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.

safe mode

n. In some versions of Windows, such as Windows 95, a boot mode in which most drivers and peripherals are disconnected to allow the user to correct some problem with the system. This will occur if the system was not shut down properly or if the system failed to complete a boot-up. See also boot¹.

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.

SAP

n. See Service Advertising Protocol.

SAPI

n. Acronym for Speech Application Programming Interface. A feature in Windows 95 and Windows NT that allows applications to include speech recognition or convert text to speech. Also called Speech API. See also speech recognition.

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.

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.

scalable

adj. Of or relating to the characteristic of a piece of hardware or software that makes it possible for it to expand to meet future needs. 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.

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.

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.

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).

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. Also called point chart, point 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.

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.

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 block¹ (definition 3), global, local. 2. In electronics, slang for oscilloscope. See also oscilloscope.

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.

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 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 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 also phosphor.

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.

screen shot

n. An image that shows all or part of a computer display. The illustration shown here as well as entries alert box, cell, and menu bar, for example, are screen shots.

ScreenTips

n. In an application, notes that appear on the screen to provide information about a feature or dialog box.

script

n. A program consisting of a set of instructions to an application or utility program. The instructions usually use the rules and syntax of the application or utility. 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.

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 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.

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 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. Compare ESDI, IDE.

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. 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 also bus, connector (definition 1), SCSI device.

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 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.

SDK

n. Acronym for software developer's 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.

SDRAM

n. See synchronous DRAM.

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 key words 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, AliWeb, and Excite. Most search engines reside on a server. See also agent (definition 2), FTP, 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 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 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.

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.

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 Electronics Transactions protocol

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

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. A proposed open standard developed by Netscape Communications for establishing a secure communications channel to prevent the interception of critical information, such as credit card numbers. The primary purpose of Secure Sockets Layer is to enable secure electronic financial transactions on the World Wide Web, although 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. Compare S-HTTP. Acronym: SSL.

Secure Transaction Technology

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

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. See also authentication, authorization, encryption, virtual private network (definition 1). Acronym: S/WAN.

security

n. Protection of a computer system and its data from harm or loss. 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).

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.

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.

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.

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

n. To transmit a message or file through a communications channel.

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 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.

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 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. See also infrared port. Acronym: SIR.

SerialKeys

n. A feature of Windows 95 that, in conjunction with a communications aid interface device, allows keystrokes and mouse controls to be accepted through a computer's serial port.

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 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.

serif¹

adj. Marked by the use of serifs. For example, Goudy is a serif typeface, whereas Helvetica is a sans serif typeface. See also serif². Compare sans serif.

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 client/server architecture. Compare client (definition 3).

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 computers that work together as a single system. A server cluster presents the appearance of a single server to a client.

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 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 also HTML, server (definition 2), URL.

server-side includes

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. 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. 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 offline, it uses the protocol to announce that it is no longer available. See also server (definition 1). Acronym: SAP.

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 Pack

n. A service pack is a means by which product updates are distributed. It keeps the product current and extends and updates your computer's functionality so you'll never have to worry about becoming out of date. A service pack includes updates, system administration tools, drivers, and additional components. All are conveniently bundled for easy downloading. A service pack is cumulative; that is, each new service pack contains all the fixes in previous service packs, as well as any new fixes.

Service Release

n. A service release is a collection of bug fixes that have been introduced since a product's release. New feature updates are not included in a service release. A service release may not be cumulative. In other words, you may need to apply an earlier service release before you apply the most current one.

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 networking model that manages communication between remote users or processes. See also ISO/OSI model, session layer.

session layer

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

set¹

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

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.

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

setup wizard

n. In Microsoft Windows, a structured series of questions and options that leads a user through the process of installing a new program.

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 grammar-like 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.

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 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.

share

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

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 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 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. In Windows NT, any resource made available to network users, such as directories, files, and printers.

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.

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.

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 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.

Shift+click

or Shift click 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.

Shockwave

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

shortcut

n. In Windows 95, an icon on the desktop that a user can double-click on to immediately access a program, a text or data file, or a Web page. See also symbolic link.

shortcut key

See accelerator.

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.

ShowSounds

n. In Windows 95, 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.

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.

SHTML

n. Acronym 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 includes.

S-HTTP

n. Acronym for Secure Hypertext Transfer Protocol. A proposed extension to HTTP that supports various encryption and authentication measures to keep all transactions secure from end to end.

shut down

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

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 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.

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).

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.

signature

n. 1. A sequence of data used for identification, such as text appended to an e-mail message or 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.

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.

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. See also gate (definition 1), rectifier. Acronym: SCR.

