Dictionary of Computer and Internet Terms phần 5 pps

FIGURE 122. Graphics tablet (Photo courtesy of Wacom Technology) grayscale 1. a series of boxes filled with a range of black tints from pure white to 100% black. A grayscale is used to test a printer, monitor, scanner, or printing press. 2. (scanner terminology) the range of grays in an image as measured by the scanner. 3. a description of any image that contains shades of gray as well as black and white. Greek the alphabet used in ancient and modern Greece, Α Β Γ Δ Ω and α β ’’ γ δ ω. Greek letters are often used as mathematical symbols. For the complete Greek alphabet, see page 6. Contrast CYRILLIC; LATIN. greeking the use of random letters or marks to show the overall appearance of a printed page without showing the actual text. With computers, greeking is used when the page is displayed too small for the text to be readable on the screen. FIGURE 123. Greeking Green Book the Philips/Sony standard for multimedia interactive compact discs (not including personal computer software). Green PC a personal computer that draws little electrical power when idle, even though still turned on. A Green PC typically stops spinning its hard 219 Green PC 7_4105_DO_CompInternetTerms_G 12/29/08 10:25 AM Page 219 disk and shuts down power to the monitor if several minutes elapse with no keyboard activity. See also ENERGY STAR. Gregorian calendar the calendar system presently in use, introduced by Pope Gregory in 1582 and adopted in England in 1752 and in Russia in 1918. It is exactly like the Julian calendar except that years divisible by 100 are not leap years unless they are also divisible by 400. The Gregorian calendar thus follows the earth’s revolution around the sun more accurately than the Julian calendar did. See LEAP YEAR. grep the UNIX command that reads a text file and outputs all the lines that contain a particular series of characters. For example, the command grep abc myfile reads the file myfile and outputs every line that contains “abc.” Instead of specifying the exact characters to be searched for, you can give a regular expression that defines them. For example, grep [bB]ill myfile outputs all the lines that contain either “bill” or “Bill.” See REGULAR EXPRESSION. The origin of the word grep is disputed, but it may be an abbreviated editing command, g/re/p, where re stands for “regular expression,” g means “global search,” and p means “print” (i.e., display all lines that match the search criteria). Grep programs have been written for other operating systems, such as Windows. Compare FIND. grid a feature of various draw programs and paint programs that allows lines to be drawn only in certain positions, as if they were drawn on the lines of graph paper. The grid makes it much easier to draw parallel and perpendicular lines, lay out diagrams, and avoid irregular breaks. However, when the grid is turned on, there are positions in which you cannot draw. See also DRAW PROGRAM; PAINT PROGRAM. grid computing the process of solving computationally complicated prob- lems by distributing parts of the problem to unused capacity on a widely dispersed set of machines that are connected to the Internet. For examples, see SETI@HOME; TERAGRID; and www.grid.org. For con- trast, see CLUSTER COMPUTING. grid system a way of standardizing the layout of many related pages, such as the pages of a multipage document. The designer first draws a grid that will define the possible positions of columns, horizontal divisions, and pictures. Not all the possibilities of the grid are used on any single page, but the grid ensures that column positions do not vary haphazardly, and thereby makes the pages look related. griefer (slang) a person who plays a multiplayer game or participates in other online group activities for the purpose of making other people mis- erable. Griefers do not play to win; they do not defeat their opponents Gregorian calendar 220 7_4105_DO_CompInternetTerms_G 12/29/08 10:25 AM Page 220 fairly. They play to lose, and they dish out insults, misinformation, and harassment in the process. Grokster a file sharing service found liable for inducing its users to violate copyright law, in the case Metro-Goldwyn-Mayer Studios et al. v. Grokster (545 U.S. 913 (2005)), decided by the Supreme Court in 2005. See also NAPSTER. gross megapixels the total number of megapixels on an image sensor, whether or not all of them are actually used in taking pictures. Contrast EFFECTIVE MEGAPIXELS. grounding the establishment of a uniform reference voltage level across several pieces of electrical equipment that are connected together. In any electrical device, “ground level” is the voltage level to which all other voltages are compared. In most computers, the ground level is connected to the ground pin (the third, rounded pin) of the power plug, and the