m. See meter.
MAC. (1.) See medium access control. (2.) Mandatory Access Control.
machine execution state. A state that indicates the machine is shut down, booting, or running. This state is one of two machine states.
machine instruction. (1.) A binary number that directs the operation of a processor. Compilers and assembler convert source instructions to machine instructions. (2.) An instruction of a machine language. Synonym for computer instruction and computer language.
machine language. A language that can be used directly by a computer without intermediate processing. The final output of the compilation process is a load module containing machine language instructions. Synonym for computer language.
machine object. An entry in the Network Installation Management database that represents a machine configuration.
machine state. A state that identifies the machine execution state and control state for each machine.
machine word. Synonym for word. See also computer language.
macro. (1.) A label that is declared at the start of a program or file. The label can then be used to represent the values assigned to the label in the declaration. (2.) A name or label used in place of a number of other names. (3.) The sequence of instructions or statements that a macrogenerator runs when replacing a macro instruction. (4.) A set of statements defining the name of, format of, and conditions for generating a sequence of assembler statements from a single source statement. (5.) A series of Ada-language debugger commands that execute in sequence when you call the macro. With the macro option, you can define and manipulate new debugger commands. See also routine, statement function, and subroutine.
macro call. A single instruction that, when executed, causes the execution of a predefined sequence of instructions in the same source language.
macro instruction. See macro call and macro.
macro processor. A program that converts macro instructions into specified values.
magic number. A numeric or string constant in a file that indicates the file type.
mail. Correspondence in the form of messages transmitted between workstations over a network. Synonymous with electronic mail.
mail box. A storage location in a network to which messages for a user are sent.
mail drop. The file into which messages are first received.
Mailer. In CDE, an application that enables you to send, receive, and compose electronic mail messages.
mailer. The program that does the actual delivery of mail.
mailer container. In CDE, the electronic mail box and filing system that contains all mail messages. Once a message is put in a container, you can display, modify, delete, print, include, forward, and reply to it.
Mailer control. In CDE, the Front Panel control used to start the Mailer software application. Dropping a file on the control loads the file into the Mailer Compose window.
main. In FORTRAN, the default name given to a main program if one was not supplied by the programmer.
main function. A function that has the identifier main. Each C language program must have exactly one function named main. This function is the main program of a C language program.
Main Panel. In CDE, the portion of the Front Panel excluding the subpanels.
main program. (1.) The first program unit to receive control when a program is run. Contrast with subprogram. (2.) A program that performs primary functions, passing control to routines and subroutines for the performance of more specific functions.
main storage. (1.) Program-addressable storage or memory from which instructions and other data can be loaded directly into registers for subsequent running or processing. Synonymous with system memory. (2.) The part of internal storage into which instructions and other data must be loaded for running or processing. (3.) The part of the processing unit where programs are run.
mainframe. A large computer, particularly one to which other computers can be connected so that they can share facilities the mainframe provides. The term usually refers to hardware only.
maintenance analysis procedure (MAP). Documentation used by customer engineers and by service representatives to repair equipment. A MAP contains yes/no questions and procedures that direct the user to the failing part of the equipment.
maintenance level update. The service updates (fixes and enhancements) that are necessary to upgrade the Base Operating System (BOS) or an optional software product to the current release level. See also service update.
maintenance mode. State in which a product or system can be serviced. Synonymous with service mode.
maintenance system. A special version of the operating system that is loaded from diskette and used to perform system management tasks.
major device number. A system identification number for each device or type of device. The major device, minor device, and channel numbers uniquely identify a hardware device. See also minor device number.
managed children. In Enhanced X-Windows, children in which the managed field has a value of True can have their layout (geometry) changed so that they can be repositioned and resized.
managed window. See managed children.
manager. See device manager.
Manager class. In AIXwindows, a metaclass that provides the resources and functionality to implement certain features, such as a keyboard interface and traversal mechanism. It is built from the Core, Composite, and Constraint classes.
mangling. The encoding, during compilation, of C++ identifiers such as function and variable names to include type and scoping information. The linker uses these mangled names to ensure type-safe linkage.
manual call. In data communications, a line type that requires the operator to place a call over a switched line. Contrast with auto-call.
manual dialing. In making an ATE connection, dialing the number manually over a telephone line.
map. See mapping.
