Barrons Publishing Dictionary of Computer and Internet Terms 10th
.pdf
switched line |
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switched line an ordinary (POTS) telephone line on which you establish connections by dialing; the path actually taken by the signals need not be the same when you call the same number twice on different occasions. Contrast DSL; T1 LINE; T3 LINE.
switching power supply a power supply that regulates the voltage of direct current by switching it off and on very rapidly and then smoothing out the variations. Most computer power supplies are of this type. The advantages of a switching power supply are that it does not waste energy and does not require a heavy transformer, since the incoming AC is chopped to give a high frequency that can be handled by a smaller, lighter transformer. The disadvantage is that it produces radio-frequency interference. See POWER SUPPLY; RFI PROTECTION.
SWMBO online abbreviation for “She Who Must Be Obeyed.” Used facetiously to refer to one’s wife in imitation of Rumpole, the eccentric and somewhat henpecked lawyer in stories by John Clifford Mortimer.
SXGA (Super XGA) a monitor resolution of 1280 × 1024 pixels.
symbol font a font containing symbols or ornaments rather than a regular alphabet. Also called a pi font or DINGBATS.
FIGURE 255. Symbol font (Minion Ornaments)
symbolic algebra the manipulation of mathematical symbols (not just their numerical values). For example, we can calculate that (a + b) × (c + d) = ac + ad + bc + bd without knowing the values of a, b, c, or d.
Symbolic algebra on computers began with the MACSYMA project at MIT in the 1960s. Today, popular symbolic algebra programs for personal computers include MathCad, Maple, Mathematica, and MATLAB. They greatly simplify the formerly tedious process of deriving and manipulating mathematical formulas.
symbolic debugger program that lets you step through a compiled program, interrupting it at any point and examining or changing the values of variables.
“Symbolic” means that programmer-assigned names in the program are recognized. A symbolic debugger analyzes the source code and the object code together, so that even though the program has been compiled, you can work with it as if you were editing the source program.
symbolic programming a kind of programming in which variables can stand for pieces of the program itself (symbolic expressions), not just
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systems programmer |
numbers, strings, or other values. Lisp and Prolog are examples of symbolic programming languages. See LISP; PROLOG; SYMBOLIC ALGEBRA.
sync pulse the part of a video signal that indicates when the electron beam should scan each line. See SYNCHRONIZATION.
synchronization
1.the act of making a video display scan each line at exactly the right time, so that the image is displayed correctly. The input to a monitor consists of SYNC PULSEs as well as red, green, and blue video.
2.the process of keeping two or more disk drives up to date relative to each other, by copying the latest version of each file to each device. This is a practical problem if you work with more than one computer, such as a laptop and a desktop machine. The Briefcase feature of Windows helps users synchronize files.
synchronous occurring in unison with a separate signal. In synchronous data transmission, there are two signals, data and clock. The clock signal indicates exactly when the data line should be read in order to obtain each successive bit. Contrast ASYNCHRONOUS.
syntax the set of rules that specify how the symbols of a language can be put together to form meaningful statements. A syntax error is a place in a program where the syntax rules of the programming language were not followed.
syntax diagram a diagram showing how to arrange elements of a language. For an example see RAILROAD DIAGRAM.
synthesizer
1. a device or program for generating speech sounds by computer. See
SPEECH SYNTHESIS.
2. a device for generating musical sounds by computer, usually from MIDI data. See MIDI.
Sys Req key the key on IBM mainframe terminals that enables the user to communicate with the communications system itself rather than the application program. The IBM PC AT and all subsequent PCs have a Sys Req key, but little or no software makes use of it.
sysadmin (system administrator) a person who manages a multiuser computer.
systems programmer person who writes the programs needed for a computer system to function (as opposed to the programs that do particular kinds of useful computation). Some of the programs that systems programmers write include operating systems, language processors and compilers, and data file management programs. Systems programming requires considerable knowledge of the particular computer system being used. Contrast APPLICATIONS PROGRAMMER.
T1 line |
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T
T1 line a special type of telephone line for digital communication only, with a maximum data rate of 1.544 million bits per second. Many Internet sites are connected to each other through T1 lines. Contrast DSL;
ISDN; SWITCHED LINE; T3 LINE.
T3 line a high-speed digital telephone line with a maximum data rate of 45 million bits per second, 28 times that of a T1 line. Larger Internet sites use T3 lines to link to each other. Contrast DSL; ISDN; SWITCHED LINE; T1 LINE.
tab a visual indication of multiple pages in a dialog box (Figure 256). Click on the appropriately labeled tab to get to the desired page.
