M

MA              See MR.
MA              Match Register. The register in an associative memory that 
                holds the result of an associative search. The match register 
                has 1 match bit for each word in the memory. During an 
                associative search, the hardware sets bit i if word i matched
                the argument.
MAC             Medium Access Control. The portion of the IEEE 802 data 
                station that controls and mediates the access of the medium.
MAC		Message Authentication Code.
MAC             Multiply ACcumulate.
Macintosh       A personal computer introduced by Apple Corporation in 1984
                that uses a 32-bit Motorola 68000 microprocessor and a
                graphical interface.
MAE             Macintosh Application Environment.
MADALINE        Many ADAptive LINear Elements.
MAN             Metropolitan Area Network. The MAN, an evolutionary step
                beyond the LAN, promises high-speed communications at
                distances greater than any LAN can handle.
MAP             Manufacturing Automation Protocol. The MAP is not itself a
                standard. Nor is it a protocol. Rather, it is a systematic
                exploration or specification of the way in which OSI
                standards can be integrated into a real open system network.
MAPI		MHS Application Program Interface.
MAR             Memory Address Register. The programmer-invisible register in
                which the computer holds the address of a reference during a
                memory access; not part of the register set.
Mark-I,II,III,IV
                Four early computers developed by Howard Aiken at Harvard
                University in the 1940s and having separate memories for
                programs and data; Mark-I and Mark-II used electromechanical
                relays rather than vacuum tubes.
MAT             Machine-Aided Translation.
MAU             Medium Attachment Unit. The portion of the Physical Layer
                between the MDI and AUI that interconnects the trunk cable to
                the branch cable and contains the electronics that send,
                receive, and manage the encoded signals impressed on and
                recovered from the trunk cable.
MBM             Magnetic Bubble Memory. A memory technology in which the bits
                are stored in a film of magnetic material as magnetic bubbles.
MBONE           Multicast backBONE.
MBR             Memory Buffer Register. A programmer-invisible buffer in
                which the computer holds data for a store operation and into
                which it receives data during a load operation; not part of
                the register set.
MBS             Megabytes Per Second. A standard unit for reporting transfer
                rates.
MC              Marginal Check.
MCA             Micro Channel Architecture. IBM's expanded-local-bus
                architecture introduced in its PS/2 family of personal
                computers.
M-CAD		Mechanical engineering Computer-Aided Design.
MCB             Memory Control Block. The data structure containing the
                length and owner (among other things) of a portion of the
                memory managed by DOS.
MCC             Microelektronics and Computer technology Corporation.
MCGA            Multi-Color Graphics Array. The low-end color adapter offered
                in IBM's early PS/2 series machines.
MCI             Media Control Interface.
MCM             MultiChip Module.
MCS-51          See 8051.
MCS             MultiChannel Communications System.
MCST            Minimum Cost Spanning Tree. An MCST has a total less than or
                equal to all other spanning trees.
MCU             Multipoint Control Unit.
MD5		Message Digest, version 5. This important hash function is 
		perhaps the most popular algorithm for providing 
		authentication and digital signatures in a variety of 
		applications.
MDA             Monochrome Display Adapter. The standard video display for
                the first IBM PC model, with one foreground color and one
                background color (e.g. green on black).
MDF             Main Distributing Frame.
MDI             Medium Dependent Interface. The mechanical and electrical
                interface between the trunk cable medium and the MAU.
MDI             Multiple Document Interface.
MDM             Manchester Dataflow Machine. The MDM is an example of a
                dynamic, tagged-token architecture.
MDP             Message-Driven Processor. A single chip, million transistor 
                VLSI microcomputer.
MDQL            MultiDimentional Query Language.
MDR             Memory Data Register. See MBR.
MDRAM           Multibank Dynamic Random Access Memory.
MDS             Microcomputer Development System.
MESI            Modified, Exclusive, Shared, Invalid.
MFC             Microsoft Foundation Class.
MFLOPS          Megaflops. A measurement of the speed of the computer,
                usually applied to scientific computers rather than general-
                purpose computers, that focuses on floating-point operations,
                rather than instruction executions.
MFM             Modified Frequency Modulation. A method of encoding data as a
                series of magnetic flux reversals on disk or tape, commonly
                known as double-density recording.  In contrast to FM,
                modified frequency modulation omits all clock pulses except
                those between pairs of zero bits.  See also FM, RLL.
MFP             MultiFunction Peripheral.
MFSET           Merge-Find SET. MFSETs are a special kind of sets
                specifically designed for these operations.
MHS             Message Handling Systems. MHS refers to the Action
                Technologies and Novell implementation of a store-and-forward
                electronic mail system. Within the LAN industry, MHS has
                become a de facto standard for linking applications with
                internetwork transport systems.
MI		Management Interface.
MIB             Management Information Base. The name of the database used to 
                hold the management information relating to a network or 
                internetwork.
MIC             Medium Interface Connector. To connect a station to the trunk
                cable, a connecting cable is attached through a MIC from the
                station to a TCU.
MIC		Message Integrity Code.
MICR            Magnetic Ink Character Recognition.
MIDI            Musical Instrument Digital Interface. A standard
                communications protocol for exchanging information between
                computers and musical synthesizers. MIDI allows interaction
                between musical instruments and computers.
