MAC

n. Acronym for media access control. See IEEE 802 standards.

Mac-

prefix A prefix used to indicate a software product's applicability for the Apple Macintosh computer, as in MacDraw.

Mac clone

n. A computer licensed and built to run the Macintosh operating system. Power Computing was named as the first licensee of the Macintosh OS in December 1994. See also Macintosh.

Mach

n. A variant of the UNIX operating system developed at Carnegie-Mellon University. Mach was designed to support advanced features such as multitasking and multiprocessing. See also UNIX.

machine address

n. See absolute address.

Macintosh

n. A popular series of personal computers introduced by the Apple Computer Corporation in January 1984. The Macintosh was one of the earliest personal computers to incorporate a graphical user interface and the first to use 3.5-inch floppy disks. It was also the first to use the 32-bit Motorola 68000 microprocessor. Despite its user-friendly features, the Macintosh has lost market share during the 1990s, losing ground to PC-compatible computers, but still enjoys widespread use in desktop publishing and graphics-related applications. Also called Mac. See also graphical user interface, PC-compatible.

Macintosh Application Environment

n. A system shell for open RISC-based systems that provides a Macintosh interface within an X Window System window. The Macintosh Application Environment is both Mac- and UNIX-compatible and will support all off-the-shelf products for the Macintosh. See also RISC, X Window System. Acronym: MAE.

Macintosh File System

n. The early, flat file system used on the Macintosh before the Hierarchical File System was introduced. See also flat file system. Compare Hierarchical File System. Acronym: MFS.

Mac OS

n. Short for Macintosh operating system. The name given to the Macintosh operating system, beginning with version 7.5 in September 1994, when Apple started licensing the software to other computer manufacturers. See also Macintosh.

macro

n. 1. In applications, a set of keystrokes and instructions recorded and saved under a short key code or macro name. When the key code is typed or the macro name is used, the program carries out the instructions of the macro. Users can create a macro to save time by replacing an often-used, sometimes lengthy, series of strokes with a shorter version. 2. In programming languages, such as C or assembly language, a name that defines a set of instructions that are substituted for the macro name wherever the name appears in a program (a process called macro expansion) when the program is compiled or assembled. Macros are similar to functions in that they can take arguments and in that they are calls to lengthier sets of instructions. Unlike functions, macros are replaced by the actual instructions they represent when the program is prepared for execution; function instructions are copied into a program only once. Compare function (definition 2).

macro instruction

n. An instruction used to manage macro definitions. See also macro language.

macro virus

n. A virus that is written in a macro language associated with an application. The macro virus is carried by a document file used with that application and executes when the document is opened.

MacTCP

n. A Macintosh extension that allows Macintosh computers to use TCP/IP. See also TCP/IP.

magnetic disk

n. A computer disk enclosed in a protective case (hard disk) or jacket (floppy disk) and coated with a magnetic material that enables data to be stored in the form of changes in magnetic polarity (with one polarity representing a binary 1 and the other a 0) on many small sections (magnetic domains) of the disk surface. Magnetic disks should be protected from exposure to sources of magnetism, which can damage or destroy the information they hold. See also disk, floppy disk, hard disk. Compare compact disc, magneto-optic disc.

magneto-optical recording

n. A type of recording technology used with optical discs in which a laser beam heats a small portion of the magnetic material covering the disc. The heating enables a weak magnetic field to change the orientation of the portion, thus recording onto the disc. This technique can also be used to erase the disc, making the disc rewritable.

magneto-optic disc

n. An erasable or semi-erasable storage disc, similar to a CD-ROM disc and of very high capacity, in which a laser beam is used to heat the recording surface to a point at which tiny regions on the surface can be magnetically aligned to store bits of data. See also CD-ROM, magneto-optical recording.

mailbomb¹

n. An excessively large amount of e-mail data (a very large number of messages or one very large message) sent to a user's e-mail address in an attempt to make the user's mailer program crash or to prevent the user from receiving further legitimate messages. See also e-mail (definition 1). Compare letterbomb.

mailbomb²

vb. To send a mailbomb to a user. One person might mailbomb a user with a single enormous message; a large number of users might mailbomb an unpopular person by simultaneously sending messages of normal size.

mailer-daemon

n. A program used to transport e-mail between hosts on a network. See also daemon.

mail merge

n. A mass-mail facility that takes names, addresses, and sometimes pertinent facts about recipients and merges the information into a form letter or another such basic document.

mailto

n. The Internet protocol used to send electronic mail.

mainframe computer

n. A high-level computer designed for the most intensive computational tasks. Mainframe computers are often shared by multiple users connected to the computer by terminals. See also computer, supercomputer.

