T1

or T-1 n. A T-carrier that can handle 1.544 Mbps or 24 voice channels. Although originally designed by AT&T to carry voice calls, this high-bandwidth telephone line can also transmit text and images. T1 lines are commonly used by larger organizations for Internet connectivity. See also T-carrier. Compare fractional T1, T2, T3, T4.

T.120 standard

n. A family of International Telecommunications Union (ITU) specifications for multipoint data communications services within computer applications, such as conferencing and multipoint file transfer.

T2

or T-2 n. A T-carrier that can handle 6.312 Mbps or 96 voice channels. See also T-carrier. Compare T1, T3, T4.

T3

or T-3 n. A T-carrier that can handle 44.736 Mbps or 672 voice channels. See also T-carrier. Compare T1, T2, T4.

T4

or T-4 n. A T-carrier that can handle 274.176 Mbps or 4032 voice channels. See also T-carrier. Compare T1, T2, T3.

tab character

n. A character used to align lines and columns on screen and in print. Although a tab is visually indistinguishable from a series of blank spaces in most programs, the tab character and the space character are different to a computer. A tab is a single character and therefore can be added, deleted, or overtyped with a single keystroke. The ASCII coding scheme includes two codes for tab characters: a horizontal tab for spacing across the screen or page and a vertical tab for spacing down the screen or page. See also Tab key.

Tab key

n. A key, often labeled with both a left-pointing and a right-pointing arrow, that traditionally (as in word processing) is used to insert tab characters into a document. In other applications, such as menu-driven programs, the Tab key is often used to move the on-screen highlight from place to place. Many database and spreadsheet programs allow the user to press the Tab key to move around within a record or between cells. The word tab is short for "tabulator," which was the name given to this key on typewriters, where it was used in creating tables. See also tab character.

tag

n. 1. In programming, one or more characters containing information about a file, record type, or other structure. 2. In certain types of data files, a key or an address that identifies a record and its storage location in another file. See also tag sort. 3. In markup languages such as SGML and HTML, a code that identifies an element in a document, such as a heading or a paragraph, for the purposes of formatting, indexing, and linking information in the document. In both SGML and HTML, a tag is generally a pair of angle brackets that contain one or more letters and numbers. Usually one pair of angle brackets is placed before an element, and another pair is placed after, to indicate where the element begins and ends. For example, in HTML, hello world indicates that the phrase "hello world" should be italicized. See also <>, element, emotag, HTML, SGML.

talker

n. An Internet-based synchronous communication mechanism most commonly used to support multiuser chat functions. Such systems typically provide specific commands for movement through separate rooms, or chat areas, and allow users to communicate with other users in real time through text messages, indicate simple gestures, use a bulletin board system (BBS) for posting comments, and send internal e-mail. See also BBS (definition 1), chat¹ (definition 1).

talk. newsgroups

n. Usenet newsgroups that are part of the talk. hierarchy and have the prefix talk. as part of their names. These newsgroups are devoted to debate and discussion of controversial topics. Talk. newsgroups are one of the seven original Usenet newsgroup hierarchies. The other six are comp. misc., news., rec., sci., and soc. See also newsgroup, traditional newsgroup hierarchy, Usenet.

TANSTAAFL

Acronym for "There ain't no such thing as a free lunch." An expression used on the Internet in e-mail, chat sessions, mailing lists, newsgroups, and other online forums. See also chat¹ (definition 1), e-mail¹ (definition 1), mailing list, newsgroup.

tap

n. A device that can be attached to an Ethernet bus to enable a computer to be connected.

tape

n. 1. A thin strip of polyester film coated with magnetic material that permits the recording of data. Because tape is a continuous length of data storage material and because the read/write head cannot "jump" to a desired point on the tape without the tape first being advanced to that point, tape must be read or written sequentially, not randomly (as can be done on a floppy disk or a hard disk). 2. A storage medium consisting of a thin strip of paper used to store information in the form of sequences of punched holes, chemical impregnation, or magnetic ink imprinting.

tape drive

n. A device for reading and writing tapes. See also tape (definition 1).

