access memory, or RAM), thereby allowing code and data to be treated interchangeably. See also von Neumann architecture.

storefront n. See virtual storefront.

storm n. On a network, a sudden, excessive burst of traffic. Storms are often responsible for network outages.

STP n. Acronym for shielded twisted pair. A cable consisting of one or more twisted pairs of wires and a sheath of foil and copper braid. The twists protect the pairs from interference by each other, and the shielding protects the pairs from interference from outside. Therefore, STP cable can be used for high-speed transmission over long distances. See also twisted-pair cable. Compare UTP.

straight-line code n. Program code that follows a direct sequence of statements rather than skipping ahead or jumping back via transfer statements such as GOTO and JUMP. See also GOTO statement, jump instruction. Compare spaghetti code.

stream¹ n. Any data transmission, such as the movement of a file between disk and memory, that occurs in a continuous flow. Manipulating a data stream is a programming task. Consumers, however, are likely to encounter references to streams and streaming in connection to the Internet, which has increased reliance on stream techniques to enable users (even those with slower equipment) to access large multimedia files especially those containing audio and video components and to display or play them before all the data has been transferred.

stream² vb. To transfer data continuously, beginning to end, in a steady flow. Many aspects of computing rely on the ability to stream data: file input and output, for example, and communications. If necessary, an application receiving a stream must be able to save the information to a buffer in order to prevent loss of data. On the Internet, streaming enables users to begin accessing and using a file before it has been transmitted in its entirety.

stream cipher n. A method for encrypting a data sequence of unlimited length using a key of fixed length. See also key (definition 3). Compare block cipher.

streaming n. 1. On the Internet, the process of delivering information, especially multimedia sound or video, in a steady flow that the recipient can access as the file is being transmitted. 2. In magnetic tape storage devices, a low-cost technique to control the motion of the tape by removing tape buffers. Although streaming tape compromises start/stop performance, it achieves highly reliable storage and retrieval of data, and is useful when a steady supply of data is required by a particular application or computer.

streaming buffer n. A small sound buffer that can play lengthy sounds because the application dynamically loads audio data into the buffer as it plays. For example, an application could use a buffer that can hold 3 seconds of audio data to play a 2-minute sound. A streaming buffer requires much less memory than a static buffer. See also static buffer.

Streaming Server n. A server technology designed by Apple Computer to send streaming QuickTime media files over the Internet. Built on RTP and RTSP standard Internet protocols, Streaming Server can set up a QuickTime streaming media Web broadcasting station capable of streaming digital videos and music files to more than 3000 users via the Internet. Streaming Server may be used with Mac OS X and other UNIX-based operating systems. Also called: Darwin Streaming Server, QuickTime Streaming Server.

streaming tape n. See tape (definition 1).

stream interface device driver n. A user-level DLL that controls devices connected to a Windows CE based platform. A stream interface device driver presents the services of a hardware device to applications by exposing Win32 stream interface functions. Stream interface drivers also can control devices built into a Windows CE based platform, depending on the software architecture for the drivers. Also called: installable device driver.

stream-oriented file n. A file used to store a fairly continuous series of bits, bytes, or other small, structurally uniform units.

street price n. The actual retail or mail-order price of a consumer hardware or software product. In most cases, the street price is somewhat lower than the suggested retail price.

stress test n. A test of a software or hardware system s functional limits, performed by subjecting the system to extreme conditions, such as peak volumes of data or extremes in temperature.

strikethrough n. One or more lines drawn through a selected range of text, usually to show deletion or the intent to delete. See the illustration.

Strikethrough.

string n. A data structure composed of a sequence of characters usually representing human-readable text.

string variable n. An arbitrary name assigned by the programmer to a string of alphanumeric characters and used to reference that entire string. See also string.

stripe vb. See disk striping.

stripe pitch n. The distance, measured horizontally, between bands of phosphor that are the same color on a cathode ray tube (CRT) display based on aperture grill technology. Although the measurements are based on different methods of applying phosphor to the screen surface, stripe pitch is comparable to dot pitch, the measurement used with CRTs based on shadow mask technology. See also aperture grill, CRT, mask (definition 2). Compare dot pitch, slot pitch.

