Q

Q

QAM n. See quadrature amplitude modulation, queued access method.

QBasic n. An interpreted language. QBasic is a dialect of Basic created by Microsoft for the MS-DOS platform. This language is no longer supported.

QBE n. See query by example.

QIC n. 1. Acronym for quarter-inch cartridge. A storage technology used with tape backup drives and cartridges. A means of backing up data on computer systems, QIC represents a set of standards devised to enable tapes to be used with drives from different manufacturers. The QIC standards specify the length of tape, the number of recording tracks, and the magnetic strength of the tape coating, all of which determine the amount of information that can be written to the tape. Older QIC-80 drives can hold up to 340 MB of compressed data. Newer versions can hold more than 1 GB of information. 2. A consortium of quarter-inch tape manufacturers. Quarter-Inch Cartridge Drive Standards Inc. (QIC) establishes standards for the production of quarter-inch tapes. For example, QIC-40 and QIC-80, designed to use a PC s floppy disk drive controller, are called the floppy tape standards.

QOS or QoS n. See quality of service.

quadbit n. A set of 4 bits representing one of 16 possible combinations. In communications, quadbits are a means of increasing transmission rates by encoding 4 bits at a time, instead of 1 or 2. The 16 quadbits are 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, and 1111. Compare nibble.

quadrature amplitude modulation n. In communications, an encoding method that combines amplitude modulation and phase modulation to create a constellation of signal points, each representing one unique combination of bits that can be identified with one possible state that the carrier wave can be in. Acronym: QAM. See also amplitude modulation, constellation, phase-shift keying, trellis-coded modulation.

quadrature encoding n. The most common method used to determine in which direction a mouse is moving. In mechanical mice, movement of the mouse ball is translated into horizontal or vertical movement by a pair of turning disks, one disk for horizontal movement and one disk for vertical movement, each of which makes and breaks contact with two sensors located on it. The two sensors are placed out of phase with each other, and the mouse notes which sensor receives contact first. The phrase quadrature encoding comes from the fact that each sensor sends a square-wave signal 90 degrees out of phase with the other. If the first signal occurs before the second, the mouse is assumed to have been moved in one direction; if the second signal occurs before the first, the mouse is assumed to have been moved in the opposite direction. See also mechanical mouse, mouse, optomechanical mouse.

quality assurance n. A system of procedures carried out to ensure that a product or a system adheres or conforms to established standards. Also called: quality control.

quality of service n. 1. Generally, the handling capacity of a system or service; the time interval between request and delivery of a product or service to the client or customer. 2. In computer technology, the guaranteed throughput (data transfer rate) level.

quantity n. A number positive or negative, whole or fractional that is used to indicate a value.

quantize vb. To divide an element into separate, distinct units (quanta) and to assign a value to each resulting unit, especially in the domain of time. Compare digitize.

quantum n. 1. In communications, the unit resulting from division of a signal by quantization. 2. A portion of time allotted on a time-sharing system. Compare time slice. 3. An amount of something; for example, in physics, a unit of radiant energy.

quantum bit n. See qubit.

quantum computing n. A theoretical design for computers based on quantum mechanics. Unlike classic (current) digital computers, which calculate sets of values sequentially because a single bit can represent only 1 or 0 at any given time, a quantum computer is based on the ability of each bit to represent more than one value at the same time. Because each quantum bit called a qubit represents multiple values, a quantum computer can be in multiple states simultaneously and can thus work on numerous problems at the same time to offer far more computing power than is currently available. Quantum computing is under investigation by the United States Defense Advanced Research Projects Agency (DARPA) and other groups. Although atoms of hydrogen and carbon have been used to create the rudiments of a quantum computer, the technology is still in its infancy.

quarter-inch cartridge n. See QIC (definition 1).

