MAC ~ MILNET
A/B Switch box ~ America On-line AMI BIOS ~ Arithmetic Operation ARP ~ AVI Backbone ~ Bit Image Bit Map ~ Boot Disk Boot Drive ~ Bytes Per Inch C++ ~ Carrier Frequency carrier system ~ certification CGI ~ Chooser extension cipher ~ Clipper Chip clock ~ color color bits ~ communications satellite communications server ~ computer security CON ~ copy copy program ~ cycle time daemon ~ defragmentation demand paging ~ digitize DikuMUD ~ disk disk buffer ~ Document Style Semantics and Specification Language document window ~ dynamic Web page Easter egg ~ erase erase head ~ ezine F2F ~ finger2 firewall ~ font suitcase footer ~ FYI Game Control Adapter ~ GUI HAL ~ hot key1 hot key2 ~ Hz i486DX ~ internal modem internet ~ ISO 9660 ISO/OSI model ~ just-in-time K1 ~ knowledge base L1 cache ~ LU luggable computer ~ LZW compression MAC ~ MILNET mime ~ msec MTBF ~ MYOB named anchor ~ network drive Network File System ~ number crunching object ~ overwrite mode P5 ~ PC/XT keyboard PDA ~ pipeline processing piracy ~ preventive maintenance preview ~ pwd quasi-language ~ QWERTY keyboard R&D ~ registration marks Registry ~ RFI RF shielding ~ run-time library SAA ~ server error server push-pull ~ soft return software ~ style sheet stylus ~ System T1 ~ ToggleKeys token ~ typography UART ~ uupc V.120 ~ view2 viewer ~ VxD w3 ~ WinG WINS ~ WWW X.25 ~ X Windows Yahoo! ~ yotta- Z39.50 standard ~ Zulu time
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.
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.
A/B Switch box ~ America On-line AMI BIOS ~ Arithmetic Operation ARP ~ AVI Backbone ~ Bit Image Bit Map ~ Boot Disk Boot Drive ~ Bytes Per Inch C++ ~ Carrier Frequency carrier system ~ certification CGI ~ Chooser extension cipher ~ Clipper Chip clock ~ color color bits ~ communications satellite communications server ~ computer security CON ~ copy copy program ~ cycle time daemon ~ defragmentation demand paging ~ digitize DikuMUD ~ disk disk buffer ~ Document Style Semantics and Specification Language document window ~ dynamic Web page Easter egg ~ erase erase head ~ ezine F2F ~ finger2 firewall ~ font suitcase footer ~ FYI Game Control Adapter ~ GUI HAL ~ hot key1 hot key2 ~ Hz i486DX ~ internal modem internet ~ ISO 9660 ISO/OSI model ~ just-in-time K1 ~ knowledge base L1 cache ~ LU luggable computer ~ LZW compression MAC ~ MILNET mime ~ msec MTBF ~ MYOB named anchor ~ network drive Network File System ~ number crunching object ~ overwrite mode P5 ~ PC/XT keyboard PDA ~ pipeline processing piracy ~ preventive maintenance preview ~ pwd quasi-language ~ QWERTY keyboard R&D ~ registration marks Registry ~ RFI RF shielding ~ run-time library SAA ~ server error server push-pull ~ soft return software ~ style sheet stylus ~ System T1 ~ ToggleKeys token ~ typography UART ~ uupc V.120 ~ view2 viewer ~ VxD w3 ~ WinG WINS ~ WWW X.25 ~ X Windows Yahoo! ~ yotta- Z39.50 standard ~ Zulu time