striping n. A means of protecting data on a network by spreading it across multiple disks. In the most commonly used approach, striping is combined with parity (error-correcting information) to ensure that if some portion of the data is lost, it can be reconstructed. Striping is implemented in RAID security. See also RAID. Compare disk mirroring.

strobe n. A timing signal that initiates and coordinates the passage of data, typically through an input/output (I/O) device interface, such as a keyboard or printer.

stroke n. 1. In data entry, a keystroke a signal to the computer that a key has been pressed. 2. In typography, a line representing part of a letter. 3. In paint programs, a swipe of the brush made with the mouse or keyboard in creating a graphic. 4. In display technology, a line created as a vector (a path between two coordinates) on a vector graphics display (as opposed to a line of pixels drawn dot by dot on a raster graphics display).

stroke font n. A font printed by drawing a combination of lines rather than by filling a shape, as with an outline font. Compare outline font.

stroke weight n. The width, or thickness, of the lines (strokes) that make up a character. See also font.

stroke writer n. In video, a display unit that draws characters and graphic images as sets of strokes lines or curves connecting points rather than as sets of dots, as on a typical raster-scan monitor. See also vector graphics.

StrongARM n. The architecture underlying Intel s low-power, high-performance SA microprocessors. StrongARM is based on the 32-bit RISC architecture licensed by ARM Limited. StrongARM-based SA microprocessors support a number of platforms, including Windows CE and Java, and are designed for use in four primary areas: smart portable devices, such as cellular phones and handheld computers; Internet access devices, such as set-top boxes; networking devices, such as switches and routers; and embedded controls, such as entertainment devices and automation equipment. See also ARM.

strong name n. A name that consists of an assembly s identity: its simple text name, version number, and often the culture information strengthened by a public key and a digital signature generated over the assembly. Assemblies with the same strong name are expected to be identical.

strong typing n. A characteristic of a programming language that does not allow the program to change the data type of a variable during program execution. See also data type, variable. Compare weak typing.

structure n. 1. The design and composition of a program, including program flow, hierarchy, and modularity. 2. A collection of data elements. See also data structure.

structured graphics n. See object-oriented graphics.

structured programming n. Programming that produces programs with clean flow, clear design, and a degree of modularity or hierarchical structure. See also modular programming, object-oriented programming. Compare spaghetti code.

structured query language n. A database sublanguage used in querying, updating, and managing relational databases the de facto standard for database products. Acronym: SQL.

structured walkthrough n. 1. A meeting of programmers working on different aspects of a software development project, in which the programmers attempt to coordinate the various segments of the overall project. The goals, requirements, and components of the project are systematically reviewed in order to minimize the error rate of the software under development. 2. A method for examining a computer system, including its design and implementation, in a systematic fashion.

STT n. See Secure Transaction Technology.

stub n. A routine that contains no executable code and that generally consists of comments describing what will eventually be there; it is used as a placeholder for a routine to be written later. Also called: dummy routine. See also top-down programming.

StuffIt n. A file compression program originally written for the Apple Macintosh, used for storing a file on one or more disks. Originally shareware, StuffIt is now a commercial product for Macs and PCs that supports multiple compression techniques and allows file viewing. StuffIt files can be uncompressed using a freeware program, StuffIt Expander.

style sheet n. 1. A file of instructions used to apply character, paragraph, and page layout formats in word processing and desktop publishing. 2. A text file containing code to apply semantics such as page layout specifications to an HTML document. See also HTML document, semantics (definition 1).

stylus n. A pointing device, similar to a pen, used to make selections, usually by tapping, and to enter information on the touch-sensitive surface.

subclass n. A class in object-oriented programming that is derived from, and inherits its attributes and methods from, another class known as a superclass. Compare superclass.

subcommand n. A command in a submenu (a menu that appears when a user selects an option in a higher-level menu).

subdirectory n. A directory (logical grouping of related files) within another directory.

subdomain n. A domain, often representing an administrative or other organizational subgroup within a second-level domain. See also domain.

subform n. A form contained within another form or a report.

subject drift n. See topic drift.

subject tree n. A type of World Wide Web index that is organized by subject categories, many of which are broken down into subcategories, or branches. An example of a World Wide Web subject tree is Yahoo! See also Yahoo!.

submarining n. A phenomenon that occurs when some part of a screen display moves more quickly than the screen can show. The object (such as the mouse pointer) disappears from the screen and reappears where it comes to rest, just as a submarine resurfaces after a dive. Submarining is especially a problem with the slowly responding passive-matrix LCD displays on many laptop computers.

