Glossary: M

This page contains glossary terms beginning with the letter M.
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Word or Term Description or Explanation
Magneto-optical a technology used to provide read-write data storage with a removable medium - it is slower than the magnetic technology of conventional hard drives, especially in writing - however, magneto-optical discs are much cheaper than the cartridges used for conventional removable hard discs
Mail exchanger a computer that handles mail for other computers
Mail gateway a computer or service that links up two or more email systems
Mail merge when you want to send the same document to many people, you can use a file which contains the basic text which is to remain constant - the changeable details are then held in a separate file - at the time of printing, the computer will insert the information, such as names and addresses, so that each letter is individually addressed
Mail server machines to which you connect to send and receive mail
Mailbomb large amounts of data being emailed to one person, repeatedly, until it kills their mail system or at least renders it unusable - usually the result of seriously breaching netiquette
Mailing list a group of people who send and receive communal email messages on a specific topic
Majordomo basically it's a set of scripts which you can download for free, and they take care of automatically adding and removing people from a mailing list - it also allows the list admin to set up various policies which it enforces - it can automatically send all postings to a moderator for review, or just postings which exceed a certain size, or only allow postings from certain addresses - it can archive lists automatically, and produce digests, which combine all the day's messages into one big email for busy lists - these are just a few of the more major things it can do
the people who write it don't provide any of the list services; you have to install it yourself if you want to use it - or you can contact an ISP who runs it on their systems, and ask them to host the list for you
you can find out more at
Mask see Transparency mask
Mb Megabyte - approximately one million bytes of computer data (actually, it is 1K × 1Kb = 220 = 1024 × 1024 = 1,048,576 bytes)
MDF Monitor Definition File - a file used in a RiscPC to specify the parameters of the various modes that can be displayed on a particular monitor, taking account of the monitor's own specific timings and capabilities
MEMC MEMory Controller - the chip used on pre-RiscPC Acorn computers to control the way the cpu and video controller accessed the computer's memory
Metapage a web page that contains links to other web pages
MHz MegaHertz or Millions of cycles per second - this is most often used to refer to the speed of a computer's processor or memory, e.g. the RiscPC 600 has a 30MHz processor which means that it can carry out 30 million program steps each second
Midi Musical Instrument Digital Interface - a defined standard for the physical link-up between musical instruments and controllers, and also the format of the data transmitted
MIME Multipurpose Internet Mail Extensions - Internet mail was originally designed to carry text messages composed of 7-bit US ASCII characters - MIME extends the format of Internet mail messages to include information about the type of data in the message (e.g. "this message is a PostScript document", "this message is a GIF image", etc.) and provides methods for encoding 8-bit data with arbitary line lengths into 7 bit printable characters with restricted line lengths, which will be carried safely through all mail systems, no matter how antiquated or restrictive they may be - MIME makes multimedia mail possible, while retaining compatibility with the existing Internet Mail distribution system - MIME is formally specified by Internet RFCs 1521 and 1522
MIPS Million Instructions Per Second - a measure of how fast a cpu is running in terms of the number of instructions it can execute each second
Mirror site an FTP server which contains the same, or similar, information as another somewhere else in the world - mirrors are often set up to lessen transcontinental downloading
MJPEG Moving Joint Photographics Expert Group - a version of the JPEG standard which is similar to the JPEG standard but uses moving images rather than still pictures - it is used to prevent the blocking which can occur with MPEG files
MMDS Multi-point Microwave Distribution System
MMX MultiMedia Extensions - a graphical enhancement technology for use by Pentium-based computers
Mnemonic a code used in an assembler to represent a machine code instruction
MNP Microcom Network Protocol - a system used by modems to provide data compression and error correction for high speed data transmission over phone lines - there are various standards of increasing speed and complexity, e.g. MNP4 and MNP5
Mode see Screen mode
Modem Abbreviation for modulator-demodulator - a device which takes a serial stream of computer data and converts it into audible tones that can be transmitted down a telephone line that was originally design for carrying voice information - it enables two computers to exchange data at a distance via the telephone system
Moderator the person who runs a conference or newsgroup - they have the responsibility of selecting which postings are used and which not
Monitortype a computer variable that determines which ranges of screen modes the computer will attempt to display on your monitor
Mosaic a PC browser for the Web
Motherboard the main circuit board of a computer is sometimes referred to as a motherboard, especially when, as in the RiscPC, many of the functional parts of the computer are on separate PCBs (sometimes called Daughterboards) that are plugged into the main or motherboard
MPC Multimedia Personal Computer - the "standard" multimedia computer used in the PC world
MPEG (1) Motion Picture Experts Group - a group of technologists who are establishing an international standard for the compression of moving video and its associated audio - MPEG compression uses information from preceding and subsequent frames to allow further compression than would otherwise be achievable
MPEG (2) a video that has been compressed using MPEG techniques
MPEG (3) Moving Picture Expert Group - a file format which was developed to cope with the large files which are generated when using cameras and placing that film on disc - it checks surrounding frames and removes parts of the picture which have not changed from the previous frame, therefore saving space - this works fine for liner displaying, but when the film needs to be edited, you can end up with black blocks in the middle of the picture where the film was not started far enough back so that the data was not read and so black squares appear - similar to pixelisation when a bit-mapped image is enlarged - MJPEG was developed to cope with this and get around it
MTBF Mean Time Between Failure - an indication of how long, on average, it will be before a machine goes wrong
MUD Multi-User Dimension (or Multi User Dungeons [and Dragons]) - a form of IRC where the participants take on a persona and do role play activities
MUG Multi-User Game
Multimedia a blend of communications elements, usually computer-based, which allow information in such forms as sound, speech, text, still pictures, moving images and animations to be presented to the user so that it can be accessed in an interactive way, the user selecting which piece(s) of information to pursue
Multiplex a frequency band carrying several channels, and sometimes additional data services, allowing a wide range of information to be carried on one signal
Multisession information stored on a PhotoCD can be added to at a later date with the appropriate (very expensive) equipment - in order to read all the information on these CDs, you need a CD-ROM drive that is multisession capable
Multisync monitor some monitors are designed (for cheapness) that only display in certain modes - others can display a range of different modes - they can synchronise onto a range of different frequency signals and are therefore called 'multisync' monitors
Multitasking an operating system like RISC OS is capable of running a number of different tasks all at the same time - this is multitasking (actually, I think it's a bit of a con: the cpu can really only do one job at a time but what it does is to do a little bit of each task every fraction of a second) - there are two basic types of multitasking: preemptive and cooperative (can anyone offer me a definition of those two?)
MUSE Multi-User Simulated Environment - place where you can interact with other users

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