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IAR. See instruction address register.

IC. See ICU.

ICCC. Inter-Client Communications Conventions. A standard abbreviation for the manual that contains a detailed set of guidelines for client applications using the Enhanced X-Windows system and the AIXwindows toolkit. See also ICCCM.

ICCCM. Inter-Client Communications Conventions manual. See also ICCC.

ICMP. See Internet Control Message Protocol.

icon. (1.) A picture or graphical representation of an object on a display screen to which a user can point to with a device such as a mouse in order to select a particular operation or perform a certain action. (2.) In Common Desktop Environment, the visual representation of a file or directory, or an object used by the desktop, consisting of a picture on the desktop or in a directory window.

icon box. In AIXwindows, a window used as a visual storage area for icons representing minimized windows.

Icon Editor. In CDE, the software application used to create new icons and to modify existing icons.

icon layout policy. In AIXwindows, a specification that determines whether icons representing minimized windows are placed on the root window or within an icon box.

iconify. See icon.

ICU (IC). Instruction cache unit.

ID. Identification. See identifier.

idempotent. A class of operations. An operation is idempotent if its results do not affect the results of any operation. For example, a call that returns the time is idempotent.

identifier (ID). (1.) A name that refers to a data object. An identifier contains some combination of letters, digits, and underscores, but its first character cannot be a digit. (2.) In programming languages, a lexical unit that names a language object, such as the name of an array, record, label, or procedure. An identifier usually begins with a letter optionally followed by letters, digits, or other characters. (3.) A sequence of bits or characters that identifies a program, device, or system to another program, device, or system. (4.) In Enhanced X-Windows, a unique value associated with a resource that a client program uses to name the resource. An identifier can be used over any connection to name the resource.

IDL source file. In SOM, a user-written .idl file, expressed using the syntax of the Interface Definition Language (IDL), which describes the interface for a particular class (or classes, for a module). The IDL source file is processed by the SOM Compiler to generate the binding files specific to the programming languages of the class implementor and the client application. (This file may also be called the "IDL file," the "source file," or the "interface definition file.")

idle list. A list of secondary stations on a network that are polled less often by the primary station due to their inactivity.

idle time. The part of operable time during which a functional unit is not operated.

IDP. Internet Datagram Protocol. A simple, unreliable datagram protocol, which is used to support the SOCK_DGRAM abstraction for the Internet Protocol family.

IEEE. Institute of Electrical and Electronics Engineers.

IEEE 754. Binary Floating Point Standard.

IEEE 802.3. Ethernet LAN specification.

IEEE 802.5. Token-Ring LAN specification.

IETF. Internet Engineering Task Force.

IF expression. An expression in a procedure that tests for a condition. The action performed by the procedure depends on the result of the test.

if statement. (1.) A C language conditional statement that contains the keyword if followed by an expression in parentheses (the condition), a statement (the action), and an optional elseclause (the alternative action). (2.) A conditional statement that specifies a condition to be tested and the action to be taken if the condition is satisfied.

I-field. Information field.

I-field bytes. Data within the information field of a transmit or receive sequenced data frame.

ignore. In DOS, the option to disregard the device error and continue processing.

i-list. In a Base Operating System file system, blocks 2 through n compose the i-list, which contains structures (i-nodes) that relate a file to the data blocks or disk. The size of the i-list depends on the size of the mounted file system. See also i-node and superblock.

illegal. A violation of an architecture rule that an implementation is required to report. See also unpredictable.

image cache. In AIXwindows, a means of associating an image with a name. Once this association is in place, the appropriate AIXwindows subroutines can generate pixmaps through references to an .Xdefaults file (by name) and through an argument list (by pixmap). See also pixmap.

image structure. The existing image in an XmInstallImage function.

immediate data. (1.) In Assembler language, actual data appearing in an instruction, as opposed to the symbolic name of some data. The data is immediately available from the instruction and therefore does not have to be read from memory. (2.) Data transferred during instruction run time.

immediate mode. In GL, in this mode, graphics commands are executed immediately rather than being compiled into a display list.

immediate subclass. A subclass, of a class C, having no super classes that are themselves subclasses of C.

immediate subobject. One object that is a value of an attribute of another.

immediate superclass. The superclass, of a class C, having no subclasses that are themselves superclasses of C.

immediate superobject. One object that contains another among its attribute values.