Majordomo

n. The name of a popular software program that manages and supports Internet mailing lists. See also mailing list, mailing list manager.

major geographic domain

n. A two-character sequence in an Internet domain name address that indicates the country in which a host is located. The major geographic domain is the last part of the of the domain name address, following the subdomain and domain codes; for example, uiuc.edu.us indicates a host at the University of Illinois in the United States, whereas cam.ac.uk indicates a host at the University of Cambridge in the United Kingdom. The code .us, which indicates a domain in the United States, is usually omitted. Also called country code. See also DNS (definition 1), domain name address.

male connector

n. A type of connector that has pins for insertion into receptacles. Male connector part numbers often include an M (male) or P (plug). For example, a male DB-25 connector might be labeled DB-25M or DB-25P. Compare female connector.

MAN

n. Acronym for metropolitan area network. A high-speed network that can carry voice, data, and images at up to 200 Mbps or faster over distances of up to 75 km. Based on the network architecture, the transmission speed can be higher for shorter distances. A MAN, which can include one or more LANs as well as telecommunications equipment such as microwave and satellite relay stations, is smaller than a wide area network but generally operates at a higher speed. Compare LAN, wide area network.

management information service

n. A department within an organization that functions as a clearinghouse for information. Acronym: MIS.

management information system

n. A computer-based system for processing and organizing information so as to provide various levels of management within an organization with accurate and timely information needed for supervising activities, tracking progress, making decisions, and isolating and solving problems. Acronym: MIS.

map¹

n. Any representation of the structure of an object. For example, a memory map describes the layout of objects in an area of memory, and a symbol map lists the associations between symbol names and memory addresses in a program. See also image map.

map²

vb. To translate one value into another. For example, in computer graphics one might map a three-dimensional image onto a sphere. In reference to virtual memory systems, a computer might translate (map) a virtual address into a physical address. See also virtual memory.

MAPI

n. Acronym for Messaging Application Programming Interface. The Microsoft interface specification that allows different messaging and workgroup applications (including e-mail, voice mail, and fax) to work through a single client, such as the Exchange client included with Windows 95 and Windows NT. See also application programming interface.

mapped drives

n. 1. In the Windows environment, network drives that have been assigned local drive letters and are locally accessible. 2. Under UNIX, disk drives that have been defined to the system and can be made active.

markup language

n. A set of codes in a text file that instruct a computer how to format it on a printer or video display or how to index and link its contents. Examples of markup languages are Hypertext Markup Language (HTML), which is used in Web pages, and Standard Generalized Markup Language (SGML), which is used for typesetting and desktop publishing purposes and in electronic documents. Markup languages of this sort are designed to enable documents and other files to be platform-independent and highly portable between applications. See also HTML, SGML.

marquee

n. A nonstandard HTML extension that causes scrolling text to appear as part of a Web page. Currently, marquees are viewable only with Internet Explorer. See also HTML, Internet Explorer, Web page.

mask

n. A binary value used to selectively screen out or let through certain bits in a data value. Masking is performed by using a logical operator (AND, OR, XOR, NOT) to combine the mask and the data value. For example, the mask 00111111, when used with the AND operator, removes (masks off) the two uppermost bits in a data value but does not affect the rest of the value. See also logical operator, mask bit.

mass storage

n. A generic term for disk, tape, or optical disc storage of computer data, so called for the large masses of data that can be stored in comparison with computer memory capacity. Compare memory.

maximize

vb. In a graphical user interface, to cause a window to expand to fill all of the space available within a larger window or on the screen. See also enlarge, graphical user interface, Maximize button, window. Compare minimize, reduce.

Maximize button

n. In Windows 3.x, Windows 95, and Windows NT, a button in the upper right-hand corner of a window that, when clicked, maximizes a window to fill all of the space available within a larger window or on the screen. See also graphical user interface, window. Compare Minimize button.

MB

n. See megabyte.

Mb

n. See megabit.

Mbps

n. Acronym for megabits per second. One million bits per second.

MCI

n. 1. Acronym for Media Control Interface. Part of the Windows application programming interface that enables a program to control multimedia devices. 2. A major long-distance telephone service carrier, originally Microwave Communications, Inc.