FIGURE 256. Tabs in dialog box
Tab the key on a computer keyboard that is marked with forward and backward arrows (Figure 257). (From tabulator, a mechanical device for lining up columns on a typewriter.)
The Tab key advances the cursor to a preset spot; Shift-Tab goes back to the previous tab stop. Most word processors and page layout programs let you set the TAB STOPS where you want them and otherwise provide a reasonable set of defaults, usually every half inch or so.
Always use the Tab key instead of the space bar to align type. When setting proportional type, it is impossible to get columns to line up by adding space characters; you must set the tabs.
The Tab key has ASCII code 9 and is equivalent to Ctrl-I. The backward Tab (Shift-Tab) key has no ASCII code.
When entering text into a dialog box, the Tab key often moves the cursor from one field to the next.
FIGURE 257. Tab key
tab-delimited separated by the Tab character (ASCII 9). A tab-delimited file is a text file in which data items are separated by Tab characters, which will usually cause the items to line up in columns when viewed in an edi-
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table, HTML |
tor, although different editors place the columns differently. This is one way of saving the contents of a spreadsheet to a text file that can be read back in without losing the arrangement of the items. Compare CSV FILE.
tab stops adjustable markers that indicate the next horizontal position of the cursor when the Tab key is pressed. See Figure 258.
FIGURE 258. Tab stops
tabbed browsing the ability to open more than one page simultaneously in a web browser, with each page appearing as a tab on the screen allowing the user to quickly switch between them.
table an arrangement of data in a database where each row defines a relationship between the items in that row. See RELATIONAL DATABASE.
FIGURE 259. Table (in HTML)
table, HTML a set of tabular information displayed with special HTML tags. Here is an example:
tag |
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<HTML><HEAD><TITLE>Table Example</TITLE></HEAD> <BODY>
<H2> HTML Table Example</H2> <TABLE BORDER>
<TR><TD>President</TD><TD>Years in Office</TD> <TD>Home State</TD></TR>
<TR><TD>George Washington</TD><TD>1789-1797</TD> <TD>Virginia</TD></TR>
<TR><TD>John Adams</TD><TD>1797-1801</TD> <TD>Massachusetts</TD></TR>
<TR><TD>Thomas Jefferson</TD><TD>1801-1809</TD> <TD>Virginia</TD></TR>
</TABLE>
</BODY></HTML>
The BORDER attribute automatically sets up a border for the table; the border can be set wider by specifying its width in pixels (BORDER=3). If no border is desired, simply delete the BORDER attribute.
Each row of the table is enclosed between the <TR> and </TR> tags, and each data item in the table is enclosed between <TD> and </TD> tags. The web browser will automatically line up the items correctly; it doesn’t matter where the line breaks in the HTML code occur. Figure 259 shows how this table is displayed.
The table elements do not have to be text; they can also include graphic images and links. Many web designers use tables with invisible borders to organize and align elements of a web page.
tag a code inserted into a FILE or data structure indicating how something is to be interpreted. Many pieces of software use tags of various kinds for various purposes. HTML commands are often called tags. See DATA STRUCTURES; HTML.
talent (digital video) hired human actors or voice actors, as opposed to computer-generated characters. Contrast ACTOR.
tall paper orientation that is taller than it is wide; also called PORTRAIT or VERTICAL orientation.
tan the trigonometric tangent function.
If A is an angle in a right triangle, then the tangent of A (written as tan A) is defined to be
length of opposite side
tan A = length of adjacent side
The function tan(A) in many programming languages calculates the value of tan A, with A in radians. See TRIGONOMETRIC FUNCTIONS for an illustration.
tangent
1.a line that just touches a circle or other curve.
2.the trigonometric tangent function. See TRIGONOMETRIC FUNCTIONS.
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taskbar |
tape a thin, flexible plastic material with a magnetic coating on which data can be stored. In the 1970s, tape was a common alternative to disks as a way for computers to store files. Today, tapes are still used for backups. Tapes are much slower than disks; writing a large backup to tape can take hours.
tape drive a device that enables a computer to read and write magnetic tape.
tar file in UNIX, a collection of files made into one file with the tar (tape archive) program. (Nowadays, tar files are almost always stored on disk, not tape.) To extract the contents of a tar file, use the command:
% tar -xvf filename.tar
Unlike ZIP, tar does not compress files; thus, tar files are often compressed with another utility (such as compress, which adds .Z at the end of the filename). See ZIP FILE.
target
1.the place to which information is copied (e.g., the “target disk” when copying disks); the opposite of source.