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.

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.

SIMM

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

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. See also communications protocol, TCP/IP. Compare CCITT X series, Post Office Protocol. Acronym: SMTP.

Simple Network Management Protocol

n. See SNMP.

simulation

n. The imitation of a physical process or 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 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.

single inline memory module

n. See SIMM.

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.

site

n. See Web site.

site license

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

slave

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

sleep²

vb. To suspend operation without terminating.

sleeve

n. See disk envelope.

SLIP

n. Acronym for Serial Line Internet Protocol. A data link protocol that allows transmission of IP data packets over dial-up telephone connections, thus enabling a computer or a local area network to be connected to the Internet or some other network. 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. See expansion slot.

small caps

n. A font of capital letters that are smaller than the standard capital letters in that typeface. THIS TEXT IS IN SMALL CAPS.

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 quotes

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

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.

SMDS

n. Acronym for Switched Multimegabit Data Services. A very high-speed, switched data transport service that connects local area networks and wide area networks through the public telephone network.

smiley

n. See emoticon.

S/MIME

n. Acronym for Secure/Multipurpose Internet Mail Extensions. An Internet e-mail security standard that makes use of public key encryption. See also public key encryption.

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 whatever 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.

SMTP

n. See Simple Mail Transfer Protocol.

SNA

n. Acronym for Systems Network Architecture. A widely used communications framework developed by IBM to define network functions and establish standards for enabling computers to exchange and process data.

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. See plug-in.

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.

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.

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. 2. The receptacle part of a connector, which receives a plug. See also female connector.

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 boot

n. See warm boot.

soft copy

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

soft font

n. See downloadable font.

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.

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 package

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

software portability

n. See portable (definition 1).

software program

n. See application.

software publisher

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

software publishing

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

Solaris

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

solid-state memory

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

SONET

n. Acronym for Synchronous Optical Network. A category of fiber-optic communication standards that permits extremely high-speed transmission (51.84 Mbps to 2.48 Gbps).

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, quick sort.

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 editor

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

SoundSentry

n. An optional Windows 95 feature for users with hearing impairments or users who operate a computer in a noisy environment that instructs Windows to produce a visual cue such as a screen flash or a blinking title bar whenever a system beep occurs.

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 in a high-level or assembly language that are not directly readable by a computer. Compare object code.

source drive

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

Spacebar

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

spam

n. 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 (usually commercial or religious) to a huge number of people at minimal cost.

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, spam.

SPARC

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

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.

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 places their addresses and content-related information in a database, which can be accessed with a search engine. Spiders are generally considered to be a type of bot, or Internet robot. 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.

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.

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).

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 model. Compare IPX. 2. Acronym for simplex. See simplex transmission.

SQL

n. See structured query language.

SSL

n. See Secure Sockets Layer.

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.

stand-alone

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 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 represent the opinions or policies of the organization from whose e-mail system the message originated.

Standard Generalized Markup Language

n. See SGML.

star-dot-star

n. A file specification (*.*) using the asterisk wildcard, which means "any combination of filename and extension" in operating systems such as MS-DOS. See also asterisk (definition 2), wildcard character.

star network

n. A local area network (LAN) 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. Compare bus network, ring network.

Start button

n. In Microsoft Windows 95, 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.

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.

state-of-the-art

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

static²

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

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. See also cache, RAM. Compare dynamic RAM. Acronym: SRAM.

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).

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 Microsoft Windows, 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.

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.

StickyKeys

n. An accessibility feature built into Macintosh computers and available for Windows and DOS 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.

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 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.

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.

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.

string

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

structured query language

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

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.

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 used with a graphics tablet, usually attached to the tablet with a cord. Also called pen. See also graphics tablet, puck.

subdirectory

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

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." The lowest level of the tree consists of links to specific Web pages. An example of a World Wide Web subject tree is Yahoo! See also Yahoo!.

submenu

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

subnet

n. A network that is a component of a larger network.

subnet mask

n. See address mask.

subnotebook computer

n. A portable computer that is smaller and lighter than a conventional laptop computer.

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.

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).

suite

n. 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. See protocol stack.

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.

supercomputer

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

superscript

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

support¹

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

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.

surge

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

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.

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/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.

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 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 (/).

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 network

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

switched virtual circuit

n. See SVC.

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 link file. 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.

symmetric multiprocessing

n. See SMP.

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.

synchronous DRAM

n. 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. Acronym: SDRAM.

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.

sysadmin

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

sysop

n. Short for system operator. The overseer of a BBS or a small multiuser computer system.

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 Trojan horse, virus. Compare sysop.

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 support

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

System V