MDI

n. Acronym for multiple-document interface. A user interface in an application that allows the user to have more than one document open at the same time. See also user interface.

media

n. The physical material, such as paper, disk, and tape, used for storing computer-based information. Media is plural; medium is singular.

media access control

n. See IEEE 802 standards.

media filter

n. 1. A device used with local area networks (LANs) as an adapter between two different types of media. For example, an RJ-45 connector might be used between coaxial cable and unshielded twisted pair (UTP) cables. Media filters are similar in function to transceivers. As with many components to LANs, manufacturers often choose different names for similar products, so a LAN expert is needed to decide what media filters are required for a particular LAN. See also coaxial cable, connector (definition 1), LAN, transceiver, UTP. 2. A device added to data networks to filter out electronic noise from the environment. For example, a media filter might be added to an Ethernet network based on coaxial cabling to prevent data loss from interference by nearby electronic equipment. See also coaxial cable, Ethernet (definition 1).

medium²

n. A substance in which signals can be transmitted, such as a wire or fiber-optic cable. See media.

megabit

n. Abbreviated Mb or Mbit. Usually 1,048,576 bits (2²⁰); sometimes interpreted as 1 million bits.

megabyte

n. Abbreviated MB. Usually 1,048,576 bytes (2²⁰); sometimes interpreted as 1 million bytes.

megahertz

n. Abbreviated MHz. A measure of frequency equivalent to 1 million cycles per second.

memory

n. A device where information can be stored and retrieved. In the most general sense, memory can refer to external storage such as disk drives or tape drives; in common usage, it refers only to the fast semiconductor storage (RAM) directly connected to the processor. See also core, EEPROM, EPROM, flash memory, PROM, RAM, ROM. Compare bubble memory, mass storage.

memory chip

n. An integrated circuit devoted to memory storage. The memory storage can be volatile and hold data temporarily, such as RAM, or nonvolatile and hold data permanently, such as ROM, EPROM, EEPROM, or PROM. See also EEPROM, EPROM, integrated circuit, nonvolatile memory, PROM, RAM, volatile memory.

memory management

n. 1. In operating systems for personal computers, procedures for optimizing the use of RAM (random access memory). These procedures include selectively storing data, monitoring it carefully, and freeing memory when the data is no longer needed. Most current operating systems optimize RAM usage on their own; some older operating systems, such as early versions of MS-DOS, required the use of third-party utilities to optimize RAM usage and necessitated that the user be more knowledgeable about how the operating system and applications used memory. See also memory management unit, RAM. 2. In programming, the process of ensuring that a program releases each chunk of memory when it is no longer needed. In some languages, such as C and C++, the programmer must keep track of memory usage by the program. Java, a newer language, automatically frees any chunk of memory that is not in use. See also C++, C, garbage collection, Java.

memory management program

n. 1. A program used to store data and programs in system memory, monitor their use, and reassign the freed space following their execution. 2. A program that uses hard disk space as an extension of the random access memory (RAM).

menu

n. A list of options from which a user can make a selection in order to perform a desired action, such as choosing a command or applying a particular format to part of a document. Many application programs, especially those that offer a graphical interface, use menus as a means of providing the user with an easily learned, easy-to-use alternative to memorizing program commands and their appropriate usage.

menu bar

n. A rectangular bar displayed in an application program's on-screen window, often at the top, from which menus can be selected by the user. Names of available menus are displayed in the menu bar; choosing one with the keyboard or with a mouse causes the list of options in that menu to be displayed.

menu-driven

adj. Using menus to present choices of commands and available options. Menu-driven programs are usually considered friendlier and easier to learn than programs with a command-line interface. Compare command-line interface.

menu item

n. A choice on a menu, selectable by either the keyboard or a mouse. In some instances, a menu item that is not available (that is, not appropriate) for a given situation is "grayed" (dimmed in comparison to the valid menu choices).

merge

vb. To combine two or more items, such as lists, in an ordered way and without changing the basic structure of either. Compare concatenate.

message

n. 1. In communications, a unit of information transmitted electronically from one device to another. A message can contain one or more blocks of text as well as beginning and ending characters, control characters, a software-generated header (destination address, type of message, and other such information), and error-checking or synchronizing information. A message can be routed directly from sender to receiver through a physical link, or it can be passed, either whole or in parts, through a switching system that routes it from one intermediate station to another. See also asynchronous transmission, block (definition 4), control character (definition 1), frame (definition 1), frame (definition 2), header (definition 2), message switching, network, packet (definition 1), packet switching, synchronous transmission. 2. In software, a piece of information passed from the application or operating system to the user to suggest an action, indicate a condition, or inform that an event has occurred. 3. In message-based operating environments, such as Microsoft Windows, a unit of information passed among running programs, certain devices in the system, and the operating environment itself.