TAPI

n. Acronym for Telephony Application Programming Interface. In the Windows Open Systems Architecture (WOSA), a programming interface that gives Windows client applications access to a server's voice services. TAPI facilitates interoperability between personal computers and telephone equipment. Also called Telephony API. See also application programming interface, WOSA. Compare TSAPI.

target

n. Loosely, the objective of a computer command or operation. Examples are a computer that is to run a program translated for its use, a "foreign" language (for another computer) into which a program is to be translated, or a group of people for whom a particular product is designed. In MS-DOS usage, the target is often the disk referred to by prompts in a copy operation (for example, "insert target diskette"). In terms of the SCSI (small computer system interface) connection, the target is the device that receives commands. See also SCSI, target computer, target disk, target language.

task

n. A stand-alone application or a subprogram that is run as an independent entity.

taskbar

n. A graphic toolbar used in Windows 95 to select, via the mouse, one of a number of active applications. See also task button, toolbar.

task button

n. In Windows 95, a button that appears on the taskbar on the screen when an application is run. By clicking on the button, the user can switch from another application to the application corresponding to the button. See also taskbar.

T-carrier

n. A long-distance, digital communications line provided by a common carrier. Multiplexers at either end merge several voice channels and digital data streams for transmission and separate them when received. T-carrier service, introduced by AT&T in 1993, is defined at several capacity levels: T1, T2, T3, T4. In addition to voice communication, T-carriers are used for Internet connectivity. See also T1, T2, T3, T4.

TCP

n. Acronym for Transmission Control Protocol. The protocol within TCP/IP that governs the breakup of data messages into packets to be sent via IP, and the reassembly and verification of the complete messages from packets received by IP. TCP corresponds to the transport layer in the ISO/OSI model. See also ISO/OSI model, packet, TCP/IP. Compare IP.

TCP/IP

n. Acronym for Transmission Control Protocol/Internet Protocol. A protocol developed by the Department of Defense for communications between computers. It is built into the UNIX system and has become the de facto standard for data transmission over networks, including the Internet.

TCP/IP stack

n. The set of TCP/IP protocols. See also protocol stack, TCP/IP.

technical author

n. See tech writer.

technology

n. The application of science and engineering to the development of machines and procedures in order to enhance or improve human conditions, or at least to improve human efficiency in some respect. See also high tech.

technophile

n. One who is enthusiastic about emerging technology. Compare computerphile.

tech writer

n. Short for technical writer. One who writes the documentation material for a hardware or software product. Also called technical author. See also documentation.

telco

n. Short for telephone company. A term generally used in reference to a telephone company's provision of Internet services.

telecommunications

n. The transmission and reception of information of any type, including data, television pictures, sound, and facsimiles, using electrical or optical signals sent over wires or fibers or through the air.

telecommute

vb. To work in one location (often at home) and communicate with a main office at a different location through a personal computer equipped with a modem and communications software.

teleconferencing

n. The use of audio, video, or computer equipment linked through a communications system to enable geographically separated individuals to participate in a meeting or discussion. See also video conferencing.

telephony

n. Telephone technology; the conversion of sound into electrical signals, its transmission to another location, and its reconversion to sound, with or without the use of connecting wires.

telephony device

n. A mechanism designed to translate sound into electrical signals, transmit them, and then convert them back to sound.

telnet¹

n. A client program that implements the Telnet protocol.

telnet²

vb. To access a remote computer over the Internet using the Telnet protocol. See also telnet¹.