MIF             Management Information File/Format.
MIMD            Multiple Instruction stream Multiple Data stream. In Flynn's
                classification, refers to computers that consist of several
                independent processors, each capable of executing a different
                program on its own set of data.
MIME            Multipurpose Internet Mail Extensions.
MI/MIC          Mode Indecate / Mode Indicate Common. Also called forced or
                manual originate. Provided for installations where other
                equipment, rather than the modem, does the dailing. In such
                installations, the modem operates in Dumb mode (no Auto Dail
                capability), yet must go off hook in originate mode to
                connect with answering modems.
                network that is composed of several stages; the data must
                traverse them in series.
MIPS            Millions of Instructions Per Second; a measure of the speed
                of the processor.
MIPS R2000      A 32-bit RISC machine (circa 1985) by MIPS Computer Systems.
MIS             Management Information System.
MISD            Multiple Instruction stream Single Data stream. In Flynn's
                classification, refers to computers that have several
                processors, each capable of executing a different program
                but operating on the same sequence of data; no computers of
                this category exist.
MISG            Motorola Information Systems Group.
MISMEA          Multiple Instruction Stream Multiple Execution Scalar.
MISMES          Multiple Instruction Stream Multiple Execution Array.
MITS            Micro Instrumentation and Technology.
MITV            Microsoft Interactive TeleVision.
M-JPEG          Moving-Joint Photografic Experts Group.
MLI             Machine Learning and Inference center.
MLID            Multiple Link Interface Driver.
MMS             Manufacturing Messaging Specification (Service). A protocol 
                entity forming part of the application layer. It is intended 
                for use specifically in the manufacturing or process control 
                industry. It enables a supervisory computer to control the 
                operation of a distributed community of computer-based 
                devices.
MMS             Microsoft Media Server.
MMU             Memory Management Unit.
MNOS            Metal-Nitride-Oxide Semiconductor.
MNP             Microcom Networking Protocol. An asynchronous error control
                protocol developed by Microcom, Inc. and now in the public
                domain. The protocol ensures error-free transmission through
                error detection (CRC) and retransmission of errored frames.
MNS FET         Metal-Nitride Semiconductor Field-Effect Transistor.
MO              Magneto-Optical.
MOB             Memory Oreder Buffer.
MODEM           MOdulator/DEModulator. A device that modulates and
                demodulates signals transmitted over communication
                facilities. A modem is sometimes called a data set.
MOL             Machine-Oriented Language.
MOM             Message-Oriented Middleware.
MOPS            Millions of Operations Per Second.
MOS             Metal-Oxide Semiconductor.
MOS FET         Metal-Oxide Semiconductor Field-Effect Transistor.
MOV             Metal-Oxide Varistor
MP-1            MasPar-1.It features an SIMD array up to 16K 4-bit processors 
                organized as a two-dimensional array with each processor 
                connected to its eight nearest neighbours.
MP-2            MasPar-2. The second generation MasPar maintains the same 
                system architecture as the MP-1 but with the processors 
                upgraded to 32-bit engines.
MPP             Massively Parallel Processor. An SIMD processor built by
                Goodyear Aerospace Corporation in the early 1980s; had up to
                16,384 1-bit processing elements.
MP-RAM          Message-Passing Random Access Memory.
MPS             Multi-Processor Specification.
MR              Magnetic Resonance.
MR              Mask Register. A register whose bits mask an operation (e.g.
                in an associative store the bits mask the fields that will
                not participate in a match; in an interrupt controller the
                bits mask interrupts and in a DMA controller the bits mask
                incoming requests for services).
MS DOS          MicroSoft corporation's Disk Operating System. Used in most
                IBM PC's and clones.
MSDB            Main Storage DataBase. An MSDB is a root-only database. It is
                kept in primary memory throughout system operation. Small
                reference tables such as conversion tables and timetables are
                good candidates for MSDBs.
MSI             Medium Scale Integration. Characteristic of integrated
                circuits having hundreds of transistors on them.
MSIMD           Multiple Single Instruction Multiple Data. See also SIMD.
MSN             MicroSoft Network.
MSP             Manual Switching Position.
MSR             Mark Sheet Reader.
MSS             Mass Storage System.
MT              Machine Translation.
MTBF            Mean Time Between Failures. A measurement of system
                reliability for a fault-tolerant system; the average
                operating time between the start of normal operation and its
                first electronic or mechanic failure.
                a fault-tolerant system; used when only one failure is
                possible, such as a component failure.
MTTR            Mean Time To Repair. A measurement of the maintainability of
                a fault-tolerant system, when the concern is speed of repair.
mPC             MicroProgram Counter. The register within a microprogrammed
                control unit that points to the next microinstruction to be
                executed.
MUX             Multiplexer. A circuit with several inputs and a single
                output that gates a selected input to the output.
MVC             Model View Controller.
MVD             MultiValued Dependency.
MVDM            Multiple Virtual DOS Machines.
MX              Mail eXchanger.
MXM             MatriX Memory.
MZ              The letters M and Z appear in numerous places in DOS (memory
                control blocks, .EXE header, etc.); the conventional
                explanation is that these are the initials of Mark Zbikowski,
                one of the principal architects of MSDOS 2.0.