MAP. See maintenance analysis procedure.
mapped. In Enhanced X-Windows, a window is said to be mapped if a map call has been performed on it.
mapped conversation. A temporary connection between an application program and an advanced program-to-program communication (APPC) session in which the system provides all the protocol information. It allows the two programs to exchange data records of any length and in any format specified by the transmission programs. Only LU6.2 sessions allow mapped conversation; it is used primarily for application transaction programs. Contrast with basic conversation.
mapped file. (1.) A file that can be accessed through direct memory operations instead of being read from disk each time it is accessed. (2.) A file on the fixed disk that is accessed as if it is in memory.
mapping. (1.) In Enhanced X-Windows, a window on which a map call has been performed. Mapping makes a window visible if there are no obscuring or occluding windows. (2.) A list, usually in a profile, that establishes a correspondence between items in two groups. For example, a keyboard mapping can establish what character is displayed when a certain key is pressed. See also keyboard mapping and profile.
margin. Left and right border of text on a screen or hardcopy page.
mark block. In Pascal, a dynamic block header that designates a subheap within a heap.
marker. (1.) A visual symbol within a non-interactive pane indicating the location of the cursor when the pane was last interactive. (2.) In computer graphics, a glyph with a specified appearance that is used to identify a particular location.
marshal. In NCS, to copy data into a Remote Procedure Call (RPC) packet. Stubs perform marshalling. Contrast with unmarshal. See also stub.
mask. (1.) A pattern of characters that controls the keeping, deleting, or testing of portions of another pattern of characters or bits, usually through an AND or OR operation. (2.) To apply a mask.
master. The only machine in the NIM environment that has permission to remotely execute commands on other NIM clients.
master dump table. A structure containing dump table entries generated by kernel components. The dump program uses this table to locate data structures that should be included in a dump.
master file. (1.) A collection of permanent information, such as a customer address file. (2.) A file that is used as an authority in a given job and that is relatively permanent, even though its contents may change.
master processor. The first processor started at boot time in a multiprocessor system.
master server. In a network installation environment, the server that has permissions to execute commands on all other machines in the environment. The master server is designed to manage the network, client, and resource objects in the network installation database.
matrix. (1.) A rectangular array of elements arranged in rows and columns that can be manipulated based on matrix algebra rules. (2.) In computers, a logic network in the form of an array of input and output leads with logic elements joined at some of their intersections. (3.) By extension, an array of any number of dimensions.
matrix stack. In GL, a stack of matrices with hardware and software support. The top matrix on the stack is the current transformation matrix, and all points passed through the graphics pipeline are multiplied by that matrix. It is a concatenation of the current modeling and viewing transformations. See also current transformation matrix.
maximum transfer unit (MTU). (1.) The maximum number of bytes that an Internet Protocol (IP) datagram can contain. (2.) The largest amount of data that can be transmitted in a single frame for a particular network interface.
M-bit. In X.25 communications, the bit in a data packet that indicates that there is more data to follow in another data packet (when a message is too large for one packet).
mbuf. A small (256-byte) buffer provided by the mbuf management facility to the various layers of communication software in the operating system.
M-byte. See megabyte.
MC. See MCU.
MCU (MC). Memory control unit.
medium access control. In a local area network, the protocol that governs communication on the transmission medium without concern for the physical characteristics of the medium. However, it takes into account the topological aspects of the network, to enable the exchange of data between data stations. See also logical link control.
megabyte (MB). Loosely, one million bytes. When referring to semiconductor memory capacity, two to the twentieth power; 1 048 576 in decimal notation. When referring to media device storage, a megabyte is ten to the sixth power (1 000 000).
megahertz (MHz). A unit of measure of frequency. One megahertz equals 1 000 000 hertz.