Quartz n. The 2-D drawing engine that forms the imaging foundation of the Mac OS X Aqua interface. The Quartz graphics application programming interface (API) is based on Adobe s Portable Document Format (PDF) standard.

quartz crystal n. A precisely shaped and precisely sized piece of the mineral quartz, used for its piezoelectric properties. When a voltage is applied to a quartz crystal, it vibrates at a frequency determined by its size and shape. Quartz crystals are commonly used to control the frequency of oscillator circuits such as the clocks in microcomputers. See also piezoelectric.

quasi-language n. A derogatory term for any programming language that, because of deficiencies, is not suitable for any serious work.

qubit n. Short for quantum bit. The bits (currently, atomic particles) that make up the theoretical machines known as quantum computers. Qubits are unlike bits in current computers in that they exist in more than one state at the same time. They can, therefore, represent both 0 and 1 simultaneously. Qubits, like quantum computers, are based on the science of quantum mechanics.

query¹ n. A specific set of instructions for extracting particular data.

query² vb. To extract data from a database and present it for use.

query by example n. A simple-to-use query language implemented on several relational database management systems. Using query by example, the user specifies fields to be displayed, intertable linkages, and retrieval criteria directly onto forms displayed on the screen. These forms are a direct pictorial representation of the table and row structures that make up the database. Thus, the construction of a query becomes a simple checkoff procedure from the viewpoint of the user. Acronym: QBE.

query language n. A subset of the data manipulation language; specifically, that portion relating to the retrieval and display of data from a database. It is sometimes used loosely to refer to the entire data manipulation language. See also data manipulation language.

question mark n. See ?.

queue¹ n. A multi-element data structure from which (by strict definition) elements can be removed only in the same order in which they were inserted; that is, it follows a first in, first out (FIFO) constraint. There are also several types of queues in which removal is based on factors other than order of insertion for example, some priority value assigned to each element. See also deque, element (definition 1). Compare stack.

queue² vb. To place (an item) in a queue.

queued access method n. A programming technique that minimizes input/output delays by synchronizing the transfer of information between the program and the computer s input and output devices. Acronym: QAM.

queuing n. In networking, the process of buffering data in preparation for transmission. See also fair queuing, first in, first out, last in, first out, weighted fair queuing.

QuickDraw n. On the Apple Macintosh, the built-in group of routines within the operating system that controls the display of graphics and text. Application programs call QuickDraw for on-screen displays. See also Toolbox.

QuickDraw 3-D n. A version of the Macintosh QuickDraw library that includes routines for doing 3-D graphics calculations. See also QuickDraw.

Quicken n. Financial-management software from Intuit, Inc. The personal-finance version, introduced by Intuit in 1984, includes tools for balancing and tracking bank accounts and investments, budgeting, paying bills, planning and preparing tax returns, financial planning, and estate planning. A small-business version, Quicken Home & Business, adds tools for business-related matters, such as invoicing and accounts receivable and payable.

quicksort n. An efficient sort algorithm, described by C.A.R. Hoare in 1962, in which the essential strategy is to divide and conquer. A quicksort begins by scanning the list to be sorted for a median value. This value, called the pivot, is then moved to its final position in the list. Next, all items in the list whose values are less than the pivot value are moved to one side of the list, and the items with values greater than the pivot value are moved to the other side. Each resulting side is sorted the same way, until a fully sorted list results. See also sort algorithm. Compare bubble sort, insertion sort, merge sort.

QuickTime n. Software components developed by Apple for creating, editing, publishing, and viewing multimedia content. QuickTime, which supports video, animation, graphics, 3-D, VR (virtual reality), MIDI, music, sound, and text, has been part of the Mac OS since version 7 of the operating system and is used in many Macintosh applications. Windows applications can also run QuickTime files but require the installation of special player software. QuickTime is often used on the Web to provide Web pages with video and animation. Most Web browsers support plug-ins for running these types of files. QuickTime is also part of the new MPEG-4 specification. See also MPEG-4.

Quick View n. A feature, optionally installed as part of Windows 9x, that provides a set of file viewers for previewing the contents of files without having to start the application(s) that created them. The feature is accessed through the Quick View command, available either from the File menu or by right-clicking a filename. If the feature has been installed but the file type is not supported by a viewer, the Quick View command does not appear.

quiet answer n. A telephone-answering protocol in which incoming calls are answered with silence instead of a tone signal. Some telephone-switching systems use quiet answering. These switching systems expect the caller to provide another phone number, code, or extension after the quiet answer.

quit¹ n. 1. An FTP command that instructs the server to drop the current connection with the client from which it received the command. 2. A command in many applications for exiting the program.

quit² vb. 1. To stop in an orderly manner. 2. To execute the normal shutdown of a program and return control to the operating system. Compare abort, bomb, crash(definition 1), hang.

QWERTY keyboard n. A keyboard layout named for the six leftmost characters in the top row of alphabetic characters on most keyboards the standard layout of most typewriters and computer keyboards. Compare Dvorak keyboard.