2.something that is being searched for (as when searching for a word in a document).
3.The target attribute in an HTML link can be used to specify where the result of the link will appear. Here is an example where the linked web page will appear in a new window:
<a href=”test2.htm” target=”_blank”>link to test2</a>
task a PROCESS; one of several computer programs that are executing concurrently.
Task Manager a Windows utility that shows a list of running programs and operating system tasks and allows you to terminate them. You can access it at any time by pressing Ctrl-Alt-Del or by typing taskmgr at a command prompt.
To find out the function of any task, especially if you are concerned that it might be MALWARE, simply search for its name on GOOGLE or another large search engine.
taskbar the area at the bottom of the screen in Windows, containing the START BUTTON and a button for every program that is currently running. It also contains tiny icons for the speaker (volume control), clock, printer (if printing), fax modem (if active), and other specialized programs.
The taskbar is normally wide enough for one row of buttons, but you can widen it, shrink it, or move it to a different edge of the screen by dragging it with the mouse. If you can’t see the taskbar, look closely to see whether it has been reduced to minimum width or moved to an unusual location.
TB |
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FIGURE 260. Taskbar (Windows)
TB terabyte.
TCL/TK (Tool Command Language and [graphical] Tool Kit) a programming language developed by John Ousterhout in the tradition of Perl and Awk. As its name suggests, TCL/TK is for building customized tools. It links together pre-existing software and system facilities, including network communication, along with new code to generate easy-to-use programs with a graphical user interface. It is one of the easiest ways to do GUI programming under UNIX, and implementations for Microsoft Windows also exist. TCL/TK is an open-source project, and most implementations of it are distributed free of charge. For more information, see www.scriptics.com.
TCO (total cost of ownership) the complete cost of owning and using a machine during its useful life, including not only the cost of the machine itself, but also maintenance, repairs, and consumable supplies such as ink and paper.
A low-cost inkjet printer can have higher TCO, in the long run, than an expensive laser printer if its ink cartridges and special paper are relatively expensive.
TCP/IP (Transmission Control Protocol/Internet Protocol) a standard format for transmitting data in packets from one computer to another. It is used on the Internet and various other networks. The two parts of TCP/IP are TCP, which deals with construction of data packets, and IP, which routes them from machine to machine. See INTERNET; WIDE-AREA NETWORK.
teh a common typing error for the that has been adopted as a deliberately comical spelling. See LEETSPEAK.
telecommute to work at a job from a home office with the aid of a computer, modem, telephone, fax, and other specialized equipment.
telecompute to use the computer facilities at another location by using a or a modem link.
Telnet a protocol for using one computer as a terminal on another; only textual communication is supported, not graphics. Telnet is widely used to access UNIX systems remotely. To use it, type telnet or tn at a command prompt, or type a URL such as telnet:abc.xyz.com into your browser. See also RLOGIN; TCP/IP.
template a pattern for arranging or matching things:
1.a plastic card with shapes cut out of it. A programmer using a template card can easily trace out the symbols that are needed in drawing a flowchart.
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TeX |
2.a particular pattern for a spreadsheet program, a database program, or page layout program that is frequently used. Therefore, storing the template will save you from having to retype the specifications each time.
3.a regular expression or other pattern to be matched. See REGULAR
EXPRESSION.
ter Latin for “a third time,” used to denote revised CCITT and ITU-T standards. See CCITT; ITU-T.
tera- metric prefix meaning ×1,000,000,000,000 (1012) or, in rating computer memories and disks, ×1,099,511,627,776 (= 10244). Tera- is derived from the Greek word for monster or freak. See METRIC PREFIXES.
terabyte an amount of storage capacity equal to 1000 or 1024 gigabytes.
See GIGABYTE; METRIC PREFIXES.
Teragrid a GRID COMPUTING system organized by the National Science Foundation for solving computationally complicated scientific problems. See www.teragrid.org.
terminal an input-output device consisting of a screen and keyboard for communicating with a computer.
The earliest terminals were teletype machines. Today, personal computers are sometimes used as terminals on larger computers. See DATA COMMUNICATION; DOWNLOAD; MODEM; REMOTE DESKTOP; TELNET; UPLOAD.
terminal-node controller see PACKET RADIO.
