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The post-1993 name for MUMPS, the Massachusetts General Hospital Utility Multiprogramming System.

medium access control, mandatory access control.

machine code:
Code expressed in a form that can be recognized and executed by the processing unit of a computer.

Pertaining to software that relies on features unique to a particular kind of computer and, therefore, may be executed only on computers of that kind.

machine discovery:
Discovery of empirical laws describing regularities in observed data by machines capable of learning. Contrast with analytic learning, conceptual clustering, and taxonomy formation.

Pertaining to software that does not rely on features unique to a particular kind of computer and, therefore, may be executed on computers of more than one kind.

machine instruction:
An instruction that can be directly executed by a computer. A machine instruction is an element of a machine language.

machine language:
An artificial language composed only of the machine instructions of a specific computer or class of computers. (Figure 2 - Hierarchy of language).

machine learning:
The process by which a functional unit improves its capability or performance by acquiring new knowledge or skills, or by reorganizing existing knowledge or skills.

machine-oriented language:
A programming language, the simple statements of which have the same or similar structure as the machine instructions of a specific computer or of a class of computers. Synonymous with computer-oriented language..

machine-readable medium:
A medium that can convey data to a given sensing device. Synonymous with automated data medium.

machine vision:
(1) The automatic acquisition and analysis of images to obtain desired data. (2) The use of computer vision by a machine. Machine vision is used in manufacturing processes, quality control, etc.

machine word:
Synonym for computer word.

MAC protocol:
medium access control protocol.

Synonym for macroinstruction.

An assembler that includes, or performs the functions of, a macrogenerator.

A statement that invokes a macrodefinition at the level of the calling programming language.

A predefined sequence of commands, statements, or instructions that replaces each corresponding invoking macroinstruction or macrocall.

A module, often part of an assembler or compiler, that replaces each macroinstruction or macrocall in a source program with the appropriate code in accordance with the corresponding macrodefinition.

An instruction that invokes a macrodefinition at the level of the calling programming language. Synonymous with macro.

(1) A programming language designed to define macrodefinitions and macroinstructions. (2) A programming language that includes macrodefinitions and macroinstructions.

macro library:
A collection of macrodefinitions available for use by a macrogenerator.

A subprogram provided in some assemblers and compilers to support macrodefinitions.

Programming using macrodefinitions and macroinstructions or macrocalls.

MAC sublayer:
medium access control sublayer.

magnetic card:
A card with a magnetizable layer on which data can be stored.

magnetic card storage:
A magnetic storage in which data are magnetically recorded on the surface of thin flexible cards.

magnetic core:
A piece of magnetic material, usually torus-shaped, used for storage.

magnetic delay line:
A delay line whose operation is based on the time of propagation of magnetic waves.

magnetic disk:
A flat circular plate with a magnetizable surface layer on one or both sides of which data can be stored.

magnetic disk storage:
A magnetic storage in which data are magnetically recorded on the flat surfaces of one or more disks which, in use, rotate around a common spindle.

magnetic disk unit:
A disk drive that contains one or more magnetic heads, and associated controls that can store on and retrieve data from magnetic disks.

magnetic drum:
A right circular cylinder with a magnetizable layer on which data can be stored.

magnetic drum storage:
A magnetic storage in which data are magnetically recorded on the surface of a magnetic drum that rotates on its axis when in use.

magnetic drum unit:
A device that contains a magnetic drum, the mechanism for moving it, magnetic heads, and associated controls.

magnetic head:
An electromagnet that can perform one or more functions of reading, writing, and erasing data on a magnetic data medium.

magnetic hysteresis loop:
A closed curve showing the relation between the magnetization force and the induction of magnetization in a magnetic substance when the magnetic field is carried through a complete cycle.

magnetic ink:
A special ink that contains particles of magnetic material suitable for printing data that is recognizable from its magnetic pattern.

magnetic ink character:
A character whose pattern of magnetic ink is sensed to enable automatic identification.

magnetic ink character reader (MICR):
An input unit that reads characters by magnetic ink character recognition.

magnetic ink character recognition (MICR):
Character recognition of magnetic ink characters.

magnetic recording:
A technique of storing data by selectively magnetizing portions of a magnetizable material.