IMPL. Initial microprogram load.

implementation (Or object implementation). In SOM, the specification of what instance variablesimplement an object's state and what proceduresimplement its methods (or behaviors). In DSOM, a remote object's implementation is also characterized by its server implementation(a program).

Implementation Repository. In SOM, a database used by DSOM to store the implementation definitions of DSOM servers.

implementation statement. An optional declaration within the body of the interface definition of a classin a SOM IDL source file, specifying information about how the class will be implemented (such as, version numbers for the class, overriding of inherited methods, or type of method resolution to be supported by particular methods). This statement is a SOM-unique statement; thus, it must be preceded by the term "#ifdef __SOMIDL__" and followed by "#endif". See also interface declaration.

implementation template. In SOM, a template file containing stub procedures for methods that a class introduces or overrides. The implementation template is one of the binding files generated by the SOM Compiler when it processes the IDL source file containing class interface declarations. The class implementor then customizes the implementation, by adding language-specific code to the method procedures.

implicit method parameter. In SOM, a method parameter that is not included in the IDL interfacespecification of a method, but which is a parameter of the method's procedure and which is required when the method is invoked from a client program. Implicit parameters include the required Environmentparameter indicating where exception information can be returned, as well as a Context parameter, if needed.

implicit type conversion. A type conversion generated by the compiler as the result of an association between variables of different types. For example, initializing a floating-point array to the value of a loop counter is an implicit type conversion from integer to floating-point.

implied DO. In FORTRAN, an indexing specification with a list of data elements, rather than a set of statements, as its range. Similar to an FORTRAN DO statement, however, without using the word DO.

import. (1.) In NCS, to request the operations defined by an interface. A client imports an interface from a server. (2.) To bring data in from another system. Contrast with export.

imports. In Ada language, all compilation units named in the context specification of a library unit (stated in its with clauses) and any supporting unit specifications introduced by the compiler, for example, the standard package SYSTEM. The imports of a secondary unit are all the units named in its context specification, any supporting unit requirements introduced by the compiler; its associated parent unit (if any), and the bodies of any generic specifications included among its other imports.

in. See inch.

inaccessible. In XOM, said of an object for which the client does not possess a valid designator or handle.

inactive. Describes a window that does not have the input focus.

Inbox. In CDE, the main or default Mailer container. The Inbox receives all incoming mail. Messages can be moved out of the Inbox and put in various containers.

inch (in). 2.54 centimeters or 25.4 millimeters.

include file. A text file that contains declarations used by a group of functions, programs, or users. Synonymous with header file. See also include statement.

include statement. A computer language preprocessor statement that directs the processor to retrieve a specific file that contains instructions and data the program may need. See also include file.

incoming call. In X.25 communications, a call arriving at the data terminal equipment (DTE).

incoming-call packet. In X.25 communications, a call supervision packet transmitted by a DCE to inform a DTE of a call requested by another DTE. See also packet.

incomplete class declaration. A C++ class declaration that does not define any members of a class. Until a class is fully declared, or defined, you can only use the class name where the size of the class is not required. Typically, an incomplete class declaration is used as a forward declaration.

incremental backup. The process of copying files that have been opened for reasons other than read-only access since the last backup was created and that meet the backup frequency criteria. Contrast with full backup.

incremental update. In SOM, a revision to an implementation template file that results from reprocessing of the IDL source file by the SOM Compiler. The updated implementation file will contain new stub procedures, added comments, and revised method prototypes reflecting changes made to the methoddefinitions in the IDL specification. Importantly, these updates do not disturb existing code that the class implementor has defined for the prior method procedures.

index. (1.) A table containing the key value and location of each record in an indexed file. (2.) A computer storage position or register whose contents identify a particular element in a set of elements. (3.) A list of the contents of a file or a document, together with keys or references for locating the contents. See also base register.

index constraint. In Ada language, an index constraint for an array type specifies the lower and upper bounds for each index range of the array type.

index priority. Priority of an attribute type in search queries.

indexed application widget. Any widget named in the User Interface Language (UIL) that is not the child of any other widget in the User Interface Definition (UID) hierarchy.

indexed component. In Ada language, an indexed component denotes a component in an array. It is a form of name containing expressions which specify the values of the indices of the array component. An indexed component may also denote an entry in a family of entries.

indexed fields. An area in a structured data file that contains tree data paths.

