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Micron (µm) A unit of measure equivalent to one-millionth of a metre; synonymous with micrometre

Microsecond (µs) One millionth of a second (.000001 sec.).

MAC (Media Access Control) An element of Data Link layer protocol that provides compatibility with the NIC used by the Physical layer. An adapter address is NIC used by the Physical layer. An adapter address is often called a MAC address.

Mac Macintosh: introduced by Apple Computer in 1984, the Macintosh marked a breakthrough in personal computer technology, featuring a graphical user interface (GUI) that utilised windows, icons and a mouse. This made it much easier for novices to use the computer productively, requiring them only to point to a selection on a menu and click a mouse button rather than learn a complex set of commands, as had previously been the case. The success of the Macintosh GUI led heralded a new age of graphics-based applications and operating systems, Microsoft's subsequent Windows interface copying many features from the Mac.

Macro A small sequence of commands, contained within a document, that can be automatically executed when the document is loaded, or executed later by pressing a predetermined keystroke.

Macro virus A virus that can hide in the macros of a document file. Typically, viruses do not reside in data or document file.

Make code A code produced by pressing a key, See Break code.

MB (Megabyte) 1,048,576 bytes (1,024 times 1,024). Used to describe the total capacity of a hard or floppy disk or the total amount of RAM. Sometimes abbreviated as Mb, M, MB, or meg for megabyte; and Mb, M-bit, or Mbit for megabit. When in doubt, it's probably megabyte, not megabit, with these exceptions: the capacity of a single memory chip (a 1-megabit chip; you need eight chips plus an optional ninth parity-checking chip to get 1 megabyte of memory), the throughput of a network (4 megabits per second), and the transfer speed of a hard disk (5 megabits per second).

MBps (Megabytes per second) A performance measure used for mass storage devices and memory systems.

MBR (Master boot record) The record written at the beginning of a disk, containing information about the disk as well as startup programs.

MCA bus (Micro Channel Architecture) A proprietary IBM PS/2 bus, seldom seen today, with a width of 16 or 32 bits and multiple master control, which allowed for multitasking. See also EISA.

MCI (Media Control Interface) Platform-independent multimedia specification published by Microsoft Corporation and others in 1990. Provides a consistent way to control devices such as CD-ROMs and video playback units.

MD or MKDIR command A DOS command used to create a directory on a drive (for example, MD C:\MYDATA will create a directory in drive C called MYDATA).

MDRAM (Multibank DRAM) A special kind of RAM that is able to use a full 128-bit bus path without requiring the full 4 MB of RAM.

Media A component used to store data such as a tape or rotating disk.

Mega One million, but with computers it typically means 1,048,576 (1,024 times 1,024).

MEM command A DOS utility used to display program and driver usage, as well as conventional, extended, and HMA memory (for example, MEM/C/P displays a complete listing of memory one screen at a time).

Memory A device that stores data in a computer. The term commonly used to refer to a computer system’s random access memory (RAM). The term memory has also been used to refer to all types of electronic data storage. A computer system’s memory is crucial to it’s operation; without memory, a computer cold not read programs or retain data. Memory stores data electronically in memory cells contained in chips. The two most common types of memory chips are DRAM and SRAM.

MemMaker A DOS utility that can increase the amount of conventional memory available to DOS based software applications, by loading drivers and TSRs in to upper memory.

Memory cache A small amount of faster RAM that stores recently retrieved data, in anticipation of what the CPU will retrieved data, in anticipation of what the CPU will next request, thus speeding up access.

Memory caching Using a small amount of faster RAM to store recently retrieved data, in anticipation of what the CPU will next request, thus speeding up access.

Memory conflict A problem that occurs when two programs attempt to use the same memory address at the same time. This may cause the computer to "hang."

Memory leak A problem caused when an application does not release the memory addresses assigned to it when it unloads, causing the memory addresses assigned to it when it uploads, causing the memory heaps to have less and less memory for new applications.

Memory management The process of increasing available conventional memory, required by DOS based programs, accomplished by loading device drivers and TCRs into upper memory.

Memory mapping Assigning addresses to both RAM and ROM during the boot process.

Memory paging Swapping blocks of RAM memory to an area of the hard drive to serve as memory to an area of the hard drive to serve as virtual memory when RAM memory is low.