magnetic storage:
A storage device that uses magnetic properties of certain materials. Magnetic techniques may also be combined with other techniques such as in magneto-optical storage.

magnetic strip:
A strip of magnetic material that is suitable for recording data for subsequent machine reading.

magnetic tape:
A tape with a magnetizable layer on which data can be stored.

magnetic tape cartridge:
A container holding two reels and magnetic tape that winds between them, used in storage and retrieval of analog or digital data. Synonymous with magnetic tape cassette.

magnetic tape cassette:
Synonym for magnetic tape cartridge.

magnetic tape drive:
A device for controlling the movement of magnetic tape with respect to the magnetic head. Synonymous with magnetic tape transport, tape drive, tape transport.

magnetic tape leader:
The portion of magnetic tape that precedes the beginning-of-tape marker. The leader is not necessarily magnetic.

magnetic tape storage:
A magnetic storage in which data are magnetically recorded on the surface of a tape that moves longitudinally when in use.

magnetic tape trailer:
The portion of magnetic tape that follows the end-of-tape marker. The trailer is not necessarily magnetic.

magnetic tape transport:
Synonym for magnetic tape drive.

magnetic tape unit:
A device containing a magnetic tape drive, magnetic heads, and associated controls. Synonymous with tape unit.

magnetic thin film:
A layer of magnetic material, usually less than one micron thick, often used for data storage.

magnetographic printer:
A nonimpact printer that creates, by means of magnetic heads operating on a metallic drum, a latent image which is then made visible by a toner and transferred and fixed on paper.

magneto-optical disk:
A rewritable optical disk providing for data to be written as marks in the form of magnetic domains in the recording layer and erased from it using the thermo-magnetic effect, and read using the magneto-optical Kerr effect. Synonymous with MO disk.

The ratio of the length of a line in the image plane to the length of the corresponding line in the object plane.

A functional unit that contains stored messages for a specific user. A mailbox can hold either incoming or outgoing electronic mail or both. Synonymous with electronic mailbox.

mail broadcaster:
Synonym for mail exploder.

mail exploder:
A functional unit that replicates a message as required and routes the resulting copies to various recipients indicated by a distribution list. Synonymous with mail broadcaster.

mail gateway:
A functional unit that connects two or more dissimilar message handling systems and transfers messages between them.

main control unit:
In a processor with more than one instruction control unit, that instruction control unit to which, for a given interval of time, the other instruction control units are subordinated. In an operating system, an instruction control unit may be designated as the main control unit by hardware, by software, or both.

A computer, usually in a computer center, with extensive capabilities and resources to which other computers may be connected so that they can share facilities.

main memory:
Synonym for main storage.

main program:
The first module of a program to be executed and that may invoke the execution of other modules. (Figure 11 - Call graph).

main storage:
That part of internal storage into which instructions and other data must be loaded for subsequent execution or processing.

A measure of the ease with which maintenance of a functional unit can be performed using prescribed procedures and resources. Synonymous with serviceability.

maintainability performance:
The ability of a functional unit, under given conditions of use, to be retained in, or restored to, a state in which it can perform a required function when maintenance is performed under stated conditions and using stated procedures and resources.

A set of activities intended to keep a functional unit in, or to restore it to, a state in which it can perform a required function. Maintenance includes activities such as tests, measurements, replacements, adjustments, and repairs.

maintenance hook:
A trapdoor in software that allows easy maintenance and development of additional features and that may allow entry into the program at unusual points or without the usual checks.

maintenance panel:
A part of a unit of equipment that is used for interaction between the equipment and a maintenance engineer.

A logic operator having the property that if P is a statement, Q is a statement, R is a statement, then the majority of P, Q, R is True if more than half the statements are True, False if half or less are True.

majority gate:
A gate that performs a majority operation. For Boolean variables assuming values of 0 or 1, a majority gate outputs a value 1 if and only if the number of its inputs having the value 1 is greater than the number of inputs having the value 0.

majority operation:
A threshold operation in which each of the operands may take only the values 0 and 1, and the result takes the value 1 if and only if the number of operands having the value 1 is greater than the number of operands having the value 0.

