L1 cache

n. A memory cache built into i486 and higher-level processors. The L1 cache, typically containing 8 KB, can be read in a single clock cycle, so it is tried first. The i486 contains one L1 cache; the Pentium contains two, one for code and one for data. Also called level 1 cache, on-chip cache. See also cache, i486DX, Pentium. Compare L2 cache.

L2 cache

n. A memory cache consisting of static RAM on a motherboard that uses an i486 or higher-level processor. The L2 cache, which typically contains 128 KB to 1 MB, is faster than the system DRAM but slower than the L1 cache built into the CPU chip. Also called level 2 cache. See also cache, dynamic RAM, i486DX, static RAM. Compare L1 cache.

label

n. An identifier. A label can be a physical item, such as a stick-on tag used to identify disks and other computer equipment, or an electronic label added to floppy disks or hard disks. It can also be a word, symbol, or other group of characters used to identify a file, a storage medium, an element defined in a computer program, or a specific item in a document such as a spreadsheet or a chart. See also identifier.

lag

n. The time difference between two events. In electronics, a lag is a delay between a change in input and a change in output. On computer displays, a lag is a fading brightness left on the phosphor coating of the screen after an image changes. See also persistence.

LAN

n. Acronym for local area network. A group of computers and other devices dispersed over a relatively limited area and connected by a communications link that enables any device to interact with any other on the network. LANs commonly include microcomputers and shared resources such as laser printers and large hard disks. The devices on a LAN are known as nodes, and the nodes are connected by cables through which messages are transmitted. See also baseband network, broadband network, bus network, collision detection, communications protocol, contention, CSMA/CD, network, ring network, star network, token bus network, token passing, token ring network. Compare wide area network.

landscape mode

n. A horizontal print orientation in which text or images are printed "sideways"--that is, the width of the image on the page is greater than the height. Compare portrait mode.

LAN Manager

n. A local area network technology developed by Microsoft Corporation and distributed by Microsoft, IBM (as IBM LAN Server), and other original equipment manufacturers. LAN Manager connects computers running the MS-DOS, OS/2, or UNIX operating system and allows users to share files and system resources and to run distributed applications using a client/server architecture. See also client/server architecture, LAN.

laptop

n. A small, portable personal computer that runs on either batteries or AC power, designed for use during travel. Laptops have flat LCD or plasma screens and small keyboards. Most can run the same software as their desktop counterparts and can accept similar peripherals, such as sound cards, internal or external modems, and floppy disks and CD-ROM drives. Some laptops are designed to be plugged into a docking station, effectively making them desktop computers. Most have connectors for plugging in external keyboards and full-sized monitors. Older laptops weighed as much as 15 pounds; current laptops can weigh as little as 5 pounds, without peripherals such as floppy disk or CD-ROM drives. While notebook is the current term for ultralight portable computers, these machines are also commonly referred to as laptops. See also portable computer. Compare subnotebook computer.

large-scale integration

n. A term describing the concentration of between 100 and 5,000 circuit elements on a single chip. See also integrated circuit. Compare medium-scale integration, small-scale integration, super-large-scale integration, ultra-large-scale integration, very-large-scale integration. Acronym: LSI.

laser

or LASER n. Acronym for light amplification by stimulated emission of radiation. A device that uses certain quantum effects to produce coherent light, which travels with greater efficiency than noncoherent light because the beam diverges only slightly as it travels. Lasers are used in computer technology to transmit data through fiber-optic cables, to read and write data on CD-ROMs, and to place an image on a photosensitive drum in laser printers.

laser printer

n. An electrophotographic printer that is based on the technology used by photocopiers. A focused laser beam and a rotating mirror are used to draw an image of the desired page on a photosensitive drum. This image is converted on the drum into an electrostatic charge, which attracts and holds toner. A piece of electrostatically charged paper is rolled against the drum, which pulls the toner away from the drum and onto the paper. Heat is then applied to fuse the toner to the paper. Finally, the electrical charge is removed from the drum, and the excess toner is collected. By omitting the final step and repeating only the toner-application and paper-handling steps, the printer can make multiple copies. The only serious drawback of a laser printer is that it offers less paper-handling flexibility than do dot-matrix printers. Both multipart forms and wide-carriage printing, for example, are better handled by line printers, dot-matrix printers, or daisy-wheel printers. See also electrophotographic printers, nonimpact printer, page printer. Compare daisy-wheel printer, dot-matrix printer, ion-deposition printer, LCD printer, LED printer.