power line then connects it to the earth itself, thereby assuring that the ground level for all machines is the same. This helps prevent cables from picking up noise or emitting radio-frequency interference. It also reduces the danger of damage from lightning. See ELECTRONIC CIR- CUIT DIAGRAM SYMBOLS; POWER LINE PROTECTION; RFI PROTECTION. groupware software that makes it easy for a group of people to work on the same data through a network, by facilitating file sharing and other forms of communication. Lotus Notes is an example of widely used groupware. GTG chat-room abbreviation for “[I’ve] got to go.” gTLD (generic Top Level Domain) an identifier such as .com or .edu at the end of a U.S. web address; see www.iana.org/domains/root/db/# for the complete list of possibilities. See also CCTLD; TLD. GUI see GRAPHICAL USER INTERFACE. GUID (Globally Unique Identifier) a 128-bit number used by Microsoft WINDOWS to identify a user, software component, or other entity. GUIDs are most often written as groups of hexadecimal digits in braces, such as: {79376820-07D0-11CF-A24D-0020AFD79767} Windows includes an algorithm to generate GUIDs based on an encrypted version of the user’s MAC ADDRESS, which in turn is guaranteed to be unique. (See MAC ADDRESS.) Thus, anyone running Windows who has an Ethernet adapter can create GUIDs that are known to be unique in the entire world. Computers without an Ethernet adapter can generate GUIDs that are likely to be unique but not guaranteed to be. guideline a nonprinting line that aids in aligning text and other objects in a draw program or page layout program. Some programs allow you to turn 221 guideline 7_4105_DO_CompInternetTerms_G 12/29/08 10:25 AM Page 221 on a snap-to-guidelines feature that causes the guidelines and objects to have a magnetic attraction for each other. See also SNAP-TO-GRID. guiltware persistent NAGWARE; software that repeatedly asks for a mone- tary contribution and tries to make you feel guilty if you don’t pay. Contrast CAREWARE; FREEWARE. gunk (slang) any undesirable thing that degrades the performance of a computer, such as physical dust, obsolete software, or spyware. Gunk includes well-intentioned utilities that waste CPU time constantly mon- itoring the status of a modem, network card, or disk drive, as well as VIRUSES, ADWARE, and other MALWARE. gutter the blank space between columns of type or between pages of a book. guiltware 222 7_4105_DO_CompInternetTerms_G 12/29/08 10:25 AM Page 222 H h4x LEETSPEAK for “hacks.” See HACK, especially definition 4. hack 1. to modify, especially in an improvised way: “This version of the pro- gram has been hacked to run under UNIX instead of Windows.” 2. to program a computer, either tediously or enthusiastically: “We spent the whole night hacking.” 3. to break into a computer system or otherwise do mischief: “We’ve been hacked.” See also ETHICAL HACKING. 4. a clever programming technique: “This hack enables a console-mode program to change the title bar of its window.” When someone in an online game is accused of “hacks,” it means that he or she is suspected of using software bugs or a third-party program to achieve results that the game designers did not intend. hack attack (slang) a sudden inspiration or compulsion to work on a com- puter program. Despite what it sounds like, a “hack attack” has nothing to do with computer security violations. hacker 1. an exceptionally skilled computer programmer. 2. a person who programs computers for recreation or as a hobby. 3. a person who “breaks into” computers without authorization, either for malicious reasons or just to prove it can be done; a CRACKER. See 2600; COMPUTER SECURITY. hacker ethic the value system of computer enthusiasts who believe in help- ing each other advance technology by sharing knowledge without imme- diate concern for making money. See HACKER (definition 2). The hacker ethic has led to valuable cooperative projects such as GNU, LINUX, TEX, USENET, and the INTERNET. Usage note: The term hacker ethic is sometimes misappropriated by malicious individuals who believe they are somehow exempt from ordi- nary rules of ethics (see HACKER, definition 3). In its proper sense, the hacker ethic is an extension of ordinary ethics, not an exemption or loop- hole. Hacker Safe see SCANALTERT. hackish (slang) pertaining to the culture of HACKERs (definitions 1 and 2 and sometimes 3). For instance, using binary numbers on a birthday cake is a hackish thing to do. hafnium chemical element (atomic number 72) used as an insulator in inte- grated circuit transistors. 223 hafnium 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 223 hairline a very thin line, usually about .003 inch wide. FIGURE 124. Hairline and other line widths HAL 1. in Windows NT and its derivatives, the Hardware Abstraction Layer, the component of the operating system responsible for low-level inter- action with the CPU and closely related hardware. 