Telnet

n. A protocol that enables an Internet user to log on to and enter commands on a remote computer linked to the Internet, as if the user were using a text-based terminal directly attached to that computer. Telnet is part of the TCP/IP suite of protocols.

temp file

n. See temporary file.

template

n. 1. In an application package, an overlay for the keyboard that idenitfies special keys and key combinations. 2. In image processing, a pattern that can be used to identify or match a scanned image. 3. In spreadsheet programs, a predesigned spreadsheet that contains formulas, labels, and other elements. 4. In MS-DOS, a small portion of memory that holds the most recently typed MS-DOS command. 5. In word processing and desktop publishing programs, a predesigned document that contains formatting and, in many cases, generic text.

temporary file

n. A file created either in memory or on disk, by the operating system or some other program, to be used during a session and then discarded. Also called temp file. See also scratch¹.

tera-

prefix A prefix meaning 10¹²: 1 trillion in the American numbering system, 1 million million in British numbering. Abbreviated T. See also terabyte.

terabyte

n. A measurement used for high-capacity data storage. One terabyte equals 2⁴⁰, or 1,099,511,627,776, bytes, although it is commonly interpreted as simply one trillion bytes. Abbreviated TB.

terminal

n. 1. A device consisting of a video adapter, a monitor, and a keyboard. The adapter and monitor and, sometimes, the keyboard are usually combined in one unit. A terminal does little or no computer processing on its own; instead, it is connected to a computer with a communications link over a cable. Terminals are used primarily in multiuser systems and today are not often found on single-user personal computers. See also dumb terminal, smart terminal, terminal emulation. 2. In electronics, a point that can be physically linked to something else, usually by a wire, to form an electrical connection.

terminal emulation

n. The imitation of a terminal by using software that conforms to a standard, such as the ANSI standard for terminal emulation. Terminal-emulation software is used to make a microcomputer act as if it were a particular type of terminal while it is communicating with another computer, such as a mainframe. See also VT-52, VT-100, VT-200.

terminal server

n. In a local area network, a computer or controller that allows terminals, microcomputers, and other devices to connect to a network or host computer or to devices attached to that computer. See also controller, LAN, microcomputer, terminal.

terminate

vb. 1. With reference to software, to end a process or program. Abnormal termination occurs in response to user intervention or because of a hardware or software error. 2. With reference to hardware, to install a plug, jack, or other connector at the end of a wire or cable.

terminate-and-stay-resident program

n. See TSR.

terminator

n. 1. A character that indicates the end of a string, such as the null character in an ASCIIZ string. See also ASCII, ASCIIZ string. 2. An item of hardware that must be installed in the last device in a daisy chain or bus network, such as Ethernet or SCSI. See also terminator cap.

terminator cap

n. A special connector that must be attached to each end of an Ethernet bus. If one or both terminator caps are missing, the Ethernet network will not work.

test

vb. To check program correctness by trying out various sequences and input values. See also debug, test data.

text

n. 1. Data that consists of characters representing the words and symbols of human speech; usually, characters coded according to the ASCII standard, which assigns numeric values to numbers, letters, and certain symbols. 2. In word processing and desktop publishing, the main portion of a document, as opposed to headlines, tables, figures, footnotes, and other elements.

text box

n. In a dialog box or HTML form, a box in which the user may enter text.

text editor

n. See editor.

text file

n. A file composed of text characters. A text file can be a word-processing file or a "plain" ASCII file encoded in a format practically all computers can use. See also ASCII file, text (definition 1).

text mode

n. A display mode in which the monitor can display letters, numbers, and other text characters but no graphical images or WYSIWYG ("what-you-see-is-what-you-get") character formatting (italics, superscript, and so on). Also called alphanumeric mode, character mode. Compare graphics mode.

text-only file

n. See ASCII file.

TGA

n. 1. Short for Targa. A raster graphics file format from Truevision, Inc., that handles 16-, 24-, and 32-bit color. See also 16-bit color, 24-bit color, 32-bit color, raster graphics, video graphics board. 2. The brand name of a series of high-resolution video graphics boards.

The Microsoft Network

n. Microsoft Corporation's feature-rich online service, launched with the introduction of Windows 95 in August 1995. Acronym: MSN.