message of the day

n. A daily bulletin for users of a network, multiuser computer, or other shared system. In most cases, users are shown the message of the day when they log into the system. Acronym: MOTD.

message queue

n. An ordered list of messages awaiting transmission, from which they are taken up on a first in, first out (FIFO) basis.

messaging

n. The use of computers and data communication equipment to convey messages from one person to another, as by e-mail, voice mail, or fax.

micro-

prefix 1. In nonexact measurements, small or compact, as in microprocessor or microcomputer. 2. Metric prefix meaning 10^-6 (one millionth).

Micro Channel Architecture

n. The design of the bus in IBM PS/2 computers (except Models 25 and 30). The Micro Channel is electrically and physically incompatible with the IBM PC/AT bus. Unlike the PC/AT bus, the Micro Channel functions as either a 16-bit or a 32-bit bus. The Micro Channel also can be driven independently by multiple bus master processors.

microcomputer

n. A computer built around a single-chip microprocessor. Less powerful than minicomputers and mainframe computers, microcomputers have nevertheless evolved into very powerful machines capable of complex tasks. Technology has progressed so quickly that state-of-the-art microcomputers are as powerful as mainframes of only a few years ago, at a fraction of the cost. See also computer.

microphone

n. 1. A device that converts sound waves into analog electrical signals. Additional hardware can convert the microphone's output into digital data that a computer can process; for example, to record multimedia documents or analyze the sound signal. 2. A communications program that runs on the Apple Macintosh.

microprocessor

n. A central processing unit (CPU) on a single chip. A modern microprocessor can have over 1 million transistors in an integrated-circuit package that is roughly 1 inch square. Microprocessors are at the heart of all personal computers. When memory and power are added to a microprocessor, all the pieces, excluding peripherals, required for a computer are present. The most popular lines of microprocessors today are the 680x0 family from Motorola, which powers the Apple Macintosh line, and the 80x86 family from Intel, which is at the core of all IBM PC-compatible and PS/2 computers. See also 6502, 65816, 6800, 68000, 68020, 68030, 68040, 80286, 80386DX, 80386SX, 8080, 8086, 8088, 88000, DECchip 21064, i486DX, i486DX2, i486SL, i486SX, Pentium, Pentium Pro, PowerPC, SPARC, Z80.

microwave relay

n. A communications link that uses point-to-point radio transmissions at frequencies higher than approximately 1 gigahertz (1,000 megahertz).

middleware

n. 1. Software that sits between two or more types of software and translates information between them. Middleware can cover a broad spectrum of software and generally sits between an application and an operating system, a network operating system, or a database management system. Examples of middleware include CORBA and other object broker programs and network control programs. See also CORBA. 2. Software that provides a common application programming interface (API). Applications written using that API will run in the same computer systems as the middleware. An example of this type of middleware is ODBC, which has a common API for many types of databases. See also application programming interface, ODBC. 3. Software development tools that enable users to create simple programs by selecting existing services and linking them with a scripting language. See also scripting language.

MIDI

n. Acronym for Musical Instrument Digital Interface. A serial interface standard that allows for the connection of music synthesizers, musical instruments, and computers. The MIDI standard is based partly on hardware and partly on a description of the way in which music and sound are encoded and communicated between MIDI devices. The information transmitted between MIDI devices is in a form called a MIDI message, which encodes aspects of sound such as pitch and volume as 8-bit bytes of digital information. MIDI devices can be used for creating, recording, and playing back music. Using MIDI, computers, synthesizers, and sequencers can communicate with each other, either keeping time or actually controlling the music created by other connected equipment. See also synthesizer.

migration

n. The process of making existing applications and data work on a different computer or operating system.

MILNET

n. Short for Military Network. A wide area network that represents the military side of the original ARPANET. MILNET carries nonclassified U.S. military traffic. See also ARPANET. Compare NSFnet.

