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J2EE n. Acronym for Java 2 Platform Enterprise Edition. An application server framework from Sun Microsystems, Inc., for the development of distributed applications. It includes all the previous Java APIs targeted for multi-tiered distributed enterprise information systems. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, Web-based applications. See also application programming interface, Enterprise Java Beans, IDL, Java, JDBC, Jini, JMS, JNDI, JSP, JTA, JTS, RMI-IIOP.

J n. A high-level programming language created by Kenneth Iverson, developer of APL, and Roger Hui. J is a successor language to APL that may be run on many platforms, including Windows 95, Windows NT, Macintosh, Linux, RS/6000, and Sun Sparc. Like APL, J is used primarily by mathematicians. See also APL.

jabber n. A continuous stream of random data transmitted over a network as the result of some malfunction.

Jabber n. An XML-based instant messaging system. Jabber software is available for most operating systems and allows user access to other instant messaging services. Jabber is an open source application overseen by Jabber.org.

jack n. A connector designed to receive a plug. A jack is commonly used in making audio and video connections.

jacket n. See disk jacket.

jack in vb. 1. To log on to a computer. 2. To connect to a network or BBS, especially for purposes of entering an IRC or a virtual reality simulation, such as a MUD. (To leave is to jack out.) See also IRC, MUD.

jack out vb. 1. To log off a computer. 2. To disconnect from a network or online bulletin board system. See also jack in, log on.

Jacquard loom n. The first machine that used punched cards to control its operation. In this loom, developed in 1801 by French inventor Joseph-Marie Jacquard, up to 24,000 cards were placed on a rolling drum. Where a hole was punched on a card, one of a set of rods could pass through and select a particular thread to be woven into the pattern. Jacquard was awarded a medal by the Emperor Napoleon for his invention. Later in the nineteenth century, punched cards were used in Charles Babbage s computerlike Analytical Engine and in Herman Hollerith s statistical tabulating machine. See also Analytical Engine, Hollerith tabulating/recording machine.

jaggies n. The stairsteps that appear in diagonal lines and curves drawn at low resolutions in computer graphics. Also called: aliasing.

Janet n. Short for the Joint Academic Network. A wide area network in the United Kingdom that serves as the principal backbone for the Internet in that country. See also backbone (definition 1).

.jar n. A file name extension that identifies a compressed JAR (Java Archive) file. Note: By changing the .jar extension to .zip, you can use popular extraction tools such as PKZIP or WINZIP to look at a .jar file s contents. See also compressed file, JAR, PKZIP, .zip.

JAR n. Acronym for Java Archive file. JAR files allow Java developers to efficiently deploy Java classes and their associated resources. The elements in a JAR file are compressed just as in a standard zip file. JAR files include a security mechanism and a special META-INF directory that contains administrative information about the contents of the files. Using a combination of a digital signature and the META-INF data, JAR files can be signed to ensure authenticity and security. See also .jar.

Java n. An object-oriented programming language developed by Sun Microsystems, Inc. Similar to C++, Java is smaller, more portable, and easier to use than C++ because it is more robust and it manages memory on its own. Java was also designed to be secure and platform-neutral (meaning that it can be run on any platform) through the fact that Java programs are compiled into bytecode, which is not refined to the point of relying on platform-specific instructions and runs on a computer in a special software environment known as a virtual machine. This characteristic of Java makes it a useful language for programming Web applications, since users access the Web from many types of computers. Java is used in programming small applications, or applets, for the World Wide Web, as well as in creating distributed network applications. See also bytecode, Java applet, Jini, object-oriented programming.

Java applet n. A Java class that is loaded and run by an already-running Java application such as a Web browser or an applet viewer. Java applets can be downloaded and run by any Web browser capable of interpreting Java, such as Internet Explorer, Netscape Navigator, and HotJava. Java applets are frequently used to add multimedia effects and interactivity to Web pages, such as background music, real-time video displays, animations, calculators, and interactive games. Applets can be activated automatically when a user views a page, or they may require some action on the part of the user, such as clicking on an icon in the Web page. See also applet, Java.