The World--Public Access UNIX

n. One of the oldest public access Internet service providers, based in Boston. In 1990, The World began offering full dial-up Internet access to the public. Other services include World Wide Web access, Usenet, SLIP/PPP support, telnet, FTP, IRC, Gopher, and e-mail. In 1995, The World began supporting local dial-up access via UUNET. See also ISP.

thin client

n. In a client/server architecture, a client computer that performs little or no data processing. The processing is instead performed by the server. See also client/server architecture, fat server, thin server. Compare fat client.

thin server

n. A client/server architecture in which most of an application is run on the client machine, which is called a fat client, with occasional data operations on a remote server. Such a configuration yields good client performance, but complicates administrative tasks, such as software upgrades. See also client/server architecture, fat client, thin client. Compare fat server.

third party

n. A company that manufactures and sells accessories or peripherals for use with a major manufacturer's computer or peripheral, usually without any involvement from the major manufacturer.

thrashing

n. The state of a virtual memory system that is spending almost all its time swapping pages in and out of memory rather than executing applications. See also swap (definition 2), virtual memory.

threaded discussion

n. In a newsgroup or other online forum, a series of messages or articles in which replies to an article are nested directly under it, instead of the articles being arranged in chronological or alphabetical order. See also newsgroup, thread (definition 3).

threaded newsreader

n. A newsreader that displays posts in newsgroups as threads. Replies to a post appear directly after the original post, rather than in chronological or any other order. See also newsreader, post, thread (definition 3).

three-tier client/server

n. A client/server architecture in which software systems are structured into three tiers or layers: the user interface layer, the business logic layer, and the database layer. Layers may have one or more components. For example, there can be one or more user interfaces in the top tier, each user interface may communicate with more than one application in the middle tier at the same time, and the applications in the middle tier may use more than one database at a time. Components in a tier may run on a computer that is separate from the other tiers, communicating with the other components over a network. See also client/server architecture. Compare two-tier client/server.

throttle control

n. A device that enables the user of a flight simulator or game to control simulated engine power. The throttle control is used along with a joystick (which controls the simulated ailerons and elevators) and possibly a rudder control.

throughput

n. A measure of the data transfer rate through a typically complex communications system or of the data processing rate in a computer system.

thumbnail

n. A small version of an image on a Web page or in a graphics cataloging program, usually containing a hyperlink to a full-size version of the image.

TIFF

or TIF n. Acronym for Tagged Image File Format or Tag Image File Format. A standard file format commonly used for scanning, storage, and interchange of gray-scale graphic images. TIFF may be the only format available for older programs (such as older versions of MacPaint), but most modern programs are able to save images in a variety of other formats, such as GIF or JPEG. See also gray scale. Compare GIF, JPEG.

time and date

n. In computing, the timekeeping and datekeeping functions maintained by the computer's operating system, used most visibly as a means of "stamping" files with the date and time of creation or last revision.

time out

or timeout or time-out n. An event that indicates that a predetermined amount of time has elapsed without some other expected event taking place. The time-out event is used to interrupt the process that had been waiting for the other expected event. For example, a dial-up remote system might allow the user 60 seconds to log in after making a connection. If the user fails to enter a valid login name and password within this time, the computer breaks the connection, thus protecting itself against crackers as well as freeing a phone line that may have gone dead.

TLA

n. Acronym for three-letter acronym. An ironic term, usually used in jest on the Internet in e-mail, newsgroups, and other online forums, referring to the large number of acronyms in computer terminology, particularly those consisting of three letters.

toggle²

vb. To switch back and forth between two states. For example, the Num Lock key on an IBM-style keyboard toggles the numeric keypad between numbers and cursor movement.

ToggleKeys

n. A feature of Windows 95 that sounds high and low beeps when one of the toggle keys (Caps Lock, Num Lock, or Scroll Lock) is turned on or off. See also typematic. Compare BounceKeys, FilterKeys, MouseKeys, ShowSounds, SoundSentry, StickyKeys, ToggleKeys.

token

n. 1. A unique structured data object or message that circulates continuously among the nodes of a token ring and describes the current state of the network. Before any node can send a message, it must first wait to control the token. See also token bus network, token passing, token ring network. 2. Any nonreducible textual element in data that is being parsed--for example, the use in a program of a variable name, a reserved word, or an operator. Storing tokens as short codes shortens program files and speeds execution. See also Basic, parse.