submenu n. A menu that appears as the result of the selection of an item on another, higher-level menu.

subnet n. 1. In general, a network that forms part of a larger network. 2. In terms of the ISO/OSI reference model, the subnet comprises the layers below the transport layer that is, the network, data link, and physical layers.

subnet mask n. See address mask.

subnetting n. The division of a network into subnets to improve network security and performance. See also subnet (definition 1). Compare supernetting.

subnetwork n. A network that is part of another, larger network.

subnotebook n. A class of portable computer that is smaller in size and lighter in weight than a full-sized laptop. Subnotebooks feature a reduced-sized keyboard and screen and often use an external floppy drive to save space and weight. Despite their size, subnotebooks retain all the functions of a full-sized portable computer.

subportable n. See subnotebook.

subprogram n. A term used in some languages for routine (procedure or function) because the structure and syntax of a subprogram closely model those of a program. See also program, routine.

subreport n. A report contained within another report.

subroutine n. A common term for routine, likely to be used in reference to shorter, general, frequently called routines. See also procedure, routine.

subschema n. The definition of a user view of the database (in CODASYL/DBTG systems only), roughly equivalent to the external schema of an ANSI/X3/SPARC database management system or to a view in a relational database management system. See also schema.

subscribe vb. 1. To add a newsgroup to the list of such groups from which a user receives all new articles. 2. To add a name to a LISTSERV distribution list. See also LISTSERV.

Subscriber Identity Module card n. See SIM card.

subscript n. 1. One or more characters printed slightly below the baseline of surrounding text. See also baseline. Compare superscript. 2. In programming, one or more numbers or variables that identify the location of an element in an array. See also array, index (definition 2).

subscription site n. E-commerce Web site that provides information or services to customers who pay a subscription fee.

substrate n. The inactive supporting material used in a manufacturing process. In circuit boards, it is the base to which the traces (foil areas) are attached. In tapes and disks, it is the material on which the magnetic particles are fused.

substring n. A sequential section of a string. See also string.

subtransaction n. See nested transaction.

subtree n. Any node within a tree, along with any selection of connected descendant nodes. See also node (definition 3), tree.

subweb n. A named subdirectory of the root Web site that is a complete FrontPage-based Web site. Each subweb can have independent administration, authoring, and browsing permissions from the root Web site and other subwebs.

suitcase n. A file on Macintosh computers that contains one or more fonts or desk accessories. In early versions of the operating system, such files are indicated with the icon of a suitcase. See also font suitcase.

suite n. 1. A set of application programs sold as a package, usually at a lower price than that of the individual applications sold separately. A suite for office work, for example, might contain a word processing program, a spreadsheet, a database management program, and a communications program. 2. See protocol suite.

summarize vb. To post the results of a survey or vote in short form to a newsgroup or mailing list after collecting the results by e-mail.

SunOS n. Short for Sun Operating System. A variety of the UNIX operating system used on workstations from Sun Microsystems, Inc.

superclass n. A class in object-oriented programming from which another class a subclass is derived. The subclass inherits its attributes and methods from the superclass. Compare subclass.

supercomputer n. A large, extremely fast, and expensive computer used for complex or sophisticated calculations. See also computer.

superconductor n. A substance that has no resistance to the flow of electricity.

SuperDrive n. An Apple 3.5-inch disk drive that can read and write in both Apple Macintosh (400K and 800K) and MS-DOS/Windows (720K and 1.44-MB) formats.

super-large-scale integration n. A reference to the density with which components (transistors and other elements) are packed onto an integrated circuit and to the fineness of the connections between them. The actual number of components is nonspecific, but generally considered to be in of 50,000 to 100,000 range. Acronym: SLSI. See also integrated circuit. Compare large-scale integration, medium-scale integration, small-scale integration, ultra-large-scale integration, very-large-scale integration.

superminicomputer n. See computer.

supernetting n. The aggregation of multiple network addresses of the same class into a single block. See also classless interdomain routing, IP address classes. Compare subnetting.

superpipelining n. A method of preprocessing used by some microprocessors in which two or more of a microprocessor s execution stages (fetch, decode, execute, and write-back) are divided into two or more pipelined stages, resulting in higher performance. See also DECchip 21064, pipelining (definition 1).