latency

n. The time required for a signal to travel from one point on a network to another. See also ping¹ (definition 1).

launch

vb. To activate an application program (especially on the Macintosh) from the operating system's user interface.

layer

n. 1. The protocol or protocols operating at a particular level within a protocol suite, such as IP within the TCP/IP suite. Each layer is responsible for providing specific services or functions for computers exchanging information over a communications network, such as the layers outlined in the ISO/OSI model shown in the table below, and information is passed from one layer to the next. Although different suites have varying numbers of levels, generally the highest layer deals with software interactions at the application level, and the lowest governs hardware-level connections between different machines. See also ISO/OSI model, protocol stack, TCP/IP. 2. In communications and distributed processing, a set of rules and standards that handle a particular class of events. k:\compdict\database\687.doc

layered interface

n. In programming, one or more levels of routines lying between an application and the computing hardware and separating activities according to the type of task the activities are designed to carry out. Ultimately, such an interface makes it easier to adapt a program to different types of equipment.

layering

n. In computer graphics, the grouping of logically related elements in a drawing. Layering enables a program user to view, and work on independently, portions of a graphic instead of the entire drawing.

layout

n. 1. The overall plan or design of a document system. See also page layout. 2. In programming, the order and sequence of input and output. 3. In computer design, the arrangement of circuits and other components of the system.

lcd

n. In some FTP clients, the command that changes the current directory on the local system. See also FTP client.

LCD printer

n. Short for liquid crystal display printer. An electrophotographic printer similar to a laser printer and often incorrectly labeled as one. LCD printers use a bright light source, typically a halogen lamp. Also called liquid crystal shutter printer. See also electrophotographic printers, nonimpact printer, page printer. Compare ion-deposition printer, laser printer, LED printer.

LCD projector

n. Short for liquid crystal display projector. A device that casts an image of a computer's video output from a liquid crystal display onto a screen. See also liquid crystal display.

LDAP

n. See Lightweight Directory Access Protocol.

leaf

n. Any node (location) in a tree structure that is at the farthest distance from the root (primary node), no matter which path is followed. Thus, in any tree, a leaf is a node at the end of a branch--one that has no descendants. See also root, subtree, tree.

least significant bit

n. In a sequence of one or more bytes, the low-order (usually rightmost) bit of a binary number. See also low-order. Compare most significant bit. Acronym: LSB.

least significant character

n. The low-order, or rightmost, character in a string. See also low-order. Compare most significant character. Acronym: LSC.

least significant digit

n. The low-order, or rightmost, digit in the normal representation of a number. See also low-order. Compare most significant digit. Acronym: LSD.

LED printer

n. Short for light-emitting diode printer. An electrophotographic printer similar to LCD and laser printers. The significant difference between LED and laser or LCD printers is in the light source; LED printers use an array of light-emitting diodes. See also electrophotographic printers, light-emitting diode, nonimpact printer, page printer. Compare ion-deposition printer, laser printer, LCD printer.

left justification

n. In typesetting, word processing, and desktop publishing, the process of aligning text evenly along the left margin of a column or page. The right edge of the text is ragged. See also justify (definition 1), rag. Compare full justification, right justification.

left-justify

vb. To justify, as text, along the left. See also justify (definition 1), rag. Compare right-justify.

legacy

adj. Of or pertaining to documents or data that existed prior to a certain time. The designation refers particularly to a change in process or technique that requires translating old data files to a new system.

letterbomb

n. An e-mail message that is intended to impair the recipient's computer use. Some sequences of control characters can lock up a terminal, files attached to the message may contain viruses or Trojan horses, and a sufficiently large message can overflow a mailbox or crash a system. See also control character, e-mail¹ (definition 1), mailbox, Trojan horse, virus.

letter quality

adj. Pertaining to or being a level of print quality on dot-matrix printers that is better than draft quality. As the name implies, letter quality is supposed to be crisp and dark enough for use in business letters. See also print quality. Compare draft quality, near-letter-quality.

lexicon

n. 1. The words of a language and their definitions. 2. In programming, the identifiers, keywords, constants, and other elements of a language that make up its "vocabulary." The ways in which these vocabulary elements can be put together is the syntax of the language. Compare syntax.