MIME

n. Acronym for Multipurpose Internet Mail Extensions. A standard that extends the Simple Mail Transfer Protocol (SMTP) to permit data, such as video, sound, and binary files, to be transmitted by Internet e-mail without having to be translated into ASCII format first. This is accomplished by the use of MIME types, which describe the contents of a document. A MIME-compliant application sending a file, such as some e-mail programs, assigns a MIME type to the file. The receiving application, which must also be MIME-compliant, refers to a standardized list of documents that are organized into MIME types and subtypes to interpret the content of the file. For instance, one MIME type is text, and it has a number of subtypes, including plain and html. A MIME type of text/html refers to a file that contains text written in HTML. MIME is part of HTTP, and both Web browsers and HTTP servers use MIME to interpret e-mail files they send and receive. See also HTTP, HTTP server, Simple Mail Transfer Protocol, Web browser. Compare BinHex¹ (definition 1).

minimize

vb. In a graphical user interface, to hide a window without shutting down the program responsible for the window. Usually an icon, button, or name for the window is placed on the desktop; when the user clicks on the button, icon, or name, the window is restored to its previous size. See also graphical user interface, Minimize button, taskbar, window. Compare maximize.

Minimize button

n. In Windows 3.x, Windows 95, and Windows NT, a button in the upper right-hand corner of a window that when clicked on hides the window. In Windows 3.x and Windows NT 3.5 and lower, an icon appears on the desktop that represents the window; in Windows 95 and Windows NT 4.0, the name of the window appears on the taskbar at the bottom of the desktop screen. When the icon or the name is clicked on, the window is restored to its previous size. See also graphical user interface, taskbar, window.

miniport drivers

n. Drivers containing device-specific information that communicate with non-device-specific port drivers, which in turn communicate with the system. See also driver.

minitower

n. A vertical floor-standing computer cabinet that is about half the height (13 inches) of a tower case (24 inches). See also tower.

mirror image

n. An image that is an exact duplicate of the original with the exception that one dimension is reversed. For example, "<" and ">" are mirror images.

mirroring

n. In computer graphics, the ability to display a mirror image of a graphic--a duplicate rotated or reflected relative to some reference such as an axis of symmetry.

mirror site

n. A file server that contains a duplicate set of files to the set on a popular server. Mirror sites exist to spread the distribution burden over more than one server or to eliminate the need to use high-demand international circuits.

MIS

n. See management information service, management information system.

misc. newsgroups

n. Usenet newsgroups that are part of the misc. hierarchy and have the prefix misc. These newsgroups cover topics that do not fit into the other standard Usenet hierarchies (comp., news., rec., sci., soc., talk.). See also newsgroup, traditional newsgroup hierarchy, Usenet.

mixed cell reference

n. In spreadsheets, a cell reference (the address of a cell needed to solve a formula) in which either the row or the column is relative (automatically changed when the formula is copied or moved to another cell) while the other is absolute (not changed when the formula is copied or moved). See also cell.

MMX

n. Short for Multimedia Extensions. An enhancement to the architecture of Intel Pentium processors that improves the performance of multimedia and communications applications.

mnemonic

n. A word, rhyme, or other memory aid used to associate a complex or lengthy set of information with something that is simple and easy to remember. Mnemonics are widely used in computing. Programming languages other than machine language, for example, are known as symbolic languages because they use short mnemonics, such as ADD (for addition) and def (for define) to represent instructions and operations. Similarly, operating systems and applications based on typed commands use mnemonics to represent instructions to the program. MS-DOS, for example, uses dir (for directory) to request a list of files.

mobile computing

n. The process of using a computer while traveling. Mobile computing usually requires a battery-powered portable computer rather than a desktop system.

mode

n. The operational state of a computer or a program. For example, edit mode is the state in which a program accepts changes to a file. See also address mode, compatibility mode, safe mode, video mode, virtual real mode.

model

n. A mathematical or graphical representation of a real-world situation or object--for example, a mathematical model of the distribution of matter in the universe, a spreadsheet (numeric) model of business operations, or a graphical model of a molecule. Models can generally be changed or manipulated so that their creators can see how the real version might be affected by modifications or varying conditions. See also modeling, simulation.

modem

n. Short for modulator/demodulator. A communications device that enables a computer to transmit information over a standard telephone line. Because a computer is digital (works with discrete electrical signals representing binary 1 and binary 0) and a telephone line is analog (carries a signal that can have any of a large number of variations), modems are needed to convert digital to analog and vice versa. When transmitting, modems impose (modulate) a computer's digital signals onto a continuous carrier frequency on the telephone line. When receiving, modems sift out (demodulate) the information from the carrier and transfer it in digital form to the computer. Sophisticated modems are also capable of such functions as automatic dialing, answering, and redialing in addition to transmitting and receiving. Without appropriate communications software, however, modems cannot perform any useful work. See also baud rate.

