Barrons Publishing Dictionary of Computer and Internet Terms 10th

rot13

416

Windows on a CD, and scan the installed Windows kernel to verify its authenticity.

Compare VIRUS. See also COMPUTER SECURITY; CRACKER; MALWARE.

rot13 (rotate 13) a type of ENCRYPTION commonly used on the Internet to conceal answers to puzzles and the like. To encode a message, the first 13 letters of the alphabet are swapped with the last 13. Performing the same swap again decodes the message. This is not a secure code, of course, but it provides a way to make things temporarily unreadable.

Qba’g lbh jbaqre jung guvf fnlf?

rotate in draw programs, to turn an object around a specific center. By default, the center of rotation is at the center of the object itself. You can drag this center to wherever you want it to be and then rotate the object around it. Rotation can be done interactively with the mouse, or if you require more precision, you can set the angle of rotation in degrees.

FIGURE 224. Rotate

ROTFL online abbreviation for “rolling on the floor laughing.” See also

ROFL.

round brackets the characters (), more properly called parentheses.

Contrast ANGLE BRACKETS; CURLY BRACKETS; SQUARE BRACKETS.

rounding the act of replacing a number with the nearest number that has a smaller number of significant digits. For example, 2.76 rounded to one decimal place is 2.8. The rule is that if the first digit to be discarded is 5 or greater, the last digit that is kept should be increased. Thus 2.74 → 2.7, but 2.76 → 2.8. Contrast TRUNCATION.

An alternative way to do rounding—easier on the computer—is to add 0.5 (or 0.05, or 0.005, etc.) to the number before discarding digits. For example:

2.74 + 0.05 = 2.79 → 2.7 2.76 + 0.05 = 2.81 → 2.8

The addition changes 7 to 8 in the desired cases; then the subsequent digits can simply be discarded.

In C and C++, you can round x to the nearest integer by evaluating floor(x+0.5), where floor finds the integer just below x. You can round x to two decimal places by evaluating floor(100*x+0.5)/100 (unless the result is thrown off by rounding error; see next entry).

417

RS-232

There is a big difference between rounding a number, which actually changes it, and simply printing it with a limited number of decimal places. In the latter case, the number itself is not changed, and its original value remains available for further computation.

rounding error an error that occurs because the computer cannot store the true value of most real numbers; instead, it can store only an approximation of a finite number of digits.

If you wish to write 1⁄3 as a decimal fraction, you can approximate it as 0.333333333, but it would require an infinite number of digits to express it exactly. The computer faces the same problem except that internally it stores the numbers in binary, and it can lose accuracy in converting between binary and decimal. For example, 0.1 has no exact representation on a computer; if you add the computer’s representation of 0.1 to 0 ten times, you will not get exactly 1. To avoid rounding error, some computer programs represent numbers as decimal digits. See

BINARY-CODED DECIMAL.

Route 128 a highway that skirts the west side of Boston, Massachusetts, passing through the cities of Needham and Waltham. Route 128 has been the home of a number of computer companies, including Digital Equipment Corporation and Lotus.

router a network component that joins several networks together intelligently. A router is often used to link an incoming DSL or cable modem connection to a home network. A router is more powerful than a bridge because instead of just choosing network segments based on previous traffic, a router can look up the best route to a distant site. The Internet relies heavily on routers. Compare BRIDGE; HUB; SWITCH (definition 2). See also DNS (definition 1).

RPG

1.abbreviation for role-playing game.

2.(Report Program Generator) a programming language developed by IBM in the 1960s in an attempt to simplify programming for business applications.

RPG was often the first programming language taught to trainees because RPG programming can be reduced to a fixed procedure for filling out forms. However, RPG programs are markedly less readable than programs in other languages, and complex algorithms are difficult to express in RPG.

RPM (revolutions per minute) a measure of speed of rotation. For example, many newer hard disks rotate at 10,000 RPM.

RPN see POLISH NOTATION.

RS-232 an Electronics Industries Association (EIA) recommended standard for transmitting serial data by wire. This standard is now officially known as EIA-232D. Computer serial ports follow the RS-232 standard.