LHARC

n. A freeware file-compression utility program developed by Haruyasu Yoshizaki and introduced in 1988. With LHARC, the contents of one or more files can be compressed into a singular, smaller file, with the extension .lha. A copy of the program is required to uncompress these files. LHARC can also embed a small program with the compressed information and save everything in a single file, called a self-extracting archive, with an .exe extension. As a result, the recipient of the compressed file does not need a separate utility program to uncompress the file. See also freeware, PKZIP, utility program.

library

n. 1. In programming, a collection of routines stored in a file. Each set of instructions in a library has a name, and each performs a different task. 2. A collection of software or data files.

licensing key

n. A short character string that serves as a password during the installation of licensed commercial software. The use of licensing keys is a security device aimed at reducing illegal duplication of licensed software.

light-emitting diode

n. A semiconductor device that converts electrical energy into light, used, for example, for the activity lights on computer disk drives. Light-emitting diodes work on the principle of electroluminescence and are highly efficient, producing little heat for the amount of light output. Acronym: LED.

Linotronic

n. Any in the series of high-quality typesetting devices known as Linotronic laser imagesetters, which can print at resolutions such as 1,270 and 2,540 dots per inch (dpi). These devices are commonly attached to PostScript raster image processors (RIPs) so that desktop publishing applications can typeset directly from a microcomputer. See also imagesetter, PostScript, raster image processor.

Linux

n. A version of the UNIX System V Release 3.0 kernel developed for PCs with 80386 and higher-level microprocessors. Developed by Linus Torvalds of Sweden (for whom it is named) along with numerous collaborators worldwide, Linux is distributed free with source code through BBSs and the Internet, although some companies distribute it as part of a commercial package with Linux-compatible utilities. The Linux kernel works with the GNU utilities developed by the Free Software Foundation, which did not produce a kernel. See also free software, GNU, kernel, UNIX.

LIPS

n. 1. Acronym for Language Independent Program Subtitling. A system developed by the GIST group (C-DAC, India) and used by Indian Television for nationwide broadcast of programs with multilingual subtitles in teletext mode. This system was judged the best design in the VLSI design contest in the VLSI '93 International Conference. Three versions of this application-specific integrated circuit (ASIC) with different features were implemented in Xilinx 3K and 4K series FPLAs. See also field-programmable logic array, gate array, very-large-scale integration. 2. Acronym for linear inferences per second. A measure of speed for some types of artificial-intelligence machines and expert systems. See also artificial intelligence, expert system. See Lightweight Internet Person Schema.

liquid crystal display

n. A type of display that uses a liquid compound having a polar molecular structure, sandwiched between two transparent electrodes. When an electric field is applied, the molecules align with the field, forming a crystalline arrangement that polarizes the light passing through it. A polarized filter laminated over the electrodes blocks polarized light. In this way, a grid of electrodes can selectively "turn on" a cell, or a pixel, containing the liquid crystal material, turning it dark. In some types of liquid crystal displays, an electroluminescent panel is placed behind the screen to illuminate it. Other types of liquid crystal displays are capable of reproducing color. Acronym: LCD.

LISP

n. Acronym for List Processing. A list-oriented programming language developed in 1959-60 by John McCarthy and used primarily to manipulate lists of data. LISP is heavily used in research and academic circles and is considered the standard language for artificial-intelligence research. See also artificial intelligence. Compare Prolog.

list

n. A multi-element data structure that has a linear (first, second, third, . . .) organization but that allows elements to be added or removed in any order. Queues, deques, and stacks are simply lists with restrictions on adding and removing elements. See also deque, element (definition 1), linked list, queue, stack.

list box

n. A control in Microsoft Windows that enables the user to choose one option from a list of possibilities. The list box appears as a box, displaying the currently selected option, next to a button marked with a down-arrow. When the user clicks on the button, the list appears. The list has a scroll bar if there are more options than the list has room to show.

LISTSERV

n. One of the most popular commercial mailing list managers, marketed by L-SOFT International in versions for BITNET, UNIX, and Windows. See also mailing list, mailing list manager.

Live3D

n. A Netscape proprietary Virtual Reality Modeling Language (VRML) plug-in for Web browsers that allows users to view and interact with a virtual-reality world. See also VRML.

load¹

n. 1. The total computing burden a system carries at one time. 2. In electronics, the amount of current drawn by a device. 3. In communications, the amount of traffic on a line.

load²

vb. To place information from storage into memory for processing, if it is data, or for execution, if it is program code.

loader

n. A utility that loads the executable code of a program into memory for execution. On most microcomputers, the loader is an invisible part of the operating system and is automatically invoked when a program is run. See also loader routine, load module.