superscalar adj. Of, pertaining to, or being a microprocessor architecture that enables the microprocessor to execute multiple instructions per clock cycle. See also CISC, RISC.

superscript n. A character printed slightly above the surrounding text, usually in smaller type. Compare subscript (definition 1).

superserver n. A network server with especially high capabilities for speed and data storage. See also server (definition 1).

superstitial n. An Internet ad format that downloads in the background while a user is viewing a Web page and then plays in a pop-up window when triggered by a mouse click or a break in surfing. Because the superstitial doesn t appear until it has completely downloaded and temporarily cached itself on the user s system, attention-getting effects like animation, sound, and large graphics can be used without slowing down the ad. Unicast developed the polite cache and play technology used with the superstitial ad format.

supertwist display n. A form of passive-matrix liquid crystal displays (LCDs) that rotates polarized light as it passes through liquid crystal molecules in which the top and bottom orientations of the molecules causes them to twist 180 to 270 degrees. This technology is used to improve contrast and widen the screen s viewing angle. Supertwist displays, also known as supertwist nematic displays, are widely used and are less expensive than active-matrix displays. Different forms of supertwist displays include DSTN (double supertwist nematic), which is based on two supertwist layers with opposite twist directions, and CSTN (color supertwist nematic), which produces wide-angle, high-quality color. Nematic refers to microscopic threadlike bodies characteristic of the liquid crystals used in these displays. Supertwist displays are widely used in cellular telephones and other devices that may be used in low-light environments. Also called: color supertwist nematic display, CSTN, double supertwist nematic, DSTN, twisted nematic display. See also twisted nematic display.

superuser n. A UNIX user account with root (i.e., unrestricted) access privileges, usually that of a system administrator. See also root account, system administrator, user account.

super VAR n. Short for super value-added reseller. A large value-added reseller. See also value-added reseller.

Super VGA n. See SVGA.

supervisor n. 1. See operating system. 2. A metaoperating system under which several operating systems are active. See also metaoperating system.

supervisor state n. The most privileged of the modes in which a Motorola 680x0 microprocessor can operate. Every operation of which the microprocessor is capable can be executed in the supervisor state. See also privileged mode. Compare user state.

support¹ n. Assistance, such as technical advice provided to customers.

support² vb. To work with another program or product; for example, an application might support file transfers from another program.

surf vb. To browse among collections of information on the Internet, in newsgroups, in Gopherspace, and especially on the World Wide Web. As in channel surfing while watching television, users ride the wave of what interests them, jumping from topic to topic or from one Internet site to another. Also called: cruise.

surface modeling n. A display method used by some CAD programs that gives on-screen constructions the appearance of solidity. See also CAD. Compare solid model, wire-frame model.

surface-mount technology n. A method of manufacturing printed circuit boards in which chips are fixed directly to the surface of the board instead of being soldered into holes predrilled to hold them. Its advantages are compactness, resistance to vibration, and the capacity for dense interconnections on both sides of the board. Acronym: SMT. Compare DIP, leadless chip carrier, pin grid array.

surge n. A sudden and possibly damaging increase in line voltage. See also surge protector, voltage regulator. Compare power failure, spike.

surge protector n. A device that prevents surges from reaching a computer or other kinds of electronic equipment. Also called: surge suppressor. See also surge, transient suppressor.

surge suppressor n. See surge protector.

suspend vb. To halt a process temporarily. See also sleep.

Suspend command n. A power management feature of Windows 9x and Windows NT 4 and later for portable computers. Clicking on the Suspend command in the Start menu allows the user to temporarily suspend operations of the machine (enter Suspend mode ) without turning the power off, saving battery power without having to restart applications or reload data.

suspend mode n. See sleep mode.

sustained transfer rate n. A measure of the speed at which data can be transferred to a storage device such as a disk or a tape. The sustained transfer rate is the data transfer speed that can be kept up by the device for an extended period of time.

SVC n. Acronym for switched virtual circuit. A logical connection between two nodes on a packet-switching network that is established only when data is to be transmitted. See also node (definition 1), packet switching. Compare PVC.

SVG n. Acronym for Scalable Vector Graphics. An XML-based language for device-independent description of two-dimensional graphics. SVG images maintain their appearance when printed or when viewed with different screen sizes and resolutions. SVG is a recommendation of the World Wide Web Consortium (W3C).