member. (1.) A data object in a structure, a union, or a library. (2.) Synonym for element. (3) A C++ data object or function in a structure, union or class. Members can also be classes, enumerations, bit fields and type names.
member function. C++ Operators and functions that are declared as members of a class. A member function has access to the private and protected data members and member functions of an object of its class. Member functions are also called methods.
memory. (1.) Program-addressable memory from which instructions and other data can be loaded directly into registers for subsequent running or processing. (2.) Memory on electronic chips. Examples of memory are random access memory, read-only memory, or registers. See also storage.
memory deallocation. To free up memory that has been previously allocated for a specific purpose.
memory dump. The means by which the computer system records its state at the time of a failure.
memory image. The logical layout of the parts of a process in memory.
memory leak. A software bug in which the program allocates memory, loses track of it, and then allocates some more. If the program is long-running, it can eventually tie up large amounts of real memory and paging space. System performance gradually deteriorates; the program that finally fails due to lack of resource may not be the culprit. Memory leaks in kernel extensions that allocate pinned memory may be particularly costly.
memory load control. A VMM facility that detects memory over-commitment and temporarily reduces the number of running processes, thus avoiding thrashing.
memory over-commitment. A condition in which the number of virtual-memory pages being used by the currently running programs exceeds the number of real-memory page frames available to hold them. If the over-commitment is large or sustained, system performance suffers.
menu. A displayed list of items from which an operator can make a selection.
menu bar. A rectangular area at the top of the client area of a window that contains the titles of the standard pull-down menus for that application.
menu cursor. In AIXwindows, the cursor defined for a particular menu. Each type of cursor is identified by an ID number.
menu pane. The physical window containing a pop-up menu listing a group of options to be chosen by the user. See also pane.
menu system. An interactive interface that lists related software options in a manner that expedites review and selection by the user.
message. (1.) Information from the system that informs the user of a condition that may affect further processing of a current program. (2.) An error indication, or any brief information that a program writes to standard error or a queue. (3.) Information sent from one user in a multiuser operating system to another. (4.) A general method of communication between two processes. (5.) A group of characters and control bit sequences transferred as an entity. (6.) One or more linked blocks of data or information, with associated STREAMS control structures containing a message type. Messages are the only means of communicating within a stream.
message control block. In the X.25 API, the structure used to indicate what type of packet has arrived and to point to the structure that contains the packet information.
message queue. A linked list of messages connected to a QUEUE.
message queue ID (msqid). An identifier assigned to a message queue for use within a particular process. It is similar in use to a file descriptor of a file.
message type. A defined set of values identifying the contents of a message.
metaclass. (1.) In AIXwindows and Enhanced X-Windows, an object class that does not instantiate widgets or gadgets but is capable of passing a unique set of inheritable resources to the subclasses beneath it in the class hierarchy. Each instance of a widget subclass has the features common to that widget class and exports these features to child widgets of that class. Included in this class are Core, Composite, Constraint, Primitive, Button, Manager, MenuMgr, and MenuPane. (2.) In SOM, a class whose instances are classes. In SOM, any class descended from SOMClassis a metaclass. The methods a class inherits from its metaclass are sometimes called class methods (in Smalltalk) or factory methods (in Objective-C) or constructors. See also class method.
metaclass incompatibility. In SOM, a situation where a subclass does not include all of the class variablesor respond to all of the class methods of its ancestor classes. This situation can easily arise in OOP systems that allow programmers to explicitly specify metaclasses, but is not allowed to occur in SOM. Instead, SOM automatically prevents this by creating and using derived metaclasses whenever necessary.
metadata. The structural data associated with the file system, such as the organization of directories, inode tables, and links. Metadata is not data supplied by a user; it is information about the structure of user data.
meter (m). A linear measurement that equals 1.0936 yards, 3.2808 feet, or 39.3696 inches.