token bus network

n. A local area network formed in a bus topology (stations connected to a single, shared data highway) that uses token passing as a means of regulating traffic on the line. On a token bus network, a token governing the right to transmit is passed from one station to another, and each station holds the token for a brief time, during which it alone can transmit information. The token is transferred in order of priority from an "upstream" station to the next "downstream" station, which might or might not be the next station on the bus. In essence, the token "circles" through the network in a logical ring rather than a physical one. Token bus networks are defined in the IEEE 802.4 standards. See also bus network, IEEE 802 standards, token passing. Compare token ring network.

token passing

n. A method of controlling access on local area networks through the use of a special signal, called a token, that determines which station is allowed to transmit. The token, which is actually a short message, is passed from station to station around the network. Only the station with the token can transmit information. See also token bus network, token ring network. Compare collision detection, contention, CSMA/CD.

token ring network

n. A local area network formed in a ring (closed loop) topology that uses token passing as a means of regulating traffic on the line. On a token ring network, a token governing the right to transmit is passed from one station to the next in a physical circle. If a station has information to transmit, it "seizes" the token, marks it as being in use, and inserts the information. The "busy" token, plus message, is then passed around the circle, copied when it arrives at its destination, and eventually returned to the sender. The sender removes the attached message and then passes the freed token to the next station in line. Token ring networks are defined in the IEEE 802.5 standards. See also IEEE 802 standards, ring network, token passing. Compare token bus network.

Token Ring network

n. A token-passing, ring-shaped local area network developed by IBM that operates at 4 megabits (4 million bits) per second. With standard telephone wiring, the Token Ring network can connect up to 72 devices; with shielded twisted-pair (STP) wiring, the network supports up to 260 devices. Although it is based on a ring (closed loop) topology, the Token Ring network uses star-shaped clusters of up to eight workstations connected to a wiring concentrator (Multistation Access Unit, or MSAU), which, in turn, is connected to the main ring. The Token Ring network is designed to accommodate microcomputers, minicomputers, and mainframes; it follows the IEEE 802.5 standards for token ring networks. See also ring network, STP, token passing.

toner

n. Powdered pigment that is used in office copiers and in laser, LED, and LCD printers. See also electrophotographic printers.

toner cartridge

n. A disposable container that holds toner for a laser printer or other page printer. Some types of toner cartridge contain toner only; however, the most popular printer engines pack all expendables, including toner and the photosensitive drum, in a single cartridge. Toner cartridges are interchangeable among printers that use the same engine.

toolbar

n. In an application in a graphical user interface, a row, column, or block of on-screen buttons or icons. When these buttons or icons are clicked on with the mouse, macros or certain functions of the application are activated. For example, word processors often feature toolbars with buttons for changing text to italic, boldface, and other styles. Toolbars often can be customized by the user and usually can be moved around on the screen according to the user's preference. See also graphical user interface. Compare menu bar, palette (definition 1), taskbar, title bar.

toolbox

n. A set of predefined (and usually precompiled) routines a programmer can use in writing a program for a particular machine, environment, or application. Also called toolkit. See also library (definition 1).

Toolbox

n. A set of routines stored mostly in the read-only memory of a Macintosh that provide application programmers with the tools needed to support the graphical interface characteristic of the computer. Also called User Interface Toolbox.

ToolTips

n. In an application, notes that appear on the screen to provide information about a tool or a button on a toolbar. Compare ScreenTip.

topic drift

n. The tendency of an online discussion to move from its original subject to other related or unrelated directions. For example, someone in a conference devoted to television may ask about a news program; then somebody else may say something about a story on that program about food poisoning, which leads somebody else to start a general discussion on the advantages of organic fruits and vegetables.

topology

n. The configuration formed by the connections between devices on a local area network (LAN) or between two or more LANs. See also bus network, LAN, ring network, star network, token ring network, tree network.