modem bank

n. A collection of modems connected to a server maintained by an ISP or the operator of a BBS or remote-access LAN. Most modem banks are configured to allow a remote user to dial a single phone number that routes calls to an available phone number on the bank. See also BBS (definition 1), ISP, LAN.

modem eliminator

n. A device that enables two computers to communicate without modems. See also null modem.

modem port

n. A serial port used for connecting an external modem to a personal computer. See also modem, serial port.

moderated discussion

n. Communication taking place on a mailing list, newsgroup, or other online forum that is edited by a moderator. When one submits a message to a moderated discussion, the moderator decides if the message is relevant to the discussion topic. If so, it is forwarded to the discussion group. The content of a moderated discussion is often perceived as more valuable than that of an unmoderated one because the information has been read and approved by a "gatekeeper," who has (presumably) filtered out irrelevant submissions. Some moderators also filter submissions for obscene or pornographic material or material that is potentially offensive. See also mailing list, moderator, newsgroup.

moderator

n. In some Internet newsgroups and mailing lists, a person through whom all messages are filtered before they are distributed to the members of the newsgroup or list. The moderator discards or edits any messages that are not considered appropriate. See also mailing list, newsgroup.

modified frequency modulation encoding

n. Abbreviated MFM encoding. A widely used method of storing data on disks. MFM encoding is based on an earlier technique called frequency modulation encoding but improves on its efficiency by reducing the need for synchronizing information and by basing the magnetic coding of each bit on the status of the previously recorded bit. MFM encoding stores more information on a disk than does frequency modulation encoding and is used on many hard disks. It is not, however, as efficient a space saver as the technique known as run-length limited encoding, or RLL. Compare frequency modulation encoding, run-length limited encoding.

modifier key

n. A key on the keyboard that, when held down while another key is pressed, changes the meaning of the keystroke. See also Alt key, Command key, Control key, Shift key.

modular design

n. An approach to designing hardware or software. In modular design, a project is broken into smaller units, or modules, each of which can be developed, tested, and finished independently before being combined with the others in the final product. Each unit is designed to perform a particular task or function and can thus become part of a "library" of modules that can often be reused in other products having similar requirements. In programming, for example, one module might consist of instructions for moving the cursor in a window on the screen. Because it is deliberately designed as a stand-alone unit that can work with other sections of the program, the same module might be able to perform the same task in another program as well, thus saving time in development and testing.

module

n. 1. In programming, a collection of routines and data structures that performs a particular task or implements a particular abstract data type. Modules usually consist of two parts: an interface, which lists the constants, data types, variables, and routines that can be accessed by other modules or routines, and an implementation, which is private (accessible only to the module) and which contains the source code that actually implements the routines in the module. See also abstract data type, information hiding, Modula-2, modular programming. 2. In hardware, a self-contained component that can provide a complete function to a system and can be interchanged with other modules that provide similar functions. See also memory card, SIMM.

monitor

n. The device on which images generated by the computer's video adapter are displayed. The term monitor usually refers to a video display and its housing. The monitor is attached to the video adapter by a cable. See also CRT.

monochrome

adj. Of, pertaining to, or being a monitor that displays images in only one color--black on white (as on early monochrome Macintosh screens) or amber or green on black (as on early IBM and other monochrome monitors). The term is also applied to a monitor that displays only variable levels of a single color, such as a gray-scale monitor.

monochrome adapter

n. A video adapter capable of generating a video signal for one foreground color or sometimes for a range of intensities in a single color, as for a gray-scale monitor.

monochrome display

n. 1. A video display capable of rendering only one color. The color displayed depends on the phosphor of the display (often green or amber). 2. A display capable of rendering a range of intensities in only one color, as in a gray-scale monitor.

Monochrome Display Adapter

n. See MDA.

monographics adapter

n. Any video adapter that can display only monochrome text and graphics; any video adapter functionally compatible with the Hercules Graphics Card (HGC). See also HGC.

monospace font

n. A font (set of characters in a particular style and size), similar to that used on a typewriter, in which each character occupies the same amount of horizontal space regardless of its width--an i, for example, taking as much room as an m. This is a sentence in a monospace font. Also called fixed-width font. See also monospacing. Compare proportional font.

MOO

n. Acronym for MUD, object oriented. A form of multi-user dungeon (MUD) that contains an object-oriented language with which users can create areas and objects within the MOO. Generally, MOOs are more focused on communications and programming and less on games than MUDs are. See also MUD.