JavaBean n. A Java component architecture defined in the JavaBeans specification developed by Sun Microsystems. A JavaBean, or Bean, is a reusable application component an independent code segment that can be combined with other JavaBean components to create a Java applet or application. The JavaBean concept emphasizes the platform-independence of the Java language, in which ideally a program, once written, can run on any computing platform. JavaBeans are similar to Microsoft s ActiveX controls. ActiveX controls, however, can be developed in different programming languages but executed only on a Windows platform. JavaBeans can be developed only in the Java programming language but ideally can run on any platform. See also ActiveX, Java.

Java Card n. An application programming interface (API) from Sun Microsystems, Inc., that allows Java applets and programs to run on smart cards and other devices with limited memory. Java Card uses a Java Card Virtual Machine designed for severely memory-constrained devices. See also applets, Java Card Virtual Machine, smart card (definition 2).

Java Card Virtual Machine n. An ultra-small-footprint, highly optimized foundation of a runtime environment within the Java 2 Platform Micro Edition. Derived from the Java Virtual Machine (JVM), it is targeted at smart cards and other severely memory-constrained devices. The Java Card Virtual Machine can run in devices with memory as small as 24 KB of ROM, 16 KB of EEPROM, and 512 bytes of RAM. See also EEPROM, Java Card, RAM, ROM.

Java chip n. An implementation on a single integrated circuit of the virtual machine specified for execution of the Java programming language. Such chips, which are being developed by Sun Microsystems, Inc., could be used in very small devices and as controllers for appliances. See also integrated circuit, Java, virtual machine.

Java-compliant browser n. A Web browser with support for the Java programming language built into it. Most current Web browsers are Java-compliant. See also Java, Web browser.

Java Developer s Kit n. A set of software tools developed by Sun Microsystems, Inc., for writing Java applets or applications. The kit, which is distributed free, includes a Java compiler, interpreter, debugger, viewer for applets, and documentation. Acronym: JDK. See also applet, Java, Java applet.

Java Foundation Classes n. A Java-based set of class libraries developed by Sun Microsystems, Inc. Encompassing fundamentals of the Internet Foundation Classes created by Netscape Communications Corp., the Java Foundation Classes extend the Java Abstract Window Toolkit (AWT) by providing graphical user interface components for use in developing commercial and Internet-related Java applications. See also Abstract Window Toolkit, Application Foundation Classes, Internet Foundation Classes, Java, JavaBean, Microsoft Foundation Classes.

Java HotSpot n. A Java performance engine introduced by Sun Microsystems, Inc., in 1999 that is designed to run Java applications faster than just-in-time (JIT) compilers. The core of Java HotSpot, and the feature for which it is named, is its ability to perform adaptive optimization the identification and optimization of hot spots, or sections of performance-critical code. Improved garbage collection (freeing of memory occupied by objects no longer in use) and better multithreading are additional features designed to contribute to increased performance. See also Java.

Java IDL n. Short for Java Interface Definition Language. A Java technology that provides CORBA interoperability and connectivity capabilities for the Java platform. These capabilities enable Java applications to invoke operations on remote network services using the Object Management Group Interface Definition Language and Internet Inter-ORB Protocol. See also CORBA, IDL, J2EE, RMI-IIOP.

JavaMail n. An API in the Sun Microsystems, Inc., Java platform for sending and receiving mail. A set of abstract APIs that model a mail system, JavaMail provides a platform-independent and protocol-independent framework to build Java-based e-mail client applications. See also application programming interface, e-mail, J2EE.

Java Management Application Programming Interface n. A set of application programming interface specifications, proposed by Sun Microsystems, Inc., to enable the Java language to be used for network management. Acronym: JMAPI. See also application programming interface, Java.

JavaOS n. An operating system designed to run applications written in the Java programming language. JavaOS was created by JavaSoft, an operating company of Sun Microsystems, Inc., to run the Java Virtual Machine (JVM) directly on microprocessors, and thus eliminate the need for a resident operating system. JavaOS is small and designed for network computers, as well as devices ranging from game machines to pagers and cellular telephones. See also Java.

JavaScript n. A scripting language developed by Netscape Communications and Sun Microsystems that is loosely related to Java. JavaScript, however, is not a true object-oriented language, and it is limited in performance compared with Java because it is not compiled. Basic online applications and functions can be added to Web pages with JavaScript, but the number and complexity of available application programming interface functions are fewer than those available with Java. JavaScript code, which is included in a Web page along with the HTML code, is generally considered easier to write than Java, especially for novice programmers. A JavaScript-compliant Web browser, such as Netscape Navigator or Internet Explorer, is necessary to run JavaScript code. See also application programming interface, HTML, scripting language. Compare Java.