RS-422, RS-423A			418
			TABLE 14
		RS-232 PIN CONNECTIONS (25-PIN)
		(Pin numbers are embossed on the connector.)
Pin	Signal	Direction	Explanation
1	GND	Both	Frame ground—ties together chassis of
			terminal and modem; often omitted.
2	TxD	To modem	Transmitted data.
3	RxD	To terminal	Received data.
4	RTS	To modem	Request to send—high when terminal
			is on and able to communicate.
5	CTS	To terminal	Clear to send—high when computer
			on other end is able to receive.
6	DSR	To terminal	Data set ready—high when modem is
			on and functioning.
7	SG	Both	Signal ground—reference point for all
			signal voltages.
8	CD	To terminal	Carrier detect—high when a connec-
			tion to another computer has been
			established.
20	DTR	To modem	Data terminal ready—high when
			terminal is on and functioning. Most
			modems hang up phone when DTR
			goes low.
22	RI	To terminal	Ring indicator—high when telephone
			is ringing.

RS-422, RS-423A two standards, recommended by the Electronics Industries Association (EIA), which define a format for transmitting serial data by wire, intended to replace the older RS-232 format. The new format offers faster data rates and greater immunity to electrical noise.

RS/6000 see WORKSTATION.

RSA encryption a public key encryption algorithm named after the initials of its developers (Ron Rivest, Adi Shamir, and Leonard Adleman). The security of the system relies on the difficulty of factoring very large numbers. More information about RSA encryption can be found at www.rsa.com. See also ENCRYPTION.

RSACi (Recreational Software Advisory Council on the Internet) the original web site content rating service, which became ICRA in 1999. See ICRA.

RSN Real Soon Now. (sarcastic) at an indefinite time in the future, probably much later than promised. See VAPORWARE.

RSS (Really Simple Syndication, or sometimes Rich Site Summary), a system that makes it easy to be notified of new information on web sites. The

CLONE TOOL.

419

run

RSS material comes from a special XML file on the web site, and the person who maintains the web site also updates that file when there is new material to announce. Blogs often make their content available this way. The original version of RSS was developed by Netscape in the late 1990s.

RTF (Rich Text Format) a format created by Microsoft for interchange of files between different word processing programs. RTF files consist of ASCII text with codes that indicate formatting and typefaces. For example,

{\rtf This is a {\b sample} of {\i RTF.}}

is RTF code for:

This is a sample of RTF.

RTF works somewhat like the lowest-level codes in TEX, but it is designed to be produced by programs, not humans. Many popular word processors can save their files in RTF. Compare TEX; contrast TEXT FILE.

RTFM (read the friendly manual) an exhortation to computer users who are unwilling to look things up for themselves. Compare RYFM.

rubber stamp a paint program tool that duplicates a selected area of a drawing. See the illustration at

Ruby a scripting language for object-oriented programming similar in intent to PERL and PYTHON. Ruby was developed by Yukihiro Matsumoto in 1995. See www.ruby-lang.org/en.

rule a procedure defined in advance that will automatically perform a particular action when a certain type of e-mail is received; for example, forwarding all messages from a particular person to another person, or moving all messages on a specific topic into the relevant folder.

ruler a strip at the top (and sometimes the side) of the on-screen work area, marked in units of measurement. Like its physical counterparts, an onscreen ruler is used to help you measure things. Rulers can be found in word processors, drawing programs, and page layout programs. You have the option to display the ruler, or to hide it and give yourself some more working room. You can also have the ruler show units of measurement other than inches (PICAs might be more useful for many applications). A ruler is especially useful when using a high degree of zoom because it helps you keep your orientation.

In a word processor, the ruler is used to set the TABs and MARGINs.

FIGURE 225. Ruler

run to make the computer execute a program. A distinction is often made between compile time (the time when the program is compiled; see COMPILER) and run time (the time when the program is run).

DATA COM-

run-length encoding

420

run-length encoding a way of storing data in less than the usual amount of space by using special codes to indicate repeated bytes. See

PRESSION.

run-time error an error that occurs when a program is being executed; an EXCEPTION. For example, a run-time error might occur if division by 0 is attempted or if the subscript for an array is outside the allowable bounds for that array. A run-time error may cause the program to stop execution, or it may be handled by an error-trapping routine (see TRAPPING).

Contrast COMPILE-TIME ERROR.

Run. . . a menu choice under Windows’s START BUTTON that allows you to run a program or open a file by typing its filename. For instance, to run myprog.exe from drive A, choose “Run. . . ” and type a:\myprog.exe or simply myprog (it isn’t necessary to type the extension). This is a common way to run setup programs when installing new software.

running head a small headline that appears at the top or bottom of each page. Running heads are usually there to remind the reader which chapter (or section) he or she is reading. In a dictionary like this one, the running heads tell you the first and last entries on the page spread.

RYFM (read your friendly manual, pronounced “riff-um”) Compare RTFM.