SVGA n. Acronym for Super Video Graphics Array. A video standard established by the Video Electronics Standards Association (VESA) in 1989 to provide high-resolution color display on IBM-compatible computers. Although SVGA is a standard, compatibility problems can occur with the video BIOS. See also BIOS, video adapter.

S-video connector n. A hardware interface for video devices that handles chrominance (color) and luminance (black and white) separately. An S-video connector is capable of providing a sharper image than those achieved with systems using RCA-type, or composite, connectors.

S/WAN n. See secure wide area network.

swap vb. 1. To exchange one item for another, as in swapping floppy disks in and out of a single drive. 2. To move segments of programs or data between memory and disk storage. See also virtual memory.

swap file n. A hidden file on the hard drive that Windows uses to hold parts of programs and data files that do not fit in memory. The operating system moves data from the swap file to memory as needed and moves data out of memory to the swap file to make room for new data. The swap file is a form of virtual memory. See also memory, virtual memory.

swap-on-the-fly n. In Linux, a process which allows swap space to be added as needed. Swap-on-the-fly allows a swap file to be created at any time on any available disk, and active only until the system is shut down.

swapping n. 1. A technique for enabling an operating system, and therefore a computer, to address roughly, have available more memory than is physically present in the system. Swapping in this sense (as opposed to swapping disks in and out of a drive, for example) involves moving blocks of information in units known as pages between memory and disk as they are needed during the execution of the application. Swapping is supported by operating systems such as Windows NT and later, Windows 9x and later, OS/2, and Linux. 2. A technique for moving entire processes in and out of main memory. 3. In programming, the process of exchanging two values for example, exchanging values between two variables. See also page (definition 2), swap, swap file, virtual memory.

swap space n. See swap file.

swarm intelligence n. An emerging subfield of artificial intelligence that relies on the collective knowledge of relatively simple particles or agents. Based loosely on the principles of social insect colonies, it seeks to apply the collective intelligence of fragmented agents or groups. It emphasizes distributedness, direct or indirect interactions, flexibility, and robustness. Successful applications of its principles have been evidenced in communications networks, and robotics. See also artificial intelligence, robotics.

Swatch n. Short for Simple Watcher. A UNIX log monitoring and alarm program. Swatch filters system log data as specified by the user, forwarding only important data. Swatch also looks for patterns of changes made in the log file and alerts the user to system problems as they occur.

swim n. A condition in which images slowly move about the positions they are supposed to occupy on screen.

SWING set n. A library of Java GUIs that run uniformly on any native platform that supports the Java Virtual Machine (JVM). Swing Set components have largely supplanted Sun Microsystems s Abstract Window Toolkit. See also Abstract Window Toolkit, graphical user interface, Java Virtual Machine.

switch n. 1. A circuit element that has two states: on and off. 2. A control device that allows the user to choose one of two or more possible states. 3. In communications, a computer or electromechanical device that controls routing and operation of a signal path. 4. In networking, a device capable of forwarding packets directly to the ports associated with particular network addresses. See also bridge, multilayer, router. 5. In operating systems such as MS-DOS, an argument used to control the execution of a command or an application, typically starting with a slash character (/).

switch box n. An enclosure that contains a selector switch. When a user selects a switch setting, the signal passing through the box may be directed either from a single input to one of multiple outputs, or from the selected input to a single output. Switch boxes are often used to connect multiple peripherals, such as printers, to a single port.

switched configuration n. A communications link in which a signal moves from the origin to a switch that routes the signal to one of several possible destinations. Compare point-to-point configuration.

switched Ethernet n. An Ethernet network run through a high-speed switch instead of an Ethernet hub. A switched Ethernet involves dedicated bandwidth of 10 Mbps between stations rather than a shared medium. See also Ethernet (definition 1), switch (definition 3).

switched line n. A standard dial-up telephone connection; the type of line established when a call is routed through a switching station. Compare leased line.

Switched Multimegabit Data Services n. See SMDS.

switched network n. A communications network that uses switching to establish a connection between parties, such as the dial-up telephone system.

Switched T1 n. A circuit-switched form of T1 communications. See also T1.

switched virtual circuit n. See SVC.