JavaServer Pages n. See JSP.

Java Speech Grammar Format n. A platform-independent grammar description format developed for use with speech recognition systems. Java Speech Grammar Format is used extensively with Voice XML and can be used with most speech recognition systems and related applications. Acronym: JSGF.

Java Virtual Machine n. The environment in which Java programs run. The Java Virtual Machine gives Java programs a software-based computer they can interact with. (Programs, even the most seemingly unchallenging ones designed for children or entertainment, must run within an environment from which they can use memory, display information, gather input, and so on.) Because the Java Virtual Machine is not a real computer but exists in software, a Java program can run on any physical computing platform, such as a Windows 9x computer or a Macintosh, equipped with an interpreter usually an Internet browser that can carry out the program s instructions and a Java Virtual Machine that provides the hardware on which the program can run. Acronym: JVM.

JCL n. Acronym for Job Control Language. A command language used in IBM OS/360 mainframe systems. JCL is used to launch applications and specifies information on running time, program size, and the program files used for each application. See also command language.

JDBC n. A Java API designed to provide access to relational databases and other tabular material, such as spreadsheets and flat files. Using JDBC, a developer can create a cross-platform Java application that can connect with, and send SQL statements to, a number of different relational databases. Although it is commonly thought to stand for Java Database Connectivity, JDBC is the name of the technology; it is not an acronym.

JDK n. See Java Developer s Kit.

jDoc n. A cross-platform, interactive format for display, distribution, and interaction with live Web pages. jDoc documents are small in size and can be embedded in HTML documents to offer client-side interactivity. jDoc was created by EarthStones and is an extension to Sun s Java platform.

JetSend Protocol n. A platform-independent communications protocol developed by Hewlett-Packard to enable direct device-to-device communication. The JetSend protocol is designed to provide JetSend-enabled devices with the ability to exchange information and data without the need for device drivers or reliance on servers or user intervention. The protocol is intended for use with printers, scanners, fax machines, and other such information appliances and was developed to simplify and improve interoperability between and among a wide range of devices.

Jet SQL n. A query language. Jet SQL is a dialect used by the Microsoft Access application, specifically by the Microsoft Jet database engine, to extract, manipulate, and structure data that resides in a relational database management system (RDBMS). Jet SQL is based largely on the ANSI SQL-92 standard, with additional extensions.

jewel box n. A clear plastic container used to package and store a compact disc. Also called: jewel case.

JFC n. See Java Foundation Classes.

JFIF n. Acronym for JPEG File Interchange Format. A means of saving photographic images stored according to the Joint Photographic Experts Group image compression technique. JFIF represents a common language file format in that it is designed specifically to allow users to transfer JPEG images easily between different computers and applications. See also JPEG, TIFF JPEG.

Jini n. A technical specification developed by Sun Microsystems that uses a small piece (48 KB) of Java code to allow any network device with a Java Virtual Machine (JVM) to announce its availability and provide its services to any other device connected to the same network. Jini is based on the concept of creating a federation of self-configuring devices capable of transparently exchanging code when necessary to simplify interactions between network devices. See also Java.

JIT adj. See just-in-time.

jitter n. 1. Small vibrations or fluctuations in a displayed video image caused by irregularities in the display signal. Jitter is often visible in the form of horizontal lines that are of the same thickness as scan lines. 2. A rough appearance in a fax caused by dots that are incorrectly recorded during the scanning process and thus wrongly positioned in the output. 3. In digital communication, distortion caused by lack of synchronization of signals.

JMAPI n. See Java Management Application Programming Interface.

JMS n. Acronym for Java Messaging Service. In the J2EE network platform, JMS is an API for using enterprise messaging systems such as IBM MQ Series, TIBCO Rendezvous, and others. See also application programming interface, J2EE.

JNDI n. Acronym for Java Naming and Directory Interface. A set of APIs in the J2EE platform from Sun Microsystems, Inc., that assists with the interfacing to multiple naming and directory services. See also application programming interface, J2EE.

job n. A specified amount of processing performed as a unit by a computer. On early mainframe computers, data was submitted in batches, often on punched cards, for processing by different programs; work was therefore scheduled and carried out in separate jobs, or operations.