method. (1.) In Enhanced X-Windows, the functions or procedures that a widget itself implements. (2.) In ODM, executable code associated with an object and defined as the value of a method descriptor for the object. The method can be a command, program, or shell script. See also method descriptor. (3.) An object-oriented programming term synonymous with member function. (4.) In SOM, a combination of a procedure and a name, such that many different procedures can be associated with the same name. In object-oriented programming, invoking a method on an object causes the object to execute a specific method procedure. The process of determining which method procedure to execute when a method is invoked on an object is called method resolution. (The CORBA standard uses the term "operation" for method invocation). SOM supports two different kinds of methods: static methods and dynamic methods. See also static method and dynamic method.
method descriptor. In ODM, a named variable of type method used to define a method or operation to associate with an object. The method can be any executable code such as a command, program, or shell script. See also method and descriptor.
method ID. In SOM, a number representing a zero-terminated string by which SOM uniquely represents a method name. See also somId.
method procedure. In SOM, a function or procedure, written in an arbitrary programming language, that implements a method of a class. A method procedure is defined by the class implementor within the implementation template file generated by the SOM Compiler.
method prototype. In SOM, a method declaration that includes the types of the arguments. Based on method definitions in an IDL source file, the SOM Compiler generates method prototypes in the implementation template. A class implementor uses the method prototype as a basis for writing the corresponding method procedure code. The method prototype also shows all arguments and their types that are required to invoke the method from a client program.
method resolution. In SOM, the process of selecting a particular method procedure, given a method name and an object instance. The process results in selecting the particular function/procedure that implements the abstract method in a way appropriate for the designated object. SOM supports a variety of method-resolution mechanisms, including offset method resolution, name-lookup resolution, and dispatch-function resolution.
method table. In SOM, a table of pointers to the method procedures that implement the methods that an object supports. See also method token.
method token. In SOM, a value that identifies a specific method introduced by a class. A method token is used during method resolution to locate the method procedurethat implements the identified method. The two basic method-resolution procedures are somResolve (which takes as arguments an object and a method token, and returns a pointer to a procedure that implements the identified method on the given object) and somClassResolve (which takes as arguments a class and a method token, and returns a pointer to a procedure that implements the identified method on an instance of the given class). See also method table.
MHz. See megahertz.
MIB Variable. A managed object that is defined in the Management Information Base (MIB). The managed object is defined by a textual name and a corresponding object identifier, a syntax, an access mode, a status, and a description of the semantics of the managed object. The MIB Variable contains pertinent management information that is accessible as defined by the access mode.
Micro Channel architecture. The I/O channel used on the POWERstation and POWERserver system units.
microdocument. A document within a frame that has its own properties and shares components with the main document.
migration installation. An installation method for upgrading to the current release while preserving the existing root volume group. This method preserves the /usr, /tmp, /var, and / (root) file systems, as well as the root volume group, logical volumes, and system configuration files. See also root volume group and logical volume.
mil. A measurement of thickness: 1/1000 inch.
millisecond. A measurement of time: 1/1000 of a second.
minimally consistent. Said of an object that satisfies various conditions set forth in the definition of its class.
minor device number. A number that specifies various types of information about a particular device. For example, a number that distinguishes between several printers of same type. See also major device number.
mirroring. The creation of a mirror image of a primitive.
mixed string. A string consisting of a mixture of DBCS characters and single-byte characters.
mm. (1.) A package of macros for manuscript preparation that supports the eqn and troff commands or the neqn and nroff commands and features annotation, footnoting, indexing, and tables by supporting the tbl command. (2.) Millimeter.
mnemonic. (1.) A symbol chosen to help the user remember the significance of the symbol. (2.) The field of an assembler instruction that contains the acronym or abbreviation for a machine instruction. (3.) In CDE, a single, underlined character in a command. The mnemonic indicates that you can choose the command by typing that letter. Mnemonics are used most commonly in menu commands; however, other buttons may also have mnemonics.
mnemonic overstrike. A nonstandard character created by printing one character on top of another to represent a nonprinting character.
modal. The state in which a secondary window receives keyboard or pointer input that it does not pass on to its associated window.
modal dialog. In AIXwindows, a Dialog widget that interrupts the work session to solicit input from the user.
modal interaction. The communication between separate modes or functions.