2. the fictional computer in the movie 2001: A Space Odyssey (1968). Replace each letter of HAL with the next letter in the alphabet to see an amusing coincidence. half adder a logic circuit that adds two one-digit binary numbers, produc- ing two digits of output. See BINARY ADDITION. half duplex communication in two directions, but not at the same time. For instance, a two-way radio with a push-to-talk switch is a half duplex device; you cannot hear the other person while you are talking. Contrast FULL DUPLEX. halftone the reproduction of a continuous-tone image (containing shades of gray or colors) by converting it into a pattern of very small dots of vari- ous sizes. (For an example, look closely at a picture in a newspaper or magazine.) Laser printers and printing presses can print shades of gray only as halftones. See also GRAYSCALE; PHOTOGRAPH. FIGURE 125. Halftone image (enlarged) halting problem the problem of determining whether a particular computer program will terminate or will continue forever in an endless loop; a famous theoretical result in computer science. Consider a computer program A that analyzes other programs; call the analyzed program B. Suppose A can always determine, with complete hairline 224 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 224 225 hard-coded certainty, whether B will ever terminate. You could arrange for A to repeat endlessly if it finds that B terminates, and terminate if it finds that B repeats endlessly. You could then feed A a copy of itself (i.e., let B = A), and you’d have a program that terminates if and only if it does not terminate. This is a contradiction, proving that A, as described, cannot exist. hand tool a tool available in some graphical environments that looks like a human hand and allows you to move the picture around the screen. If there is a hand tool provided, there will usually not be a SCROLL BAR at the side and bottom of the viewing window. handle 1. a nickname used in online communication. 2. in Windows systems programming, a POINTER to a window or other system resource. 3. (in programs with a graphical user interface) the little black boxes at the corners and midpoints of an object that has been selected for editing. As the name suggests, handles give you a place to “grab” onto an object with the mouse and manipulate it. Dragging a corner handle (any one of the four) will change the size of the object. Dragging a midpoint handle will stretch or shrink the object in one dimension. FIGURE 126. Handles (definition 3) on selected object handshaking the exchange of signals between two computers to indicate that data transmission is proceeding successfully. hang 1. to make a computer stop in its tracks because of a software bug or hardware failure. 2. (on a modem) to disconnect from the telephone line (hang up). hanging indent, hanging tab a new paragraph indicated by letting the first word extend to the left past the normal margin into the gutter. Also called OUTDENT. Each entry in this dictionary begins with a hanging indent. Happy Mac (pre-OS X only) the icon of a smiling Macintosh that greets you when you turn on your Macintosh and everything is well. Contrast SAD MAC. hard-coded written into a computer program; not easily alterable. For instance, the location of video memory was hard-coded into the BIOS of the original IBM PC. 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 225 hard copy a printout on paper of computer output. Contrast SOFT COPY, which is a copy that is only viewable on the screen. hard disk a data storage medium using rigid aluminum disks coated with iron oxide. The read-write head travels across the disk on a thin cushion of air without ever actually touching the disk. Hard disks have much greater storage capacity than diskettes. In the early 1980s, 10 megabytes was a common size for hard disks. Today’s disks are measured in hundreds of gigabytes. See also DISK; DISKETTE; HARD DISK MANAGEMENT. On the interface between the hard disk and the computer, see ESATA; ESDI; IDE; PATA; SATA; SCSI. hard disk management a task faced by all computer users. Modern hard disks are so large that it is easy to lose track of what you have stored on them. Here are some tips: 1. Be systematic. Choose a place to put files whenever there isn’t a good reason to put them elsewhere. In Windows, the Documents folder serves this purpose. 