LocalTalk

n. An inexpensive cabling scheme used by AppleTalk networks to connect Apple Macintosh computers, printers, and other peripheral devices. See also AppleTalk.

location

n. See address¹ (definition 1).

lock

n. 1. A software security feature that requires a key or dongle in order for the application to run correctly. See also dongle. 2. A mechanical device on some removable storage medium (for example, the write-protect notch on a floppy disk) that prevents the contents from being overwritten. See also write-protect notch.

log

n. A record of transactions or activities that take place on a computer system. See logarithm.

logic

n. In programming, the assertions, assumptions, and operations that define what a given program does. Defining the logic of a program is often the first step in developing the program's source code. See also formal logic.

logical

adj. 1. Based on true and false alternatives as opposed to arithmetic calculation of numeric values. For example, a logical expression is one that, when evaluated, has a single outcome, either true or false. See also Boolean algebra. Compare fuzzy logic. 2. Of or pertaining to a conceptual piece of equipment or frame of reference, regardless of how it may be realized physically. Compare physical.

logical device

n. A device named by the logic of a software system, regardless of its physical relationship to the system. For example, a single floppy disk drive can simultaneously be, to the MS-DOS operating system, both logical drive A and drive B.

logical drive

n. See logical device.

logical link control

n. See IEEE 802 standards.

logoff

n. The process of terminating a session with a computer accessed through a communications line. Also called logout.

log off

vb. To terminate a session with a computer accessed through a communications line--usually a computer that is both distant and open to many users. Also called log out. Compare log on.

logon

n. The process of identifying oneself to a computer after connecting to it over a communications line. Also called login.

log on

vb. To identify oneself to a computer after connecting to it over a communications line. During the procedure, the computer usually requests the user's name and password. Also called log in. Compare log off.

LOL

Acronym for laughing out loud. An interjection used in e-mail, online forums, and chat services to express appreciation of a joke or other humorous occurrence.

long filenames

n. A feature of most current PC operating systems, notably Windows 95, Windows NT, and OS/2, that allows a user to assign a plain-text name to a file, rather than limiting possible names to just a few characters. Names can be over 200 characters long, include upper and lowercase letters, and have spaces between characters. Compare 8.3.

loop¹

n. 1. A set of statements in a program executed repeatedly, either a fixed number of times or until some condition is true or false. See also DO loop, FOR loop, infinite loop, iterative statement. 2. A pair of wires that runs between a telephone central office and customer premises.

loop²

vb. To execute a group of statements repeatedly.

lowercase

adj. In reference to letters, not capital--for example, a, b, c. Compare uppercase.

low-level language

n. A language that is machine dependent or that offers few control instructions and data types. Each statement in a program written in a low-level language usually corresponds to one machine instruction. See also assembly language. Compare high-level language.

LPMUD

n. A type of multi-user dungeon (MUD), typically combat related, that contains its own object-oriented programming language for the creation of new areas and objects in the virtual world. See also MUD.

LPT

n. Logical device name for a line printer, a name reserved by the MS-DOS operating system for up to three parallel printer ports designated LPT1, LPT2, and LPT3. The first port, LPT1, is usually the same as the primary MS-DOS hard-copy output device PRN (the logical device name for the printer). The letters LPT were originally used to stand for line print terminal.

ls

n. A UNIX command that instructs the server to return a list of files and subdirectories in the current directory or the directory specified in the command. Because many FTP sites are built on UNIX systems, this command can also be used on those sites. See also FTP site, UNIX.

LS-120

n. A floppy disk drive that is capable of storing 120 MB of data on a single 3.5-inch floppy disk. LS-120 drives are also compatible with other floppy disk formats.

LU

n. Acronym for logical unit. In an IBM SNA network, a point denoting the beginning or end of a communications session. See also SNA.

luggable computer

n. The first portable computers, produced in the early to mid-1980s. These early units, all of which had built-in CRT-based displays, weighed over 20 pounds and were the size of a medium suitcase--hence their name. See also portable computer.

lurk

vb. To receive and read articles or messages in a newsgroup or other online conference without contributing anything to the ongoing exchange.

lurker

n. A person who lurks in a newsgroup or other online conference. See also lurk. Compare netizen.

Lynx

n. A text-only Web browser program for UNIX platforms.

LZW compression