Barrons Publishing Dictionary of Computer and Internet Terms 10th

/home in UNIX, a directory that contains individual users’ home directories.

home directory the main directory belonging to a particular user of a UNIX system or of a file server shared by multiple users.

home page

1.the main WEB PAGE for a person or organization; the page that users are expected to read first in order to access other pages.

2.the WEB PAGE that a person sees first, immediately after starting up the BROWSER. Most browsers let you choose what web page this will be.

See also HTML; WORLD WIDE WEB.

honeypot a trap for people who tamper with computers maliciously through the Internet, just as a pot of honey traps flies.

A honeypot is generally a computer that is rigged to look more vulnerable than it really is, and to keep records of everything that happens to it. Honeypots serve several purposes: to catch individual crackers, to determine whether they can get into a network, and to observe how they carry out their attacks. See COMPUTER SECURITY; CRACKER.

hook a provision, in a computer program, for interaction with other programs that have yet to be written. For example, Adobe Photoshop and many web browsers provide hooks for plug-ins that add additional features. See PLUG-IN.

Hopper, Grace (1906–1992), mathematician and U.S. naval officer (later admiral) who worked on the first electronic computers. She developed the first compiler and contributed to the development of COBOL. For many years, she was the highest-ranking woman in the U.S. Navy.

horizontal side to side; across.

host computer a computer that provides services to others that are linked to it by a network; generally, the more remote of two or more computers that a person is using at once. For example, when a user in Florida accesses a computer in New York, the New York computer is considered the host.

hot list a list of bookmarks or favorites; a stored list of web addresses, filenames, or other data of immediate interest to the user. See BOOKMARK;

FAVORITES.

hot-pluggable able to be plugged in and unplugged while a computer is powered on and running.

hot spot

1.(sometimes hotspot) a place where wireless access to the Internet is offered, such as for customers bringing their laptops into a coffee shop.

2.a place in a hypertext document where a user can click to call up further information. Hot spots are generally highlighted words or small pictures. Some large graphics can have multiple hot spots. See ANCHOR;

HYPERLINK; IMAGE MAP.

3. the exact spot of a pointer (or any mouse cursor) that must touch an object in order to select it. The very tip of the arrow is the hot spot for the pointer.

hot-swappable able to be replaced (swapped out) while a computer is powered on and running.

hot zone the area at the end of a line of type that triggers the computer to hyphenate words. If a word extends into the hot zone, it will be hyphenated to make it fit on the line. See HYPHENATION.

hotfix a PATCH or rapidly distributed update for a piece of software. The term is used particularly with Microsoft Windows.

hourglass (in Microsoft Windows XP and earlier) the shape of the mouse pointer while the computer is too busy to accept any input from the keyboard or mouse. The pointer returns to its usual shape when the wait is over.

FIGURE 131. Hourglass

hover to leave the mouse cursor at a particular location more than momentarily, without clicking it. See ROLLOVER (definition 2).

HR keyword used in HTML to indicate a horizontal rule. For an example, see HTML.

HSB (hue, saturation, brightness) a way of describing colors by means of numbers in some computer programs. HSB descriptions are especially convenient for artists who are accustomed to mixing paint. The first number, hue, describes the color itself (red, green, blue, yellow, etc., along a continuum).

The saturation is the vividness of the color, from maximum (extremely vivid) through paler colors all the way down to gray or white. For example, going from red to pale red to gray is a change of saturation.

The brightness is the amount of light emitted from patches of the color on the screen, from maximum brightness down to black.

HSDPA (High-Speed Downlink Packet Access) a system for wireless broadband. Information available at www.3gpp.org. Contrast EVDO.

HTML (Hypertext Markup Language) a set of codes that can be inserted into text files to indicate special typefaces, inserted images, and links to other hypertext documents.

The main use of HTML is to publish information on the Internet (see WORLD WIDE WEB). Here is a simple example of an HTML document.

HTTPS a variation of HTTP that uses SSL encryption for security.

hub a device for joining multiple Ethernet cables by copying all the data packets onto all the cables. Hubs are only suitable for use with very lightly loaded networks. Compare SWITCH (definition 2); ROUTER.

hue color (red vs. green vs. orange, etc.). See HSB.

hunt and peck (slang) to type by gazing at the keyboard, hunting for the letters, and pressing them one by one with one finger, rather like a trained chicken.

Hyper-Threading the ability of some Pentium microprocessors to follow two sequences of instructions at once. The central core of the microprocessor switches back and forth between the two threads, and some of the circuitry is duplicated in order to keep track of two tasks at once.

Contrast DUAL-CORE PROCESSOR.

hyperdocument see HYPERTEXT.

hyperlink an item on a WEB PAGE which, when selected, transfers the user directly to another location in a hypertext document or to some other web page, perhaps on a different machine. Also simply called a LINK. For an example, see HTML.

hypertext (hyperdocuments) electronic documents that present information that can be read by following many different connections, instead of just sequentially like reading a book. The World Wide Web is an example of hypertext, as are Microsoft Windows help files and CD-ROM encyclopedias.

A hypertext document typically starts with a computer screen full of information (text, graphics, and/or sound). The user can then jump instantly to many other screens of information by clicking on words or pictures with a mouse or touchscreen.

Encyclopedia information is especially suitable for hypertext presentation. Each entry can be a screen of information, and each cross-refer- ence can be a button that the user can click on in order to jump to that entry. Software help files are also a good application for hypertext because the user generally needs to find a particular piece of information as quickly as possible rather than reading through the whole document.