MooV

n. The file format for QuickTime movies that stores synchronized tracks for control, video, audio, and text. See also QuickTime.

morphing

n. Short for metamorphosing. A process by which one image is gradually transformed into another, creating the illusion of a metamorphosis occurring in a short time. A common motion picture special-effects technique, morphing is available in many advanced computer animation packages. See also tween.

Mosaic

n. The first popular graphical World Wide Web browser. Released on the Internet in early 1993 by the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign, Mosaic is available as freeware and shareware for Windows, Macintosh, and X Window systems. Mosaic is distinguished from other early Web browsers by its ease of use and its addition of inline images to Web documents. Also called NCSA Mosaic.

Most Recently Used List

n. In an application, a listing of the last files that have been saved or loaded in chronological order (the last file saved or opened appears first). Typically appears at the bottom of the File menu. Acronym: MRU.

most significant bit

n. In a sequence of one or more bytes, the highest-order bit of a binary number, not including the sign bit. See also high-order. Compare least significant bit. Acronym: MSB.

motherboard

n. The main circuit board containing the primary components of a computer system. This board contains the processor, main memory, support circuitry, and bus controller and connector. Other boards, including expansion memory and input/output boards, may attach to the motherboard via the bus connector. See also expansion slot. Compare daughterboard.

Motion JPEG

n. A standard for storing motion video, proposed by the Joint Photographic Experts Group (JPEG), that uses JPEG image compression for each frame. See also JPEG (definition 1). Compare MPEG (definition 1).

mount

vb. To make a physical disk or tape accessible to a computer's file system. The term is most commonly used to describe accessing disks in Apple Macintosh and UNIX-based computers.

mouse

n. A common pointing device. The basic features of a mouse are a flat-bottomed casing designed to be gripped by one hand; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk top), the user typically controls an on-screen cursor. A mouse is a relative pointing device because there are no defined limits to the mouse's movement and because its placement on a surface does not map directly to a specific screen location. To select items or choose commands on the screen, the user presses one of the mouse's buttons, producing a "mouse click." See also bus mouse, mechanical mouse, optical mouse, optomechanical mouse, relative pointing device, serial mouse. Compare trackball.

MouseKeys

n. A feature in Microsoft Windows that allows a user to use the numeric keyboard to move the mouse pointer. MouseKeys is primarily intended for people who may have physical limitations that make it difficult to move a conventional mouse. See also mouse.

mouse pad

n. A surface on which a mouse can be moved, typically a rectangular rubber pad covered with fabric, providing more traction than a wooden or glass desktop or tabletop. See also mouse.

mouse pointer

n. An on-screen element whose location changes as the user moves the mouse. Depending on the location of the mouse pointer and the operation of the program with which it is working, the area of the screen where the mouse pointer appears serves as the target for an action when the user presses one of the mouse buttons. See also block cursor, cursor (definition 3).

mouse trails

n. The creation of a shadowlike trail following the mouse pointer on screen in order to make it easier to see. Mouse trails are useful for laptops and notebooks, particularly ones with passive matrix displays or older models with monochrome screens. The relatively low resolution and contrast of these screens made it easy to lose sight of a small mouse pointer. See also mouse pointer, submarining.

move

n. A command or instruction to transfer information from one location to another. Depending on the operation involved, a move can affect data in a computer's memory or it can affect text or a graphical image in a data file. In programming, for example, a move instruction might transfer a single value from one memory location to another. In applications, on the other hand, a move command might relocate a paragraph of text or all or part of a graphic from one place in a document to another. Unlike a copy procedure, which duplicates information, a move indicates that information either is or can be deleted from its original location. Compare copy.

Moving Pictures Experts Group

n. See MPEG (definition 1).

Mozilla

n. A nickname for the Netscape Navigator Web browser, coined by the Netscape Corporation. See also Mosaic, Netscape Navigator.

MPC

n. See Multimedia PC.

MPEG

n. 1. Acronym for Moving Pictures Experts Group. A set of standards for audio and video compression established by the Joint ISO/IEC Technical Committee on Information Technology. The MPEG standard has different types that have been designed to work in different situations. Compare Motion JPEG. 2. A video/audio file in the MPEG format. Such files generally have the extension .mpg. See also JPEG. Compare Motion JPEG.

MPEG-1

n. The original MPEG standard for storing and retrieving video and audio information, designed for CD-ROM technology. MPEG-1 defines a medium bandwidth of up to 1.5 Mb/s, two audio channels, and noninterlaced video. See also MPEG (definition 1). Compare MPEG-2, MPEG-3, MPEG-4.