Switcher n. A special Macintosh utility that allowed more than one program to be resident in memory at one time. Switcher was made obsolete by MultiFinder. See also MultiFinder.

switching n. A communications method that uses temporary rather than permanent connections to establish a link or to route information between two parties. In the dial-up telephone network, for example, a caller s line goes to a switching center, where the actual connection is made to the called party. In computer networks, message switching and packet switching allow any two parties to exchange information. In both instances, messages are routed (switched) through intermediary stations that together serve to connect the sender and the receiver.

switching hub n. A central device (switch) that connects separate communication lines in a network and routes messages and packets among the computers on the network. The switch functions as a hub, or PBX, for the network. See also hub, packet (definition 1), PBX, switch (definition 3), switched Ethernet, switched network.

switching speed n. In a packet-switching telecommunications technology, such as ATM, the speed at which data packets are sent through the network. Switching speed is generally measured in kilobits or megabits per second. See also ATM (definition 1), packet switching.

SYLK file n. Short for symbolic linkfile. A file constructed with a proprietary Microsoft format, used primarily for exchanging spreadsheet data in such a way that formatting information and intercellular data value relationships are preserved.

symbol n. In programming, a name that represents a register, an absolute value, or a memory address (relative or absolute). See also identifier, operator (definition 1).

symbol font n. A special font or typeface that replaces the characters normally accessible from the keyboard with alternative characters used as symbols, such as scientific, linguistic, or foreign-alphabet characters.

symbolic address n. A memory address that can be referred to in a program by name rather than by number.

symbolic coding n. The expression of an algorithm in words, decimal numbers, and symbols rather than in binary numbers, so that a person can read and understand it. Symbolic coding is used in high-level programming languages. See also algorithm, high-level language.

symbolic language n. A computer language that uses symbols such as keywords, variables, and operators to form instructions. All computer languages except machine language are symbolic.

symbolic link n. A disk directory entry that takes the place of a directory entry for a file but is actually a reference to a file in a different directory. Also called: alias, shortcut, soft link, symlink.

symbolic logic n. A representation of the laws of reasoning, so named because symbols rather than natural-language expressions are used to state propositions and relationships. See also logic.

symbol set n. Any collection of symbols legitimized by a data-coding system, such as extended ASCII, or a programming language.

symbol table n. A list of all identifiers encountered when a program is compiled (or assembled), their locations in the program, and their attributes, such as variable, routine, and so on. See also compile, identifier, linker, module (definition 1), object code.

symlink n. See symbolic link.

symmetric digital subscriber line n. See SDSL.

symmetric multiprocessing n. See SMP.

symmetric multiprocessing server n. See SMP server.

SYN n. Short for synchronous idle character. A character used in synchronous (timed) communications that enables the sending and receiving devices to maintain the same timing. Also called: sync character.

sync character n. See SYN.

syncDRAM n. See SDRAM.

synchronization n. 1. In networking, a communications transmission in which multibyte packets of data are sent and received at a fixed rate. See also packet (definition 1). 2. In networking, the matching of timing between computers on the network. All of the computers are generally assigned identical times to facilitate and coordinate communications. 3. In a computer, the matching of timing between components of the computer so that all are coordinated. For instance, operations performed by the operating system are generally synchronized with the signals of the machine s internal clock. See also clock (definition 1), operating system. 4. In application or database files, version comparisons of copies of the files to ensure they contain the same data. 5. In multimedia, precise real-time processing. Audio and video are transmitted over a network in synchronization so that they can be played back together without delayed responses. See also real-time. 6. In handheld computing, the process of updating or backing up the data on a handheld computer to the linked software applications on a desktop computer. Data changes made on the desktop computer may also be copied to the handheld during synchronization. See also partnership.

synchronization signal n. See sync signal.

synchronize vb. To cause to occur at the same time.

Synchronized Multimedia Integration Language n. See SMIL.

synchronous adj. Occurring at the same time. In computer transmissions, a reference to activity governed by a clock or by synchronized timing.

synchronous burst static RAM n. A type of static RAM that is synchronized with the system clock. Synchronous burst static RAM is used in a computer s L2 cache, where frequently accessed information is stored for fast retrieval by the CPU. Synchronous burst static RAM is faster than asynchronous static RAM but is limited to a maximum bus speed of 66 MHz. Computers running at faster speeds can use another form of cache memory known as pipeline burst static RAM. Also called: sync SRAM. See also L2 cache, static RAM. Compare asynchronous static RAM, dynamic RAM, pipeline burst static RAM.

synchronous communications n. Computer-to-computer communications in which transmissions are synchronized by timing between the sending and receiving machines.