2. Use meaningful filenames. For example, a paper about African violets should be named AfricanViolets rather than av9247 or MyPaper. Add “-old,” “-previous,” or the like when you need to keep more than one version of the same file. 3. Group files by project, not by software. For example, if you are writing a magazine article that consists of a word processing doc- ument and three pictures, create a folder for the project and put all four files in it. 4. Make backups. Your disk drive will fail one day, probably when you least expect it. 5. Learn how to search for misplaced files. In Windows, go to the Start Menu and choose Search or Find. 6. Defragment your hard disk every few weeks or months. hard drive a HARD DISK. hard drive enclosure a box in which a hard disk drive can be mounted instead of mounting it in the computer’s case. hard edge in an image, an edge that is smooth and sharp, with no blending or blurring of the boundary. See Figure 127. Contrast SOFT EDGE. FIGURE 127. Hard edge, left; Soft edge on right hard copy 226 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 226 hard error a persistent, reproducible error (defect) on a data storage device. Contrast SOFT ERROR. hard hyphen see REQUIRED HYPHEN. hard page a forced page break; a place where the word processor must begin a new page whether or not the previous page was full. In many PC word processors, the way to type a hard page is to hold down the Ctrl key while pressing Enter. hardware the physical elements of a computer system; the computer equipment as opposed to the programs or information stored in the machine. Contrast SOFTWARE. hardware interrupt a CPU interrupt triggered by a hardware event, such as pressing a key. See INTERRUPT. hardware key a device that attaches to a computer to prove that it is licensed to run a particular piece of software; a dongle. See DONGLE. Harvard architecture a type of computer design in which the program and the data are stored in separate memories. Contrast VON NEUMANN ARCHI- TECTURE. See COMPUTER ARCHITECTURE. hash function a function that converts a string of characters to a number or a shorter string. During data transmission, the value of an agreed-upon hash function can be transmitted along with the data so it can be verified if the data has been transmitted correctly. For example, see CHECKSUM. A one-way hash function is a hash function that is also a one-way function. See ENCRYPTION; ONE-WAY FUNCTION. hashing a storage mechanism where data items are stored at locations that are determined by a mathematical function of the data. For example, suppose you need to store a set of numbers in memory locations whose addresses run from 1 to 100. One example of a hashing function is to divide each number by 100 and use the remainder as the storage address. For example, the number 538 would be stored at memory location 38, and 1124 would be stored at location 24. The use of hashing makes it possible to store and retrieve the data items quickly, since it is not necessary to search through the list in order to find the item. However, there is one complication: A hashing function will sometimes assign more than one data item to the same address. For example, using the rule given, the number 638 would also be stored in location 38. To avoid that problem, a hashing system needs to be able to resolve collisions by storing the new data item in a separate place. hat 1. the character ˆ (circumflex). 2. See BLACK HAT; RED HAT; WHITE HAT. Hayes compatibility the ability of a telephone line modem to respond to the same set of autodialing commands as the Hayes Smartmodem (made 227 Hayes compatibility 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 227 by Hayes Microcomputer Products, Inc., Norcross, Georgia). Almost all modems nowadays are Hayes compatible. Modems need not be Hayes compatible in order to communicate with each other. Hayes compatibility refers only to the commands used by the computer to control the modem. They are often called the AT COMMAND SET and begin with the letters AT. For example, ATDT706-555-2345 tells the modem to dial 706-555-2345. See also MODEM; RS-232. HD DVD (high-density DVD) a high-density optical disc similar to, but not compatible with, BLU-RAY DISC, formerly marketed by Toshiba but dis- continued in 2008. HDD hard disk drive. HDMI (High-Definition Multimedia Interface) a standard interface and cable connector for carrying digitized audio and video. The connector is small and flat, like a USB connector, but is even smaller and contains 19 pins. Compare DVI (definition 1). For more information see www.hdmi.org. HDSL (High-bit-rate Digital Subscriber Line) a type of high-speed net- work connection provided through ordinary telephone lines. Unlike ordinary DSL (ADSL), HDSL is symmetric (i.e., the upload and down- load speeds are both 1.5 Mbps), but ordinary telephone service is not included. See DSL and cross-references there. HDTV high-definition television; television with a resolution of 1280 × 720 pixels or more and, normally, a widescreen format with an aspect ratio of 16:9. Although analog HDTV was attempted in the 1990s, HDTV is now broadcast digitally because digital data compression is essential to its success. Contrast SDTV. head 1. the part of a disk drive that reads and writes information magneti- cally. A double-sided disk drive or multilayered hard disk has a head for each side of each layer. (See DISK.) 2. the top of a page or printed piece (such as a newsletter). 