indexed instruction. An instruction that uses an indexed address.

indicator. (1.) An internal switch that communicates a condition between parts of a program or procedure. (2.) A device that can be set to a prescribed state, usually according to the result of a previous process or on the occurrence of a specified condition in the equipment. The device usually indicates the existence of the state and may be used to determine the selection among alternative processes.

indirect block. A block containing pointers to other blocks.

industry-standard benchmark. A benchmark that has been adopted by consensus or by some (presumably neutral) sponsoring organization as constituting a meaningful measure of some aspect of computer-system performance. There are many counter-examples to the assumption that an improvement in industry-standard benchmark performance corresponds to an improvement in the performance experienced by users.

inferiors. In Enhanced X-Windows, all the subwindows nested below a window.

infinity. (1.) A name for the upper boundary of the set of numbers. (2.) In binary floating-point concepts, a value with an associated sign that is mathematically greater in magnitude than any binary floating point number.

information field overflow (I-field overflow). Condition that occurs when the size of the information field in the receive data exceeds the primary station's buffer capacity. Some of the information field is lost.

informational message. (1.) A message that provides information to the operator but does not require a response. (2.) A message that is not the result of an error condition.

inherit. To copy resources or attributes from a parent to a child.

inheritance. (1.) In AIXwindows and Enhanced X-Windows, the passing of class resources from an object superclass downstream in the class hierarchy to an object subclass. (2.) An object-oriented programming technique that allows you to use existing classes as bases for creating other classes. (3.) In SOM, the technique of defining one class (called a subclass, derived class, or child class) as incremental differences from another class (called the parent class, base class, superclass, or ancestor class). From its parents, the subclass inherits variables and methods for its instances. The subclass can also provide additional instance variables and methods. Furthermore, the subclass can provide new procedures for implementing inherited methods. The subclass is then said to override the parent class's methods. An overriding method procedure can elect to call the parent class's method procedure. Such a call is known as a parent method call. See also subclassing.

inheritance hierarchy. In SOM, the sequential relationship from a root class to a subclass, through which the subclass inherits instance methods, attributes, and instance variables from all of its ancestors, either directly or indirectly. The root class of all SOM classes is SOMobject.

initial program load (IPL). (1.) The initialization procedure that causes an operating system to commence operation. Synonymous with system restart and system startup. (2.) The process by which a configuration image is loaded into storage at the beginning or a work day or after a system malfunction. (3.) The process of loading system programs and preparing a system to run jobs.

initial program load device (IPL device). The input/output device, usually a fixed disk or diskette, from which the system software is loaded when the machine is turned on.

initial sequence controller. One of three control programs for the initial program load (IPL) ROM. The initial sequence controller accepts control after the hardware initialization and passes control to the core sequence controller.

initialize. (1.) In programming languages, to set the starting value of a data object. (2.) To set counters, switches, addresses, or contents of storage to zero or other starting values at the beginning of, or at prescribed points in, the operation of a computer routine. (3.) To prepare for use, such as initializing a diskette. (4.) To prepare the system for operation. After loading the kernel into memory, the system runs internal checks, initializes all memory and some devices, and analyzes the root file system.

initializer. The assignment operator followed by an expression or multiple expressions for aggregate variables.

inline. See inline component.

inline component. A component within a component that has its own properties and can contain anything a component contains. It is created from the same set of masters as a component.

inline expansion. An optimization in which the reference to a procedure is replaced with the code of the procedure itself, to eliminate calling overhead.

inline function. In C++, inlining is a hint to the compiler to perform inline expansion of the body of a function member. Functions declared and defined simultaneously in a class definition are inline. You can also explicitly declare a function inline by using the keyword inline. Both member and nonmember functions can be inlined.

inlining. See inline expansion.

i-node. The internal structure that describes the individual files in the operating system; there is one i-node for each file. An i-node contains the node, type, owner, and location of a file. A table of i-nodes is stored near the beginning of a file system. Synonym for file index. See also i-list and i-node number.

i-node number. A number specifying a particular i-node file in the file system. See also i-node.

inodetab. A kernel parameter that establishes a table in memory for storing copies of i-nodes for all active files.

input. (1.) Data to be processed. (2.) In Pascal, a predefined standard file definition.

input data type. The type of data contained in the input file. Examples are ASCII and PostScript.