Terminal Services the subsystem of Windows that supports REMOTE DESKTOP and TELNET access from other computers. See REMOTE DESKTOP; TS-CAL.
terminator a connector containing resistors to absorb reflected signals in a cable. Terminators are usually required on SCSI cables and on coaxial network cables.
TeX (pronounced “tekh”) a computer typesetting program used by the American Mathematical Society and many book publishers and educational institutions. TEX was designed and first implemented by D. E. Knuth of Stanford University. It was used to typeset this book.
Unlike most desktop publishing systems, TEX does not attempt to show you the appearance of the finished document on the screen as you edit it (though screen previews can be generated). Instead, you type a document with codes in it that indicate boldface, italics, special characters (e.g., \int for an integral sign), and the like (Table 15).
The rationale is that correct typesetting relies on distinctions that are too subtle to see on a computer screen. A user who wants an em dash rather than an en dash should say so with explicit codes rather than trying to make a mark that appears the right length on the screen. Likewise, large-scale aspects of design should be automated; you should be able
Texas Instruments |
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just to give the title of a chapter, and let the computer take care of numbering the chapter and putting the title in the right place on the page.
Most TEX users access TEX through LATEX, a package of ready-to-use document designs and command shortcuts that make the system easier to use. See LATEX.
TEX is generally considered the most sophisticated computer typesetting system, as well as (for an experienced user) one of the easiest to use. It sets a standard that other desktop publishing systems try to emulate.
Usage note: The logo TEXis easily produced from within TEXor LATEX. Otherwise, it is usually typed “TeX.”
TABLE 15
TEXNOTATIONS USED IN MATHEMATICAL FORMULAS
∞\infty
±\pm
×\times
÷\div
′^\prime
° |
^\circ |
≤ |
\leq |
≥\geq
\in
\subset
\subseteq
→\rightarrow
\Rightarrow
α, β |
\alpha, |
\beta |
(etc.) |
||
Γ, |
\Gamma, |
\Delta |
(etc.) |
||
abcd |
a^{bcd} |
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abcd |
a_{bcd} |
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xyz |
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{xyz}\over{abc} |
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abc |
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xyz |
\sqrt{xyz} |
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n |
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∑ ai |
\sum_{i=1}^{n} |
a_{i} |
||
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i=1 |
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∫ab f (x)dx |
\int_{a}^{b} f(x) dx |
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Texas Instruments (TI) a manufacturer of semiconductors and computers, headquartered in Dallas, Texas. Jack S. Kilby developed the first working integrated circuit (“silicon chip”) at TI in 1958, making it possible to miniaturize electronic equipment to a degree far beyond earlier expectations. Currently, TI produces computers, calculators, and a wide variety of related components and other electronic devices. Web address: www.ti.com.
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third party |
text box an area within a window where the user can type or edit characters.
FIGURE 261. Text box
text editor an editor for text files. See EDITOR.
text file a file containing only characters (in ASCII, ANSI, EBCDIC, or Unicode) plus end of line marks (see CR, LF), without any way of indicating the style, size, or color of type or any other special effects. In Windows, the Notepad program is an editor for ANSI (extended ASCII) and Unicode text files. Contrast RICH TEXT.
text to columns a procedure to split the data currently in a single spreadsheet column so that it spans adjacent columns. For example, if the text “100, 200” appears in column A, then splitting the text using the comma as the delimiter will put “100” in column A and “200” in column B. This feature is particularly helpful when pasting data off a web page into a spreadsheet.
text wrap see REFLOW; WORD WRAP.
texture mapping the act of applying a texture to the surface of a 3D wireframe model.
thermal printer a printer that prints by heating spots on the paper with an array of tiny, fast-acting heating elements. Thermal printers are among the least expensive printers and are often used in calculators and point- of-sale terminals. They require special paper that may discolor with age.
thickwire the thicker type of Ethernet coaxial cable. See 10BASE-5.
thin client a computer terminal with some computational power built in; a networked computer that relies on the server not only to store files, but also to do nearly all the computing while the client manages the graphical user interface. See TERMINAL. Contrast DISKLESS WORKSTATION, which does its own computing.
thinking outside the box (jargon) thinking outside presumed limits; thinking creatively.
thinnet thinwire Ethernet. See 10BASE-2; ETHERNET.
thinwire the thinner type of Ethernet coaxial cable. See 10BASE-2.
third-generation computers the first generation of computers made with integrated circuits.
third party someone other than the maker of a machine and the END USER. For example, third-party software is software that does not come from the manufacturer of the computer, nor is it developed by the user. Most software today is third-party software.