Job Control Language n. See JCL.

job processing n. A computing method in which a series of jobs, each consisting of one or more tasks grouped together as a computationally coherent whole, is processed sequentially. See also batch processing (definition 2).

job queue n. A list of programs or tasks waiting for execution by a computer. Jobs in the queue are often ordered according to some basis of priority. See also queue.

join n. 1. A database table operation that creates a resultant entry in another table for each entry in the one table whose key field matches that of an entry in the other. See also inner join. 2. A multiprocessing command that causes a child process to return control to its parent. See also child (definition 1), multiprocessing.

join line n. In a database query, a line that connects fields between two tables and shows how the data is related. Generally, a join line starts with an arrow just beyond the boundary of the table window pointing at the field in one table and ends just beyond the boundary of another table with an arrow pointing at the related field. The type of join indicates which records are selected for the query s result set.

Joint Photographic Experts Group n. See JPEG (definition 1).

Joliet n. An extension to the ISO 9660 (1988) standard developed to include long filenames or filenames outside the 8.3 convention. This format is used in some new CD-ROMs for operating systems, such as Windows 9x, that can handle such filenames. See also 8.3, ISO 9660, long filenames.

Josephson junction n. A cryoelectronic device that can attain extremely high circuit-switching speeds. In the Josephson effect, when two superconducting materials are in close proximity but are separated by an insulator, electric current can jump or tunnel through the gap.

journal n. A computer-based log or record of transactions that takes place in a computer or across a network. A journal could be used, for example, to record message transfers on a communications network, to keep track of system activities that alter the contents of a database, or to maintain a record of files that have been archived for storage or deleted from the system. A journal is often kept as a means of reconstructing events or sets of data should they become lost or damaged. See also audit trail.

journaled file system n. A fault-resilient file system that includes backup and recovery capabilities. When file server indexes are updated, all changes and related information are recorded and stored in a separate log. If a system failure or other abnormal interruption occurs, the system will use stored backup files to repair files corrupted in the crash. Journaled file systems are widely used for business and intranet file servers. In 2001, IBM contributed journaled file system technology to the open source community to allow development of similar file systems for Linux servers.

joystick n. A pointing device used mainly but not exclusively for computer games. A joystick has a base, on which control buttons can be mounted, and a vertical stem, which the user can move in any direction to control the movement of an object on the screen; the stem may also have control buttons. The buttons activate various software features, generally producing on-screen events. A joystick is usually used as a relative pointing device, moving an object on the screen when the stem is moved and stopping the movement when the stem is released. In industrial control applications, the joystick can also be used as an absolute pointing device, with each position of the stem mapped to a specific location on the screen. See the illustration. See also absolute pointing device, relative pointing device. Compare game pad.

Joystick.

.jpeg n. The file extension that identifies graphic image files in the JPEG format. See also JPEG.

JPEG n. 1. Acronym for Joint Photographic Experts Group. An ISO/ITU standard for storing images in compressed form using a discrete cosine transform. JPEG trades off compression against loss; it can achieve a compression ratio of 100:1 with significant loss and possibly 20:1 with little noticeable loss. 2. A graphic stored as a file in the JPEG format.

JPEG File Interchange Format n. See JFIF.

.jpg n. The file extension that identifies graphic images encoded in the JPEG File Interchange Format, as originally specified by the Joint Photographic Experts Group (JPEG). Inline graphics on World Wide Web pages are often .jpg files, such as coolgraphic.jpg. See also JPEG (definition 2).

JScript n. An interpreted, object-based scripting language that borrows from C, C++, and Java. It is Microsoft s implementation of the ECMA 262 language specification (ECMAScript Edition 3). The latest versions of JavaScript and JScript are compliant with the European Computer Manufacturing Association s ECMAScript Language Specification (ECMA 262 standard, for short).

JSGF n. See Java Speech Grammar Format.

JSP n. Short for Java Server Pages. A technology created by Sun Microsystems to enable development of platform-independent Web-based applications. Using HTML and XML tags and Java scriptlets, JSP helps Web site developers create cross-platform programs. JSP scriptlets run on the server, not in a Web browser, and generate dynamic content on Web pages, with the ability to integrate content from a variety of data sources, such as databases, files, and JavaBean components. Web site developers can concentrate on design and display of a Web site without the need for application development expertise. See also Java, JavaBean. Compare Active Server Pages.