Synchronous Data Link Control n. See SDLC.

Synchronous Digital Hierarchy n. An ITU recommendation implemented in Europe and similar in most respects to the SONET standard used in North America and Japan. See also SONET.

synchronous DRAM n. See SDRAM.

synchronous graphics RAM n. A form of dynamic RAM optimized for the high-speed, high-volume data transfers required by 3D graphics, video, and other memory-intensive applications. Used primarily on video accelerator cards, synchronous graphics RAM makes use of burst operations and includes features such as block writes that increase efficiency in retrieving and writing graphics data to the screen. Acronym: SGRAM. See also block, mask.

synchronous idle character n. See SYN.

synchronous operation n. 1. Any procedure under the control of a clock or timing mechanism. Compare asynchronous operation. 2. In communications and bus operation, data transfer accompanied by clock pulses either embedded in the data stream or provided simultaneously on a separate line.

synchronous operation n. 1. Two or more processes that depend on the occurrences of specific events such as common timing signals. 2. A data transmission method in which there is constant time between successive bits, characters, or events. The timing is achieved by the sharing of a single clock. Each end of the transmission synchronizes itself with the use of clocks and information sent along with the transmitted data. Characters are spaced by time and not by start and stop bits. 3. A function call that blocks execution of a process until it returns. See also asynchronous operation.

Synchronous Optical Network n. See SONET.

synchronous protocol n. A set of guidelines developed to standardize synchronous communications between computers, usually based on either bit stream transmission or recognized character codes. Examples include the character-oriented binary synchronous (BISYNC) protocol and the bit-oriented High-level Data Link Control (HDLC) and Synchronous Data Link Control (SDLC) protocols. See also BISYNC, HDLC, SDLC.

synchronous transmission n. Data transfer in which information is transmitted in blocks (frames) of bits separated by equal time intervals. Compare asynchronous transmission.

synchronous UART n. A universal asynchronous receiver/transmitter (UART) that supports synchronous serial transmission, where the sender and receiver share a timing signal. See also UART.

sync signal n. Short for synchronization signal. The part of a raster-display video signal that denotes the end of each scan line (the horizontal sync signal) and the end of the last scan line (the vertical sync signal).

sync SRAM n. See synchronous burst static RAM.

SYN flood n. A method of overwhelming a host computer on a network, especially the Internet, by sending the host a high volume of SYN (synchronization) packets requesting a connection, but never responding to the acknowledgement packets returned by the host. A SYN flood is a form of denial of service attack. See also denial of service attack. Compare Ping of Death.

synonym n. 1. A word that is an equivalent of another word. When used in reference to data input, for example, the verbs type and keyboard are synonyms. 2. In hashing, one of two distinct keys that produce the same hash address. See also hash².

syntax n. The grammar of a language; the rules governing the structure and content of statements. See also logic, programming language, syntax error. Compare semantics (definition 1).

syntax checker n. A program for identifying errors in syntax for a programming language. See also syntax, syntax error.

syntax error n. An error resulting from a statement that violates one or more of the grammatical rules of a language and is thus not legal. See also logic, semantics (definition 1), syntax.

synthesis n. The combining of separate elements to form a coherent whole, or the result of such a combining (for example, combining digital pulses to replicate a sound, or combining digitized words to synthesize human speech). See also speech synthesis.

synthesizer n. A computer peripheral, chip, or stand-alone system that generates sound from digital instructions rather than through manipulation of physical equipment or recorded sound. See also MIDI.

.sys n. A file extension for system configuration files.

sysadmin n. The usual logon name or e-mail address for the system administrator of a UNIX-based system. See also system administrator.

sysgen n. See system generation.

sysop n. Short for system operator. The overseer of a bulletin board system (BBS) or a small multiuser computer system.

