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Mainframe Computer - A large and fast computer system that multiple users can share data and run multiple applications. Mainframe computers are excellent at moving large amounts of data around in database applications. Examples are:- Bull, IBM, Borough and Cray. A popular example of their operating system is the MVS. Early examples were housed and filled in a specially air conditioned room, however later examples can be smaller than the average persons wardrobe. See also Database and Operating Systems.

Main Board - See also Motherboard.

Megabyte - The size of working memory or backing storage. Mb, or Megabytes or Meg for short meaning approximately one million characters (1048576 bytes to be exact or 1024 Kilobytes).

Memory - This is the working store that software programs are loaded into and their instructions executed on your processor(s). Data is also held in memory and manipulated by these programs. Memory is measured in bytes, and a byte can hold a character of information, i.e. a letter in a word. Modern computers may measure the size of their memory in Mb, or Megabytes or Meg for short meaning approximately one million characters (1048576 to be exact). Memory is volatile which means that programs and data will be lost if the computer is switch off unless these are first written to some form of storage device, i.e. disc or tape. See Storage Devices, Kilobyte, Megabyte and Gigabyte.

Metadata - The description of what type of data is contained in a document or file. Used on web-sites so that search engines can determine the type of data stored there. See also File, Web-Site and Search Engine.

Metafile - An image composed of a set of drawing instructions, a vector graphics file.

Metatag - The header description in metadata. See also Metadata.

Microsoft - A global software and operating system company based in the USA. See also Software, Operating System and Windows.

Micro Channel - A rival to the EISA standard by IBM. IBM never released the specification to third party expansion card manufacturers in an attempt to capture the expansion card market. Expansion card manufacturers invested in the rivals ISA/EISA the successor to ISA and later PCI. See also Interface, Motherboard, AGP, PCI, ISA, EISA, VLB and Micro channel.

Micro Computer - Named also the "Micro" and now archaic. Originally in the early eighties, these were the smallest computers that could be purchased. Early examples were:- ZX Spectrum, Acorn Electron, Acorn BBC A/B, Commodore, Atari and Sharp. These used their own proprietary operating systems and so data conversion between them was not easy or popular. The advent of the Personal Computer design from IBM and the distribution of the MS-DOS operating system made the PC the more popular choice for business use.

MIDI - Musical Instrument Digital Interface. A method to exchange data between a computer and a musical synthesiser or instrument. An expansion sound card will have a MIDI interface. See also Data and Sound Card.

Millennium Bug - See also Year 2000 bug.

Mini Computer - No quite as large as a Mainframe, but with the sizes of Mainframes becoming smaller and the power of Mini Computers becoming larger, the division has become a grey area, especially since Mini Computers are usually supplied by the same vendors as Mainframes. See also Mainframe.

MMX - Multi Media Extensions. A range of extra processor instructions developed by Intel and first included on their Pentium processor. These extra instructions speed up the processing on desktop multi media computer systems but no advantage to server type systems. See also Processor, Multi Media, Desktop (Workspace) and Server.

Modem - Short for Modulator/Demodulator. The process of converting digital signals into analogue frequencies (or tones) suitable for transmission over a voice telephone line is called modulating. A zero would be represented as frequency A, for example 4KHz and a one would be represented as frequency B, for example 6KHz. As bits are sequentially fed into the modem at one end, sounds or tones are emanated or "played" over the telephone line. A modem at the receiving computer will listen to these tones and convert them back into the bits stream. This opposite process is called demodulating. For the process to be two way, both the modulation and demodulation electronics are fitted in the modem device. Modern computers will use a modem to connect to your Internet service providers computer(s) which are connected to the Internet. See also bit and Internet.

Modulation - The method of converting digital data to an analogue signal for the purpose of transmission over telephone a line by using ADC and DAC principles. The device responsible for this usually is a modem, short for modulator/demodulator. See also Data, Modem, ADC and DAC.

Monitor - The television like unit that displays the text and graphical output on your computer.

Motherboard - Some times known as the system board or main board. All the components and devices of the computer must be interconnected by some electrical connections. Essentially the motherboard does just that. It interconnects all the chips and devices by plugs, slots, sockets etc. and provides all the chips that are need to perform this interconnection. This interconnection chip logic is also known as the chipset. See also Devices and Chipset.

Mouse - The input device that is used to represent a graphical position of a pointer in a computer system with a GUI Graphics User interface. A mouse may have one or more buttons on it that the user can click to select objects on the screen. See also GUI.

Multimedia - A computer that has a sound card, CD-Drive and possibly a modem or DVD Drive and a high resolution colour graphics adapter and monitor. A multimedia computer would usually be found in the home for playing games software or surfing the Internet. See also Sound Card, CD-Drive, DVD Drive, Modem, Resolution, Graphics Adapter, Monitor and Internet.

Multitasking - The ability for an operating system to be able to run more than one program at the same time, i.e. concurrently. See also Operating System and Program.

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