modal pop-up. In Enhanced X-Windows, a window that normally is not visible to the window manager and available only after the manager is turned off. This pop-up disables user-event processing except for events that occur in the dialog box.
mode. (1.) A method of operation. (2.) In SNA data communications, the set of rules and protocols to be used for a session. (3.) In the M-Video Capture Adapter, a method of operation such as live or overlay capture. (4.) For Ada programming, see parameter.
model number. In Ada language, an exactly representable value of a real type. Operations of a real type are defined in terms of operations on the model numbers of the type. The properties of the model numbers and of their operations are the minimal properties preserved by all implementations of the real type.
modeless dialog. In AIXwindows, a Dialog widget that solicits input from the user but does not interrupt the work session.
modeless pop-up. In Enhanced X-Windows, a window that is normally visible and is controlled by the window manager.
modeling coordinates, modeling space. In GL, the coordinate system in which all drawing primitives do their drawing. The user can select the position and orientation of the modeling space with regard to the world space by means of translations, rotations, scales, or generalized transformations. The relation between modeling coordinates and world coordinates is determined by the modeling matrix. Modeling coordinates are a useful conceptual device when drawing complex or repetitive scenes. For instance, a paper clip can be defined once in modeling coordinates, and then drawn hundreds of times by moving the modeling coordinates around in world space. See also eye coordinates, screen coordinates, world coordinates, and transformation.
modem (modulator-demodulator). A device that converts digital data from a computer to an analog signal that can be transmitted on a telecommunication line, and converts the analog signal received to digital data for the computer.
modem eliminator. A device that connects a workstation directly to a computer port through a wired connector with a specific pin arrangement. When two devices both function as DTEs (data terminal equipment), the cable that connects them must transmit send and receive signals using a modem eliminator. Synonymous with null modem.
mode name. (1.) The name of an entry in the login mode table. (2.) In SNA, identifies the set of rules and protocols to be used for the session.
mode word. An i-node field that describes the type and state of the i-node.
modification number. The modification level of a program, which is an indicator of changes that do not affect the external interface of the program. The version, release, modification, and fix levels together comprise the program level, fix number, release number, and version number.
modifier. (1.) Word or quantifier used to change an instruction causing the execution of an instruction different from the original one. Consequently, the same instruction, successively changed by a modifier, can be used repetitively to carry out a different operation each time it is used. (2.) In SOM, any of a set of statements that control how a class, an attribute, or a method will be implemented. Modifiers can be defined in the implementation statement of a SOM IDL source file. The implementation statement is a SOM-unique extension of the CORBA specification. [User-defined modifiers can also be specified for use by user-written emitters or to store information in the Interface Repository, which can then be accessed via methods provided by theInterface Repository Framework.]
modifier key. In CDE, a key that when pressed and held along with another key or mouse button changes the meaning of the second key or mouse click. Control, Alt, and Shift are examples.
modifier keys. In Enhanced X-Windows, keys such as Shift, Shift Lock, Control, Alt, Caps Lock, and Meta.
modulation. Changing the frequency or size of one signal by using the frequency or size of another signal.
modulator-demodulator. See modem.
module. (1.) A discrete programming unit that usually performs a specific task or set of tasks. Modules are subroutines and calling programs that are assembled separately, then linked to make a complete program. (2.) In programming languages, a language construct that consists of procedures or data declarations and that interact with other such constructs. (3.) A packaged functional hardware unit designed for use with other components. (4.) Synonym for program unit. (5.) See also run file. (6.) Software that performs functions on messages as they flow between stream head and driver. A module is the STREAMS counterpart to the commands in a shell pipeline except that a module contains a pair of functions that allow independent bidirectional (downstream and upstream) data flow and processing. (7.) In SOM, the organizational structure required within an IDL source filethat contains interface declarations for two (or more) classes that are not a class-metaclass pair. Such interfaces must be grouped within a module declaration. See also object module.