Sys Req key n. Short for System Request key. A key on some IBM and compatible keyboards that is intended to provide the same function as the Sys Req key on an IBM mainframe computer terminal: to reset the keyboard or to change from one session to another.

system n. Any collection of component elements that work together to perform a task. Examples are a hardware system consisting of a microprocessor, its allied chips and circuitry, input and output devices, and peripheral devices; an operating system consisting of a set of programs and data files; or a database management system used to process specific kinds of information.

system administrator n. The person responsible for administering use of a multiuser computer system, communications system, or both. A system administrator performs such duties as assigning user accounts and passwords, establishing security access levels, allocating storage space, and watching for unauthorized access to prevent virus or Trojan horse programs from entering the system. Also called: sysadmin. See also superuser, Trojan horse, virus. Compare sysop.

system area network n. See storage area network.

system board n. See motherboard.

system clock n. See clock (definition 1).

system console n. The control center of a computer system, primarily with reference to mainframe and minicomputers. In networked or distributed systems, one workstation is designated as the system administrator s; this workstation is analogous to the LAN system console. See also console, LAN.

system conversion n. Changing from one operating system to another for example, from Windows 98 to Windows 2000, UNIX, or OS/2.

system development n. The process of defining, designing, testing, and implementing a new system.

system disk n. A disk that contains an operating system and can be used to boot a computer. Also called: startup disk. See also boot², operating system.

system error n. A software condition that renders the operating system incapable of continuing to function normally. This type of error usually requires rebooting the system.

system failure n. The inability of a computer to continue functioning, usually caused by software rather than hardware.

System file n. A resource file on the Macintosh that contains the resources needed by the operating system, such as fonts, icons, and default dialog boxes.

System folder n. The Macintosh file folder (directory) that contains the System file and other vital files, such as Finder, device drivers, INIT files, and control panel files. See also control panel, Finder, INIT, System file.

system font n. On the Macintosh and in some PC applications, the font used by the computer for on-screen text, such as menu titles and items (but not on-screen text within a word processor or other application). See also font.

system generation n. The process of configuring and installing system software for a particular set of hardware components. Complex operating systems such as UNIX are shipped with device drivers and utilities that are often not relevant to a particular hardware configuration; putting together only the necessary components, as well as specifying important system characteristics, is part of the system generation process. Also called: sysgen.

system heap n. See heap (definition 1).

system.ini n. In Windows 3.x, the initialization file used to store the hardware configuration information necessary to run the Windows operating environment. The system.ini file was replaced by the registry database in Windows 9x and in Windows NT. See also ini file.

system life cycle n. An information system s useful life. At the end of a system s life cycle it is not feasible to repair or expand it, so it must be replaced.

system memory n. See memory.

System Object Model n. See SOM (definition 1).

system on a chip n. See SOC.

system operator n. See sysop.

system prompt n. See prompt (definition 1).

system recovery n. Processing that takes place after a system failure in order to restore a system to normal operation. System recovery takes place after the operating system is initiated. It sometimes requires that tasks in process during the failure be backed out of and that structures in memory during the failure be reconstructed.

System Registry n. See registry.

system replacement n. See replacement strategy.

System Request key n. See Sys Req key.

system resource n. On the Macintosh, any of numerous routines, definitions, and data fragments that are stored in the Macintosh System file, such as floating-point arithmetic routines, font definitions, and peripheral drivers. See also resource (definition 2).

systems analysis n. The examination of a system or problem with the goal of either improving an existing system or designing and implementing a new one. As a science, systems analysis is related to cybernetics, a branch of engineering that studies the behavior of systems.

systems analyst n. A person who works on designing and developing systems. Systems analysts generally combine technical, managerial, and human-relations activities in order to complete their analyses.

Systems Application Architecture n. See SAA.

systems integration n. The development of a computer system for a particular customer by combining products from different original equipment manufacturers (OEMs).

Systems Management Server n. A Microsoft Back Office component that provides services for centralized network management. Acronym: SMS.

Systems Network Architecture n. See SNA.

system software n. The collection of programs and data that make up and relate to the operating system. Compare application.

systems programming n. The development or maintenance of programs designed to execute as part of an operating system, such as I/O routines, user interfaces, command-line interpreters, and task-scheduling and memory management routines.

system support n. The provision of services and material resources for the use, maintenance, and improvement of an implemented system.

system timer n. See clock (definition 1).

system unit n. See console.

System V n. A version of the UNIX system provided by AT&T and others. It is both a standard (principally controlled by AT&T) and a set of commercial products. See also UNIX.