Memory-resident virus A virus that can stay lurking in memory, even after its host program is terminated.

Mflops (Megaflops) 1 million floating-point instructions per second.

MHz (Megahertz) One million cycles per second, typically used in reference to a computer's clock rate. Both the clock rate and the processor type (80286, 80386, etc.) determine the power and speed of a computer

MiB (Mebibyte) A unit of measure consisting of 1024KiB.

Microprocessor An integrated circuit (IC) that communicates, controls, and executes machine language instructions.

Microcode The lowest-level instructions that directly control a microprocessor. A single machine-language instruction typically translates into several microcode instructions. In modern PC microprocessors, the microcode is hard-wired and can't be modified.

Middleware Software necessary for an application on a client to pass requests to a server, and for a server to respond with data. Microsoft's ODBC (Open Database Connectivity) is an example of middleware.

Minifile system InWindows NT boot process, a simplified file system that is started so that Ntldr (NT Loader) can read files from either a FAT or an NTFS file system.

MIRROR command A DOS command that can be used to save the partition table of a hard drive to a floppy disk.

MIPS (Millions of Instructions Per Second) refers to a computer processor's performance.

MMX technology (Multimedia Extensions) A variation of the Pentium processor designed to manage and speed up high-volume input/output needed for graphics, motion video, animation, and sound.

MO drives (Magneto-optical) Removable, rewritable, high-capacity drives that combine magnetic and optical disc technology.

Modem (MOdulate/DEModulate) A combination of the words modulate and demodulate. A device modulates digital data from a computer to an analog format that can be sent over telephone lines, then demodulates it back into digital form.

Modem speed The speed a modem can transmit data along a phone line measured in bits per second (bps). Two communicating modems must talk at the same speed for data transmission to be successful.

Modem-eliminator A"null modem" that allows two DTE (Data Terminal Equipment) devices to communicate by means of a special cable in which the transmit and receive wires are cross-connected.

Modulation Converting binary or digital data into an analog signal that can be sent over standard telephone lines.

Monitor The most commonly used output device for displaying text and graphics on a computer (for example, a 15-inch SVGA monitor).

Mouse A pointing and input device that allows the user to move the cursor around the screen and select programs with the click of a button.

MOPS (Millions of Operations Per Second.)

MPC specifications (Multimedia Personal Computer) The minimum standards created by Microsoft and a consortium of hardware manufacturers for multimedia PCs.

MPEG (Moving Pictures Experts Group) A processing-intensive standard for data compression for motion pictures that tracks movement from one frame to the next, and only stores the new data that has changed.

ms (Millisecond) One thousandth of a second (.001 sec.).

MSAU or MAU (Multistation access unit) A centralized hub device used to connect IBM Token Ring network ststions.

MSDOS.SYS A read-only, hidden MS-DOS system file that must be on the boot disk for a system to boot successfully.

MTBF (Mean Time Between Failure) The average time a specific component is expected to work without failure.

MTTR (Mean Time To Repair) The average time to repair a specific component.

Multiframe dialog When a token is sent that allows a receving station to communicate only with the sending station, thus providing continuous communication between the two stations.

Multimedia The presentation of information on a computer using sound, graphics, photos, animation, full-motion video, and text.

Multimeter Either a voltmeter or an ammeter that can also measure resistance in ohms or as continuity, depending on a switch setting.

Multipartite virus A combination of a boot sector virus and a file virus. It can hide either type of program.

Multiplier The factor by which the bus speed is multiplied to get the CPU clock speed.

Multiscan monitor A monitor that can work within a range of frequencies, and thus can work with different standards and video adapters. It offers a variety of refresh rates.

Multisession A CD feature that allows data to be read (or written) on a disc recorded in more than one session. This is important if the disc was only partially filled during the first write.

Multitasking The concurrent execution of several jobs.

Multithreading The ability of an application under Windows NT to pass more than one function (thread) to the kernel at the same time, such as when one thread is performing a print job while another reads a file.

MIDI (Musical Instrument Digital Interface) Pronounced "middy," a standard for transmitting sound from musical devices, such as electronic key boards, to computers where it can be digitally stored.