3. short for headline. 4. tag used in HTML to indicate the beginning of the heading of a web page, which includes material such as the title. Contrast BODY. For an example, see HTML. headless term describing a computer that lacks a keyboard, screen, and a mouse. headset speakers (or rather earphones) and (usually) a microphone worn on a person’s head. heap a block of memory that belongs to a program but has not yet been HD DVD 228 7_4105_DO_CompInternetTerms_H 12/29/08 10:26 AM Page 228 [...]... 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F 50 51 52 53 54 55 56 ... right and try again Consider for example the following list: 2404 8 653 1 354 57 81 The steps of the insertion sort are the following: 1 2404 and 8 653 are in the right order, so proceed to the next pair 2 8 653 and 1 354 are in the wrong order, so pick up 1 354 : 2404 8 653 57 81 7_41 05_ DO_CompInternetTerms_I 12/29/08 10:27 AM 253 Page 253 insertion sort Shift 8 653 one space to the right: 2404 8 653 57 81 Can 1 354 ... number So shift 2404 one space to the right: 2404 8 653 57 81 Now you can put 1 354 into the empty space: 1 354 2404 8 653 57 81 3 Now examine 8 653 and 57 81 They are in the wrong order, so pick up 8 653 and shift it one space to the right, then put 57 81 into the empty space: 1 354 2404 8 653 1 354 2404 8 653 1 354 2404 57 81 8 653 Now all the elements are in order, and the process is complete Figure 139 shows a program... 140 141 142 143 144 1 45 146 147 148 149 150 151 152 153 154 155 156 157 158 159 A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 160 161 162 163 164 1 65 166 167 168 169 170 171 172 173 174 1 75 176 177 178 179 180 181 182 183 184 1 85 186 187 188 189 190 191 C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 CA CB... 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77 78 79 7A 7B 7C 7D 7E 7F = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 96 97 98 99 100 101 102 103 104 1 05 106 107... 231 232 233 234 2 35 236 237 238 239 240 241 242 243 244 2 45 246 247 248 249 250 251 252 253 254 255 HFS see HIERARCHICAL FILE SYSTEM (definition 2) hibernate to suspend the operation of a computer by copying the entire contents of memory to a disk file, so that the computer can be powered off, then turned on again to resume where it left off, without rebooting While hibernating, a computer consumes... instances of the word “aardvark” and find 250 of them, you’ve found 250 hits 7_41 05_ DO_CompInternetTerms_H 2 35 12/29/08 10:26 AM Page 2 35 hole 2 on the World Wide Web, an instance of someone elsewhere calling up the web page and viewing it The popularity of a web site is measured in hits per day hive a major section of the Windows REGISTRY that is automatically backed up on an external file Examples of hives... (compatible imitations) of it The IBM PC became the most popular standard for microcomputers, even though most of the computers were produced by other companies, and Intel microprocessors and Microsoft operating system software became the defining elements of the standard Today’s “PC” computers are distant descendents of the original IBM PC In 20 05 IBM sold its PC business to Lenovo IBM is headquartered in... web-creation software programs, or they can be defined directly by hand-coding the proper HTML image processing the use of a computer to modify pictures (usually bitmap images) Applications of image processing include computer vision, enhancement of photographs, and creation of works of art Many image processing functions are built into PAINT PROGRAMs as FILTERs (definition 7_41 05_ DO_CompInternetTerms_I... some specified differences The second type of object then “inherits” the properties of the first See OBJECT-ORIENTED PROGRAMMING INI file a file (with the extension ini) that stores initialization information for Microsoft Windows or a specific piece of software Windows INI files consist of editable text 7_41 05_ DO_CompInternetTerms_I 12/29/08 10:27 AM Page 252 252 initialize initialize 1 to store a value . = 17 31 = 49 51 = 81 71 = 113 12 = 18 32 = 50 52 = 82 72 = 114 13 = 19 33 = 51 53 = 83 73 = 1 15 14 = 20 34 = 52 54 = 84 74 = 116 15 = 21 35 = 53 55 = 85 75 = 117 16 = 22 36 = 54 56 = 86 76 =. commands used by the computer to control the modem. They are often called the AT COMMAND SET and begin with the letters AT. For example, ATDT706 -55 5-23 45 tells the modem to dial 706 -55 5-23 45. . 118 17 = 23 37 = 55 57 = 87 77 = 119 18 = 24 38 = 56 58 = 88 78 = 120 19 = 25 39 = 57 59 = 89 79 = 121 1A = 26 3A = 58 5A = 90 7A = 122 1B = 27 3B = 59 5B = 91 7B = 123 1C = 28 3C = 60 5C = 92 7C =