JSP container n. Short for Java Server Pages container. In the J2EE platform, a JSP container provides the same services as a servlet container, such as providing network services over which requests and responses are sent, decoding requests, and formatting responses. 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. The JSP container is also an engine that interprets and processes JSP pages into a servlet. See also container, HTTP, HTTPS, J2EE, servlet, servlet container.

JTA n. Acronym for Java Transaction API. In the J2EE platform, JTA specifies transactions, comments, and rollbacks used by EJBs (Enterprise JavaBeans). It is a high-level, implementation-independent protocol API that allows applications and application servers to access transactions. See also application programming interface, J2EE, JTS, rollback.

JTS n. Acronym for Java Transaction Services. In the J2EE platform, JTS specifies the implementation of a transaction manager that supports JTA and implements the Java mapping of the OMG Object Transaction Service specification at a level below the API. JTS propagates transactions using the Internet Inter-ORB Protocol (IIOP). See also application programming interface, J2EE, JTA, rollback.

JUG n. Acronym for Java User Group. A user group that meets to discuss the Java programming language and the Java platform. See also user group.

Jughead n. Acronym for Jonzy s Universal Gopher Hierarchy Excavation and Display. An Internet service that enables a user to locate directories in Gopherspace through a keyword search. A Jughead server indexes keywords appearing in directory titles in top-level Gopher menus but does not index the files within the directories. To access Jughead, users must point their Gopher clients to a Jughead server. See also Gopher, Gopherspace. Compare Archie, Veronica.

jukebox n. Software that is designed to play a list of sound files in a user-specified order reminiscent of jukeboxes used to play vinyl records. See also CD-ROM jukebox.

Julian calendar n. The calendar introduced by Julius Caesar in 46 B.C. to replace the lunar calendar. The Julian calendar provided for a year of 365 days with a leap year every 4 years, or an average year length of 365.25 days. Because the solar year is slightly shorter, the Julian calendar gradually moved out of phase with the seasons and was superseded by the Gregorian calendar, introduced by Pope Gregory XIII. Compare Gregorian calendar, Hijiri calendar.

Julian date n. 1. A date expressed as the number of days elapsed since January 1, 4713 B.C. (on the Julian calendar) for example, 2,450,000 for October 9, 1995 (Gregorian). Julian dates are useful for finding elapsed times between events that may be many years apart, as in astronomy. The starting point is the beginning of the Julian Period, defined in 1583 by Joseph Scaliger as the coincidence of several cycles based on the Julian calendar. See also Gregorian calendar, Julian calendar. 2. Often (but incorrectly), a date expressed as the year and the number of days elapsed since the beginning of the year for example, 91.13 for January 13, 1991. Acronym: JD.

jumper n. A small plug or wire that can be connected between different points in an electronic circuit in order to alter an aspect of a hardware configuration. Compare DIP switch.

jump instruction n. An instruction that transfers the flow of execution from one statement or instruction to another. See also GOTO statement, transfer statement.

jump page n. See doorway page.

jump table n. See dispatch table.

Jump to .NET n. Acronym for Java User Migration Path to Microsoft .NET. A set of Microsoft technologies and services that enable Java programmers to preserve, enhance, and migrate Java language projects onto the Microsoft .NET platform. It includes tools for interoperability of existing code, Java language syntax support, and automated conversion of Java source code to C#. JUMP to .NET enables programmers using the Java language to move existing code to the Microsoft .NET platform. See also C#, .NET.

junction n. 1. Any point at which two or more electrical components are connected. 2. The contact between two types of semiconductors, such as N-type and P-type semiconductors. See also N-type semiconductor, P-type semiconductor, semiconductor.

justify vb. 1. To align vertically. 2. To align lines of text evenly along both the left and right margins of a column by inserting extra space between the words in each line. If the spacing is excessive, it can be reduced by rewriting or by hyphenating words at the ends of lines. See also align (definition 1). Compare rag.

just-in-time adj. 1. Describing a system of inventory control and industrial production management based on the Japanese kanban system. Under a just-in-time system, workers receive materials from suppliers just in time for scheduled manufacturing to take place. Line workers generally signal that they require materials by means of a card or a computerized request system. 2. Describing an action that is taken only when it becomes necessary, such as just-in-time compilation or just-in-time object activation. 3. Describing a compiler that compiles Java on the fly. Acronym: JIT. See also Java, on the fly.

JVM n. See Java Virtual Machine.