touch screen

n. A computer screen designed or modified to recognize the location of a touch on its surface. By touching the screen, the user can make a selection or move a cursor. The simplest type of touch screen is made up of a grid of sensing lines, which determine the location of a touch by matching vertical and horizontal contacts. Another, more accurate type uses an electrically charged surface and sensors around the outer edges of the screen to detect the amount of electrical disruption and pinpoint exactly where contact has been made. A third type has infrared light-emitting diodes (LEDs) and sensors around the outer edges of the screen. These LEDs and sensors create an invisible infrared grid, which the user's finger interrupts, in front of the screen. Compare light pen.

tower

n. A microcomputer system in which the cabinet for the central processing unit (CPU) is tall, narrow, and deep rather than short, wide, and deep. The motherboard is usually vertical, and the disk drives are often perpendicular to the motherboard. A tower cabinet is at least 24 inches tall. See also cabinet, microcomputer, motherboard. Compare minitower.

trace

vb. To execute a program in such a way that the sequence of statements being executed can be observed. See also debugger, single step.

track¹

n. One of numerous circular data storage areas on a floppy disk or a hard drive, comparable to a groove on a record but not spiral. Tracks, composed of sectors, are recorded on a disk by an operating system during a disk format operation. On other storage media, such as tape, a track runs parallel to the edge of the medium.

trackball

n. A pointing device that consists of a ball resting on two rollers at right angles to each other, which translate the ball's motion into vertical and horizontal movement on the screen. A trackball also typically has one or more buttons to initiate other actions. A trackball's housing is stationary; its ball is rolled with the hand. Compare mechanical mouse.

trackpad

n. A pointing device consisting of a small, flat pad that is sensitive to touch. Users move the mouse cursor on screen by touching the trackpad and moving their fingers across the trackpad's surface. Such devices are most commonly installed on laptop computers. See also pointing device.

trademark

n. A word, phrase, symbol, or design (or some combination thereof) used to identify a proprietary product, often accompanied by the symbol or .

trade show

n. A multivendor sales event or exposition that showcases companies' products.

traditional newsgroup hierarchy

n. The seven standard newsgroup categories in Usenet: comp., misc., news., rec., sci., soc., and talk. Newsgroups can be added within the traditional hierarchy only following a formal voting process. See also comp. newsgroups, misc. newsgroups, newsgroup, news. newsgroups, rec. newsgroups, Request for Discussion, sci. newsgroups, soc. newsgroups, talk. newsgroups, Usenet. Compare alt. newsgroup.

traffic

n. The load carried by a communications link or channel.

train²

vb. To teach an end user how to use a software or hardware product.

transaction

n. A discrete activity within a computer system, such as an entry of a customer order or an update of an inventory item. Transactions are usually associated with database management, order entry, and other online systems.

transaction file

n. A file that contains the details of transactions, such as items and prices on invoices. It is used to update a master database file. See also transaction. Compare master file.

transceiver

n. Short for transmitter/receiver. A device that can both transmit and receive signals. On local area networks, a transceiver is the device that connects a computer to the network.

transceiver cable

n. A cable used to connect a host adapter within a computer to a local area network (LAN). See also AUI cable, LAN.

transfer

n. 1. The movement of data from one location to another. 2. The passing of program control from one portion of code to another.

transfer rate

n. The rate at which a circuit or a communications channel transfers information from source to destination, as over a network or to and from a disk drive. Transfer rate is measured in units of information per unit of time--for example, bits per second or characters per second--and can be measured either as a raw rate, which is the maximum transfer speed, or as an average rate, which includes gaps between blocks of data as part of the transmission time.

transfer time

n. The time elapsed between the start of a data transfer operation and its completion.

transistor

n. Short for transfer resistor. A solid-state circuit component, usually with three leads, in which a voltage or a current controls the flow of another current. The transistor can serve many functions, including those of amplifier, switch, and oscillator, and is a fundamental component of almost all modern electronics. See also base (definition 3), FET, NPN transistor, PNP transistor.

translate

vb. 1. In programming, to convert a program from one language to another. Translation is performed by special programs such as compilers, assemblers, and interpreters. 2. In computer graphics, to move an image in the "space" represented on the display, without turning (rotating) the image.

translated file

n. A file containing data that has been changed from binary (8-bit) format to ASCII (7-bit) format. BinHex and uuencode both translate binary files into ASCII. Such translation is necessary to transmit data through systems (such as e-mail) that may not preserve the eighth bit of each byte. A translated file must be decoded to its binary form before being used. See also BinHex, uuencode.