MPEG-2

n. An extension of the MPEG-1 standard designed for broadcast television, including HDTV. MPEG-2 defines a higher bandwidth of up to 40 Mb/s, five audio channels, a wider range of frame sizes and interlaced video. See also HDTV, MPEG (definition 1). Compare MPEG-1, MPEG-3, MPEG-4.

MPEG-3

n. Initially an MPEG standard designed for HDTV (high-definition television), but it was found that MPEG-2 could be used instead. Therefore, this standard no longer exists. See also HDTV, MPEG (definition 1). Compare MPEG-1, MPEG-2, MPEG-4.

MPEG-4

n. A standard currently under development designed for videophones and multimedia applications. MPEG-4 provides a lower bandwidth of up to 64 Kb/s. See also MPEG (definition 1). Compare MPEG-1, MPEG-2, MPEG-3.

MPPP

n. See Multilink Point-to-Point Protocol.

mput

n. In many FTP clients, the command that instructs the local client to transmit multiple files to the remote server.

MR

n. Acronym for modem ready. A light on the front panel of a modem indicating that the modem is ready.

MRU list

n. Short for Most Recently Used list.

ms

n. See millisecond.

MS-DOS

n. Acronym for Microsoft Disk Operating System. A single-tasking, single-user operating system with a command-line interface, released in 1981, for IBM PCs and compatibles. MS-DOS, like other operating systems, oversees operations such as disk input and output, video support, keyboard control, and many internal functions related to program execution and file maintenance.

MS-DOS mode

n. A shell in which the MS-DOS environment is emulated in 32-bit systems such as Windows 95. See also MS-DOS, shell¹.

MS-DOS shell

n. A shell environment based on a command line prompt that allows a user to interact with MS-DOS or an MS-DOS-emulating operating system.

MSDOS.SYS

n. One of two hidden system files installed on an MS-DOS startup disk. MSDOS.SYS, called IBMDOS.SYS in IBM releases of MS-DOS, contains the software that makes up the heart (kernel) of the operating system. See also IO.SYS.

msec

n. See millisecond.

MTBF

n. Acronym for mean time between failures. The average time interval, usually expressed in thousands or tens of thousands of hours (sometimes called power-on hours or POH), that will elapse before a hardware component fails and requires service.

MTTR

n. Acronym for mean time to repair. The average time interval, usually expressed in hours, that it takes to repair a failed component.

MUD

n. Acronym for multi-user dungeon. A virtual environment on the Internet in which multiple users simultaneously participate in a role-playing game and interact with each other in real time. Also called multi-user simulation environment.

multifunction board

n. A computer add-in board that provides more than one function. Multifunction boards for personal computers frequently offer additional memory, serial/parallel ports, and a clock/calendar.

multi-hosting

The ability of a web server to support more than one Internet address and more than one home page. Also called multi-homing.

Multilink Point-to-Point Protocol

n. An Internet protocol that allows computers to establish multiple physical links to combine their bandwidths. This technology creates a virtual link with more capacity than a single physical link. See also PPP. Acronym: MPPP.

multimedia

n. The combination of sound, graphics, animation, and video. In the world of computers, multimedia is a subset of hypermedia, which combines the aforementioned elements with hypertext. See also hypermedia, hypertext.

Multimedia PC

n. Software and hardware standards set forth by the Multimedia PC Marketing Council, which sets minimum standards for a PC's sound, video, and CD-ROM playing capabilities. Acronym: MPC.

Multimedia Personal Computer

n. See Multimedia PC.

multiplexer

n. 1. A hardware circuit for selecting a single output from multiple inputs. 2. A device for funneling several different streams of data over a common communications line. Multiplexers are used to attach many communications lines to a smaller number of communications ports or to attach a large number of communications ports to a smaller number of communications lines. Acronym: MUX.

multiplexing

n. A technique used in communications and input/output operations for transmitting a number of separate signals simultaneously over a single channel or line. To maintain the integrity of each signal on the channel, multiplexing can separate the signals by time, space, or frequency. The device used to combine the signals is a multiplexer. See also FDM, space-division multiplexing, time-division multiplexing.

Multi-Protocol Over ATM

n. See MPOA.

Multipurpose Internet Mail Extensions

n. See MIME.

multiuser

n. See multiuser system.

multiuser dungeon

n. See MUD.

multiuser simulation environment

n. See MUD.

MUX

n. See multiplexer (definition 2).

My Briefcase

n. A Windows 95 utility, helpful for workers away from the office, that manages the updating of modified files once the remote user's computer is connected back on the office network.

MYOB