The act of functioning abnormally or imperfectly.

malicious logic:
A program implemented in hardware, firmware, or software, and whose purpose is to perform some unauthorized or harmful action; for example: a logic bomb, a Trojan horse, a virus, a worm.

metropolitan area network.

managed object:
In networking, a resource that may be managed through the use of management protocols.

management domain (MD):
In networking, a set of managed objects, to which a common management policy applies. A management domain may correspond to an organization, or to a geographical area (such as a country-oriented domain), or may be international in scope, such as the function-oriented domains of "com", "edu", "mil", "net", and "org". The managing organization is particularly responsible for the administration of the addressing scheme in this set of messaging systems.

management domain name:
The identifier of a management domain. (Figure 65 - Selected O/R address attributes).

management information system (MIS):
An information processing system that supports decision-making by the management of an organization.

Manchester encoding:
A binary phase encoding in which the time interval assigned to each bit is divided in half by a transition whose direction determines the value of the bit. The transition may occur between two states of a physical variable such as voltage, magnetic polarity, or light intensity. If the physical variable is electrical, Manchester encoding is polarity-dependent but is free of a DC component. (Figure 20 - Manchester and differential Manchester encoding).

mandatory access control (MAC):
In computer security, a means of restricting access to objects, based on the sensitivity, as represented by a sensitivity label, of the information contained in the objects and the formal authorization or security clearance of subjects to access information of that sensitivity, and enforced by the trusted computing base. Contrast with discretionary access control.

manipulating industrial robot:
An automatically controlled, reprogrammable, multipurpose, manipulative machine with several degrees of freedom, which may be either fixed in place or mobile for use in industrial automation applications. The terms "fixed robot" and "mobile robot" are sometimes used to refer to manipulating industrial robots.

manipulation detection:
A procedure that is used to detect whether data have been modified, either accidentally or intentionally. Synonymous with modification detection.

manipulation detection code (MDC):
A bit string that is a function of data to which it is attached to allow manipulation detection. The resulting message (data plus MDC) may then be encrypted in order to achieve secrecy or data authentication. Synonymous with modification detection code.

The nonnegative fractional part of the representation of a logarithm.

manual answering:
Answering in which a call is established only if the called user indicates a readiness to receive the call by means of a manual operation.

manual calling:
In a data network, calling that permits the entry of selection signals from a calling data station into the line at an undefined character rate. The characters may be generated at the data terminal equipment or the data-circuit terminating equipment.

manual function:
A function initiated or effected by an operator.

manual input:
The entry of data by hand into a device.

manufacturing cell:
A manufacturing unit composed of a number of workstations, materials, storage facilities, and transport mechanisms that interconnect them.

manufacturing message service (MMS):
An application service element that enables a supervisory computer to control the operation of a distributed community of computer-based devices in a network used for manufacturing or process control.

manufacturing resource planning (MRP):
The implementation of management plans that evaluate and predict the demand for each element in the manufacturing process at a given time.

(1) A set of values that have a defined correspondence with the values or quantities of another set. (2) To establish a set of values, as in (1); for example, in the evaluation of a mathematical function, to establish the values of the dependent variable of the function, for those values of the independent variable or variables that are of immediate concern.

In computer graphics, a transformation from one coordinate system to another.

memory address register.

In text processing, a generally unused area that lies between the text area of a page or screen and any of the four edges of the page or screen. Margins may contain elements such as page headers, page footers, small illustrations, notes, and page numbers.

margin-adjust zone:
In text processing, an area generally five to seven characters wide, in which the right margin is set through hyphenation or carry-over to the next line. Synonymous with line-end zone, line-ending zone.

marginal check:
Synonym for marginal test.

marginal test:
A maintenance technique in which certain operating conditions are varied about their nominal values in order to detect or to locate potential faults. Synonymous with marginal check.

In computer security, to add one or more sensitivity designators to data.

Markov process:
A stochastic process consisting of a series of states in which the probability of transition from one state to another depends only on the two states and not on preceding states.

mark scanning:
The automatic optical sensing of marks recorded on a data medium. Synonymous with optical mark reading.

Text added to the data of a document to convey information about the document; for example: tags, processing instructions, and hyperlinks.

markup language:
(1) A text-formatting language designed to transform raw text into structured documents, by inserting procedural and descriptive markup into the raw text. (2) A language designed to describe or transform in space or time data, text, or objects into structured data, text, or objects, for example: SGML, HTML, VRML.

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