Transmission Control Protocol/Internet Protocol

n. See TCP/IP.

transmit

vb. To send information over a communications line or a circuit. Computer transmissions can take place in the following ways: k:\compdict\database\4359.doc

Transmit Data

n. See TXD.

transparent

adj. 1. In computer use, of, pertaining to, or characteristic of a device, function, or part of a program that works so smoothly and easily that it is invisible to the user. For example, the ability of one application to use files created by another is transparent if the user encounters no difficulty in opening, reading, or using the second program's files or does not even know the use is occurring. 2. In communications, of, pertaining to, or characteristic of a mode of transmission in which data can include any characters, including device-control characters, without the possibility of misinterpretation by the receiving station. For example, the receiving station will not end a transparent transmission until it receives a character in the data that indicates end of transmission. Thus, there is no danger of the receiving station ending communications prematurely. 3. In computer graphics, of, pertaining to, or characteristic of the lack of color in a particular region of an image so that the background color of the display shows through.

transport layer

n. The fourth of seven layers in the International Organization for Standardization's Open Systems Interconnection (OSI) model for standardizing computer-to-computer communications. The transport layer is one level above the network layer and is responsible for both quality of service and accurate delivery of information. Among the tasks performed on this layer are error detection and correction. See also ISO/OSI model.

transpose²

vb. 1. To reverse, as the order of the letters h and t in hte, in correcting the spelling of the; or reversing two wires in a circuit. 2. In mathematics and spreadsheets, to rotate a matrix (a rectangular array of numbers) about a diagonal axis.

tree

n. A data structure containing zero or more nodes that are linked together in a hierarchical fashion. If there are any nodes, one node is the root; each node except the root is the child of one and only one other node; and each node has zero or more nodes as children. See also child (definition 2), graph, leaf, node (definition 3), parent/child (definition 2), root.

tree search

n. A search procedure performed on a tree data structure. At each step of the search, a tree search is able to determine, by the value in a particular node, which branches of the tree to eliminate, without searching those branches themselves. See also branch (definition 1), tree structure.

trigger

n. In a database, an action that causes a procedure to be carried out automatically when a user attempts to modify data. A trigger can instruct the database system to take a specific action, depending on the particular change attempted. Incorrect, unwanted, or unauthorized changes can thereby be prevented, helping to maintain the integrity of the database.

Trojan horse

n. A destructive program disguised as a game, utility, or application. When run, a Trojan horse does something harmful to the computer system while appearing to do something useful. See also virus, worm.

troll

vb. To post a message in a newsgroup or other online conference in the hopes that somebody else will consider the original message so outrageous that it demands a heated reply. A classic example of trolling is an article in favor of torturing cats posted in a pet lovers' newsgroup. See also YHBT.

troubleshoot

vb. To isolate the source of a problem in a program, computer system, or network and remedy it.

true color

n. See 24-bit color.

TrueType

n. An outline font technology introduced by Apple Computer, Inc., in 1991 and by Microsoft Corporation in 1992 as a means of including high-grade fonts within the Apple Macintosh and Microsoft Windows operating systems. TrueType is a WYSIWYG font technology, which means that the printed output of TrueType fonts is identical to what appears on the screen. See also bitmapped font, outline font, PostScript.

truncate

vb. To cut off the beginning or end of a series of characters or numbers; specifically, to eliminate one or more of the least significant (typically rightmost) digits. In truncation, numbers are simply eliminated, unlike rounding, in which the rightmost digit might be incremented to preserve accuracy. Compare round.

TSR

n. Acronym for terminate-and-stay-resident. A program that remains loaded in memory even when it is not running, so that it can be quickly invoked for a specific task performed while another program is operating. Typically, these programs are used with operating systems that are not multitasking, such as MS-DOS. See also hot key.