There is a danger that the user might become lost in the middle of a hyperdocument. A good hyperdocument should include some form of navigational aid that allows the user to see an overview of the document. Also, it is helpful if the computer maintains a record of the path that has been followed, both so the user can go backward and so it is possible to retrace the same path at a future date if so desired. Often a hyperdocument follows a particular sequence automatically if the user does not want to make all of the choices individually.

A large hyperdocument (e.g., an encyclopedia) requires large amounts of storage such as provided by a CD-ROM. The World Wide Web is a

way of publishing hypertext on the Internet, using many different computers as servers for different parts of the information. See

WEB; HTML; BROWSER.

hyphenation the practice of breaking words between syllables at the end of a line so that the lines will be more nearly the same length.

Most desktop publishing software can automatically hyphenate text. The computer tries to put as many words as possible on one line. When it enters the last half inch of the line (the HOT ZONE), it calculates whether the next word will fit; if not, the word is looked up in the hyphenation dictionary, or hyphenated according to phonetic rules. The basic idea is that both parts of the word should be pronounceable. There is often more than one acceptable way to hyphenate a word, and dictionaries sometimes disagree with each other. The most basic rule is, “Make both pieces pronounceable.”

Fully justified type will always look better when hyphenated; otherwise loose lines (lines with big gaps between the words) become a problem. If you are setting type flush left, ragged right, be aware that the size of the hot zone will affect how ragged the right margin is.

Proofread carefully for unfortunate line breaks. The traditional example is the word “therapist”—don’t let the computer hyphenate it as “therapist.” Learn how to mark required hyphens so that hyphenated names and phone numbers won’t be broken across lines.

See also

Hz see HERTZ.

I

I-bar, I-beam the shape of the mouse pointer in a text editing environment.

See INSERTION POINT.

FIGURE 133. I-bar (I-beam) cursor.

I-triple-E see IEEE.

I2 see INTERNET 2.

IA-32 (Intel Architecture-32) the architecture of the Intel 80386, 80486, and Pentium microprocessors, used on the majority of the computers in existence today. Contrast IA-64.

IA-64 (Intel Architecture-64) the architecture of the 64-bit Intel microprocessors, such as the ITANIUM, that are intended to be the successor to the Pentium family (IA-32). IA-64 microprocessors can switch into IA-32 mode for compatibility with older software.

A feature of IA-64 is Explicitly Parallel Instruction Computing (EPIC), the ability to execute several instructions simultaneously when they have been grouped in parallel by the compiler. Compare HYPERTHREADING, which does not actually execute more than one instruction at once. See ITANIUM; PARALLEL PROCESSING. Contrast X64.

IANA (Internet Assigned Numbers Authority) an organization based at the University of Southern California with the responsibility to make sure all IP addresses are unique. Their web address is www.iana.org. See IP ADDRESS; TLD.

IBM (International Business Machines) manufacturer of computers and other office equipment. The company was formed in 1911 by the merger of three companies that made record-keeping equipment for businesses, one of which was the PUNCHED CARD company founded by Herman Hollerith.

IBM started manufacturing mainframe computers in the 1950s. By the late 1960s, IBM controlled about 80 percent of the computer market with models such as the IBM System/360, and the name IBM was practically synonymous with computing. Today, the company continues to make mainframe computers.

In 1981 IBM introduced the IBM Personal Computer (PC), which quickly became one of the most popular microcomputers. Users felt that with IBM behind it, the personal computer had come of age as a practi-

cal business machine, not just an experimental machine for laboratories or hobbyists. The IBM PC was designed in some haste, and very little of its design was patented; as a result, other companies (beginning with Compaq in 1983) were able to produce clones (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 2005 IBM sold its PC business to Lenovo. IBM is headquartered in Armonk, New York (web address: www.ibm.com). See also IBM PC.

IBM PC popular lines of microcomputers manufactured by IBM. There are many variations of each; this article will mention only the most historically important.

The IBM Personal Computer (PC), introduced in 1981, was the first of a family of very popular microcomputers, including not only IBM products but also “clones” (imitations) made by other companies. The original IBM PC used very little proprietary technology. Thus, it was easy for competitors to build compatible machines without violating patents. See CLONE; PC COMPATIBILITY.

IBM maintained a high level of upward compatibility within the PC and PS/2 line. This means that later-model machines would run virtually all software written for earlier models.

FIGURE 134. IBM PC (1981)

IBM’s two original machines, the PC and PC XT, are virtually identical, featuring 4.77-MHz 8088 microprocessors with an 8-bit bus. The only difference was that the XT had a 10-megabyte hard disk and had eight expansion slots instead of five. The PC AT, introduced in 1984, was the first PC to use the 80286 microprocessor, enabling programs to run much faster. The PC AT had what is now known as the ISA (Industry Standard Architecture) bus; it accepted both 8-bit (XT-style) and 16-bit plug-in cards.

The PS/2 machines were introduced in 1987 and discontinued in 1995. They were more compact than comparably configured PCs or ATs, and all but the lowest models used the Micro Channel bus, which made it possible in some situations to use more than one CPU in a single machine.

These computers use the ASCII character set (see ASCII). In addition, they define printed representations for all character codes from 0 to 255.

Figure 135 shows the printable part of the special character set. At a Windows COMMAND PROMPT, these characters are typed by holding down the Alt key and typing the appropriate number on the numeric keypad at the right side of the keyboard. For example, to type a shaded block, hold down Alt, type 178, and then release Alt.

(Note the arrangement: these are not in numerical order. 218 is the upper left corner box-drawing character; 192 is the lower left corner, and so on.)

FIGURE 135. IBM PC special characters (also used in Windows console mode)

IBM RS/6000 see WORKSTATION.

IC

1. abbreviation for “in character,” used in role playing games and the like to indicate a return to the imaginary situation after an out of character (OOC) conversation. When IC, all replies are from the user’s imagi-