421	sans-serif

S

S (on a digital camera) shutter-priority autoexposure, the mode in which the user sets the shutter speed (exposure time) and the camera chooses the lens opening (f-ratio); same as TV. See F-RATIO. Contrast A; AV; P; TV.

Sad Mac (pre OS X only) the icon of a frowning Macintosh computer that announces the Mac has found a hardware problem and cannot finish booting.

Safari Apple Computer’s web browser for the Macintosh OS and Windows. The free download is available at www.apple.com/safari/download.

Compare FIREFOX; INTERNET EXPLORER; OPERA.

safe mode a way of running Windows with many special hardware drivers disabled, to work around problems with improperly installed hardware or software. Safe mode is used only for testing and to recover from an improper shutdown.

Samba a widely used, free, open-source software package for linking UNIX systems to Windows file and printer sharing, and for achieving various other kinds of interoperability between networks. For details, see www.samba.org. The name is derived from SMB (Server Message Block), an important part of the protocol that Samba follows. See CIFS; PROTOCOL.

sampling rate the number of times per second that sound waves are sampled and digitized. The highest frequency that can be reproduced is half the sampling rate. High-fidelity audio is usually sampled at 44.1 kHz (44,100 samples per second) in order to reproduce frequencies up to 22.05 kHz, just above the limit of human hearing. Speech can be stored more compactly by sampling at a lower rate, 22.05 or 11.025 kHz.

Another parameter is the number of bits of data stored in each sample. High-fidelity audio requires 16 bits per sample; speech can be reproduced adequately with 8 bits. One minute of sound, sampled at 44.1 kHz with 16 bits per sample, requires about 5 megabytes of disk space (10 megabytes for stereo). See also MP3.

SAN see STORAGE AREA NETWORK.

sandbox a safe environment to play in; a protective mechanism that prevents a program from accessing or changing memory or disk space outside of its own permitted area. This is a security feature preventing programs from damaging the system they run on. For example, a Java applet loaded from the World Wide Web runs in a sandbox where it is prohibited access to the hard disk on the browser’s computer.

sans-serif a typeface that does not have serifs, such as this one. Serifs are small perpendicular marks at the ends of the strokes (sans is French for “without”). See Figure 226. Contrast SERIF. See also TYPEFACE.

VECTOR PROCES-

FONT; VEC-

SAP

422

FIGURE 226. Sans-serif type

SAP a large developer of e-business software, headquartered in Walldorf, Germany. The name stands for the German words for “Systems, Applications, Products.” See www.sap.com.

SATA (serial ATA) a newer hardware implementation of the ATA hard disk interface, using serial data transmission through a narrow 7-pin connector, giving greater speed than PATA. SATA disk drives also have a new, narrow 15-pin power connector instead of the traditional 4-pin one. See

ATA. Compare ESATA; PATA.

saturation the intensity of a color. A highly saturated color is vivid and brilliant color; to dull a color (decrease its saturation), you add small amounts of its COMPLEMENT, making it closer to gray. See COLOR; HSB.

save to transfer information from the computer’s memory to a storage device such as a disk drive. Saving data is vital because the contents of the computer’s memory are lost when power is turned off. The opposite process is known as loading, retrieving, or opening.

Save As...

1.to save a document or drawing under a different name. The first time you save an untitled work, you will use “Save As . . . ” instead of “Save.”

2.to save a file in a different format (e.g., to save a CorelDraw file as a Windows Metafile). See also EXPORT.

SBC see SINGLE-BOARD COMPUTER.

scalable able to be used on a large or small scale without major changes. For example, much of the appeal of the UNIX operating system is its scalability; it can be used on small or large computers with little change in the way it works.

scalable font a font that can be used to print characters of any size. Most printers include scalable fonts; also, TrueType, OpenType, and Type 1 fonts are scalable. The shapes of the characters in a scalable font are stored in the form of vector graphics rather than bitmaps. See

TOR GRAPHICS.

scalar a quantity represented by a single number, as opposed to an ARRAY or LIST.

scalar processor a computer that operates on only one piece of data at a time. Most computers are scalar processors. Contrast

SOR. See also SUPERSCALAR PROCESSOR.

scale to change the size of a graphical object without changing its shape.

Contrast STRETCH.

423	scattergraph, scatter plot

FIGURE 227. Scale

ScanAlert a company that developed technology that could be used to verify that a web site has protection from hackers, and providing Hacker Safe certificates to web pages that passed the tests. However, it still is difficult to verify that a web page is truly safe. In 2008 ScanAlert was acquired by McAfee (web address: www.mcafee.com).

scanner

1. a device that enables a computer to read a printed or handwritten page. The simplest scanners give the contents of the page to the computer as a graphic image—a handy way of putting pictures into the computer (see DESKTOP PUBLISHING).