TTFN

n. Acronym for "Ta ta for now." An expression sometimes used in Internet discussion groups, such as Internet Relay Chat (IRC), to signal a participant's temporary departure from the group. See also IRC.

TTL

n. See Time to Live, transistor-transistor logic.

TTY

n. Acronym for teletypewriter. A device for low-speed communications over a telephone line, consisting of a keyboard that sends a character code for each keystroke and a printer that prints characters as their codes are received. The simplest video display interface behaves like a TTY. See also KSR terminal, teletype mode.

tunnel

vb. To encapsulate or wrap a packet or a message from one protocol in the packet for another. The wrapped packet is then transmitted over a network via the protocol of the wrapper. This method of packet transmission is used to avoid protocol restrictions. See also communications protocol, packet (definition 2).

turnkey system

n. A finished system, complete with all necessary hardware and documentation and with software installed and ready to be used.

tutorial

n. A teaching aid designed to help people learn to use a product or procedure. In computer applications, a tutorial might be presented in either a book or a manual or as an interactive disk-based series of lessons provided with the program package.

TWAIN

n. Acronym for technology without an interesting name. The de facto standard interface between software applications and image-capturing devices such as a scanners. Nearly all scanners contain a TWAIN driver, but only TWAIN-compatible software can use the technology. See also scanner.

tweak

vb. To make final small changes to improve hardware or software performance; to fine-tune a nearly complete product.

twisted-pair cable

n. A cable made of two separately insulated strands of wire twisted together. It is used to reduce signal interference introduced by a strong radio source such as a nearby cable. One of the wires in the pair carries the sensitive signal, and the other wire is grounded.

two-dimensional

adj. Existing in reference to two measures, such as height and width--for example, a two-dimensional model drawn with reference to an x-axis and a y-axis, or a two-dimensional array of numbers placed in rows and columns. See also Cartesian coordinates.

two's complement

n. A number in the base-2 system (binary system) that is the true complement of another number. A two's complement is usually derived by reversing the digits in a binary number (changing 1s to 0s and 0s to 1s) and adding 1 to the result. When two's complements are used to represent negative numbers, the most significant (leftmost) digit is always 1. See also complement.

two-tier client/server

n. A client/server architecture in which software systems are structured into two tiers or layers: the user interface/business logic layer and the database layer. Fourth-generation languages (4GL) have helped to popularize the two-tier client/server architecture. Also called 4GL architecture. See also 4GL, client/server architecture. Compare three-tier client/server.

TXD

n. Short for Transmit (tx) Data. A line used to carry transmitted data from one device to another, as from computer to modem; in RS-232-C connections, pin 2. See also RS-232-C standard. Compare RXD.

type¹

n. 1. In programming, the nature of a variable--for example, integer, real number, text character, or floating-point number. Data types in programs are declared by the programmer and determine the range of values a variable can take as well as the operations that can be performed on it. See also data type. 2. In printing, the characters that make up printed text, the design of a set of characters (typeface), or, more loosely, the complete set of characters in a given size and style (font). See also font, typeface.

type²

vb. To enter information by means of the keyboard.

typeface

n. A specific, named design of a set of printed characters, such as Helvetica Bold Oblique, that has a specified obliqueness (degree of slant) and stroke weight (thickness of line). A typeface is not the same as a font, which is a specific size of a specific typeface, such as 12-point Helvetica Bold Oblique. Nor is a typeface the same as a typeface family, which is a group of related typefaces, such as the Helvetica family including Helvetica, Helvetica Bold, Helvetica Oblique, and Helvetica Bold Oblique. See also font.

type size

n. The size of printed characters, usually measured in points (a point is approximately ¹/₇₂ inch). See also point¹ (definition 1).

type style

n. 1. The obliqueness, or degree of slant, of a typeface. 2. Loosely, the overall design of a typeface or a typeface family. 3. One of the variant forms of a type character, including roman, bold, italic, and bold italic.

typography