MOM. See monitor mode.
mond. See monitor scheduling daemon.
monitor. (1.) A device that observes and verifies operations of a data processing system. (2.) A functional unit that observes and records selected activities for analysis within a data processing system. Possible uses are to show significant departures from the norm or to determine levels of utilization or particular functional units. (3.) Synonym for display.
monitor mode (MOM). A mode in which an application program can directly access the display adapter.
monitor scheduling daemon. A process that runs on an application server and provides clients with links to processing agents as needed
monochrome. A special case of static gray in which there are only two color map entries. Some monochrome adapters can display shades of gray in the Gray Scale Adapter.
monochrome display. A display device that has only one color. See also gray scale.
more-data bit. See M-bit.
mount. To make a file system accessible.
mouse. A hand-held locator that a user operates by moving it on a flat surface. It allows the user to select objects and scroll the display screen by pressing buttons.
mouse button 1. On a mouse, the leftmost button when configured for right-handed use; the rightmost button when configured for left-handed use. Mouse button 1 is primarily used for selection, and is the default button for the "click" instruction.
mouse button 2. On a three-button mouse, the middle button. On a two-button mouse, the right button if configured for right-handed use or the left button if configured for left-handed use. Mouse button 2 has two modes: Transfer and Adjust.
mouse button 3. On a mouse, the rightmost button when configured for right-handed use; the leftmost button when configured for left-handed use. Mouse button 3 activates pop-up menus.
mouse pointer. A symbol on the screen (such as an arrow or hand) that follows the movement of the mouse as the user moves it.
mouse scaling. The distance the cursor moves relative to the mouse movement. The scaling factor is either 1:1 or 2:1.
mouse threshold. An operating system parameter that determines the amount of horizontal or vertical mouse movements required to move the cursor on the screen.
ms. A package of macros for manuscript and thesis preparation that features automatic footnote numbering and bibliography capabilities.
msb. Most significant bit.
MSB. Most significant byte.
MS-DOS. Microsoft Disk Operating System.
msqid. See message queue ID.
MTU. See maximum transfer unit.
multibyte control. One of the two types of controls valid in a character stream data. Synonym for escape sequence.
multicast address. A multicast address, for FDDI, is an address with the high order bit in the high-order byte of the address set. This type of address allows a user to have multiple stations on a ring set to the same address. If a packet is sent to a multicast address, all stations with that address receive the packet. A multicast address is sometimes referred to as a group address.
multidrop. (1.) Stations connected to a multipoint channel at one location. (2.) A network configuration in which there are one or more intermediate nodes on the path between a central node and an endpoint node.
multihomed machine. A machine that has more than one configured network adapter and more than one host name.
multihomed server. A server that has more than one network interface running.
multiline. More than one communications line.
multimode optical fiber. A graded-index or step-index optical fiber that allows more than one bound mode to propagate. Contrast with single-mode optical fiber.
multiple inheritance. An object-oriented programming technique implemented in C++ through derivation, in which the derived class inherits members from more than one base class.
multiplex. To interleave or simultaneously transmit two or more messages on a single channel.
multiplexed device. (1.) A device that takes several input signals and combines them into a single output signal so that each of the input signals can be recovered. (2.) A device capable of interleaving events of two or more activities or capable of distributing events of an interleaved sequence to the respective activities.
multiplexer. See multiplexed device.
multipoint. Pertaining to communication among more than two stations over a single telecommunications line.
multipoint link. A circuit that interconnects several stations.
multitasking. A mode of operation that provides for concurrent performance or interleaved processing of two or more tasks. Synonym for tasking.
multiuser mode. A mode of operation that enables two or more users to use the services of a processor within a given period of time. The usage is usually serial unless otherwise specified.
mutex. Jargon for mutual exclusion lock. Use of this type of lock excludes all threads other than the lock holder from any access whatsoever to the locked resource.
mutual exclusion mechanism. A means for preventing two separately executing pieces of code from interfering with each other's use of a particular data object. For example, if one thread is executing a function that modifies a shared data structure, then the application may need to prevent other threads from attempting to read the data simultaneously, before the modifications are complete.
MVS. Multiple Virtual Storage.
MVS/TSO. A type of operating system used on a System/370 computer.
mwm. AIXwindows window manager. See also window manager.