There are many nuances involved in scanning artwork. In some ways, it is quite similar to photography and if you are comfortable with a camera, it will make the transition to working with a scanner very smooth. Scanners can adjust the contrast and brightness of the image. Controls for setting the highlight and shadow area are usually provided. Color images can be color-corrected at the scanning stage.

With appropriate software, scanners can read the letters of typewritten text, transmitting them into the computer as if they were typed on the keyboard (OCR). This process, however, is seldom 100% accurate. You will find it necessary to proofread scanned copy very carefully.

2. Several other kinds of electronic devices are called scanners, including bar code readers (see BAR CODE) and devices for scanning the radio spectrum.

scattergraph, scatter plot a graph that shows points of data plotted on an x-y coordinate system. Also called an x-y graph.

FIGURE 228. Scattergraph

scientific notation

424

scientific notation see EXPONENTIAL NOTATION. scissors

1.a tool available in paint programs that allows you to define an area of the picture that you wish to separate from its surroundings. The resulting cutout may be resized (scaled), stretched, rotated, or moved.

The scissors tool is one of several SELECTION TOOLS available to you. Others include the LASSO, MAGIC WAND, and box selection tools. To save space, these tools may be grouped together in your toolbox and only one may be visible at a time.

2.icon for “cut the selected item to the Clipboard.” See also COPY; PASTE.

FIGURE 229. Scissors icon

SCO a software company that sued several companies claiming that it owned a copyright to part of the code in the open-source operating system Linux. Its claims were denied (SCO v. Novell).

SCR

1.(silicon controlled rectifier) an electronic component that functions as a latching switch for direct current. Compare TRANSISTOR.

Usage note: The hyphenation silicon-controlled rectifier is incorrect. The term means a controlled rectifier made of silicon, not a rectifier controlled by silicon.

2.(as a filename extension) screen saver. In Windows, an .scr file is just like an .exe file except that it can be installed as a screen saver; the assumption is that it will display graphics. A common way to trick people into running a malicious program is to give it the extension .scr, which they won’t recognize, instead of .exe. See EXE FILE; MALWARE.

scratch disk, scratch tape a disk or tape that one can erase and reuse at any time because it does not contain anything that needs to be kept for future use.

screen

1.a computer display; a monitor.

2.a screenful of information.

3.to process a grayscale image for printing by breaking down the various shades of gray into very small dots. See HALFTONE.

screen capture see SCREEN SHOT.

screen estate (informal) space on a computer screen, especially when thought of as a limited resource. A program that consumes too much screen estate will be hard to use concurrently with others. Compare REAL ESTATE.

425

scroll

screen saver a program that automatically blanks the screen of a computer, or displays a moving picture, when the computer has not been used for several minutes.

The original purpose of screen savers was to prevent “burn-in” (i.e., to keep the screen coating from wearing out in places where bright parts of the image were constantly displayed). Modern screens are less vulnerable to burn-in, and today, screen savers serve mainly to protect the privacy of users who are away from their desks, and to save energy when used in conjunction with monitors that turn themselves off when the screen goes blank. Screen savers also provide entertainment. See also

GREEN PC; ENERGY STAR.

screen shot, screen snapshot an image of the current screen, saved as a bitmap.

Snapshots of the screen are easy to obtain: on the Macintosh, hold down Command and Shift, then press 3. This places a bitmapped image of the screen in a PICT file in your root directory. In Windows, pressing the Print Screen key puts a copy of the entire screen onto the CLIPBOARD. Holding down Alt while pressing Print Screen saves a bitmap of the active window only.

script

1.a style of type that resembles cursive handwriting (not italics), as shown in Figure 230.

2.a file containing commands to be executed, such as a SHELL SCRIPT or a script of dialing commands for a communication program. See also

JAVASCRIPT; VBSCRIPT; PERL; PYTHON; CGI.

3. a file or printout containing a copy of information that was displayed on the screen.

FIGURE 230. Script type

scroll

1.to move information across the screen as if the screen were a window or porthole through which you are looking. For example, all word processing programs can scroll vertically, and some can also scroll horizontally.

2.(slang) to type gibberish rapidly and repeatedly in order to disrupt a discussion in a chat room. (This makes all the real messages scroll by too fast for people to read them.) See CHAT ROOM.