input device. (1.) A physical device that provides data to a computer. (2.) The device that is the source of the software you are installing. The input device can be a tape drive, CD-ROM drive, diskette drive, or a directory.

input field. (1.) An area in a display file into which you can type data. (2.) In computer graphics, an unprotected field on a display surface in which data can be entered, modified, or erased.

input file. A file opened in order to allow records to be read.

input focus. In a graphics environment, a window defining the scope for processing keyboard input. By default, keyboard events are sent to the client using the window the pointer is in. It is also possible to attach the keyboard input to a specific window. Events are then sent to the appropriate client regardless of the pointer position. Synonymous with focus window. See also inactive.

input list. A list of variables to which values are assigned from input data.

input manager. In a graphics environment, a client that controls keyboard input and is usually part of a window manager.

input mode. An open mode in which records can be read from the file.

Input Only window. In a graphics environment, an invisible window that can be used to control such things as cursors, input event generation, and grabbing. This window cannot be used for graphics requests.

input redirection. The specification of an input source other than the standard one.

input semantics. The specified order and format in which user input must be entered.

input stream. The sequence of operation control statements and data given to the system from an input device.

input/output (I/O). (1.) Pertaining to either input, output, or both between a computer and a device. (2.) Pertaining to a device whose parts can perform an input process and an output process at the same time. (3.) Pertaining to a functional unit or channel involved in an input process, an output process, or both, concurrently or not, and to the data involved in such a process.

input/output channel (IO channel). (1.) In a data processing system, a functional unit that handles transfer of data between internal and peripheral equipment. (2.) In a computing system, a functional unit, controlled by a processor, that handles transfer of data between processor storage and local peripheral devices.

input/output channel controller (IOCC). A hardware component that supervises communication between the input/output bus and the processor.

input/output configuration data set (IOCDS). A configuration definition built by the I/O configuration program (IOCP) and stored on disk files associated with the processor controller.

input/output configuration program (IOCP). The program that defines the I/O configuration data required by the processor complex to control I/O requests.

input/output device number. A value assigned to a device driver by the guest operating system or to the virtual device by the virtual resource manager. This number uniquely identifies the device regardless of whether it is real or virtual.

input/output file. A file opened for input and output use.

input/output subsystem. That part of the operating system comprised of processes and device managers that provides the mechanisms for data transfer and I/O device management and control.

InputOutput window. In a graphics environment, a kind of opaque window used for input and output. InputOutput windows can have both InputOutput and InputOnly windows as inferiors.

inquiry. (1.) A request for information in storage. (2.) A request that puts a display station into inquiry mode. (3.) In data communications, a request for information from another system.

insert cursor. The position of the cursor marking where new characters will be added when entering text.

insert mode. (1.) A keyboard operation that puts new text within existing text at the cursor position. (2.) The source entry utility operation during which source statements are typed in and added as new records in a source member. (3.) In the Token-Ring Network, to make an attaching device an active part of a ring.

insertion cursor position. The point at which text will be inserted.

insertion point. In Common Desktop Environment, the point at which text is inserted when you type. It usually appears as a flashing vertical line or underline.

install. (1.) To add a program, program option, or software program to the system in a manner such that it is runnable and interacts properly with all affected programs in the system. (2.) To connect a piece of hardware to the processor. (3.) The process of connecting used when discussing the process of connecting something to the internal portion of the processor.

Install Icon. In CDE, an item on a subpanel used to install icons into the Front Panel using drag and drop.

installation. (1.) The procedure of adding a program or program option to the mass storage medium of the computer, making the program runnable, and ensuring that the program interacts properly with all other affected programs in the system. (2.) The task of adding a device driver to the system and activating the driver so that it can be used. (3.) The task of connecting a piece of hardware to the processor or of adding a software program to the system.

Installation Assistant. An application used to perform system configuration tasks.

installation image. An installation image contains a copy of the software you are installing in backup format, as well as copies of other files the system needs to install the software product.

installation script. A shell script or executable file created by the developer of an application program to install the program. The script file must follow specific guidelines in order to be compatible with the program installation tools that are provided in the operating system.

instance. (1.) A concrete realization of an abstract object class. An instance of a widget or gadget is a specific data structure that contains detailed appearance and behavioral information that is used to generate a specific graphical object on-screen at runtime. See also widget instance and instance record. For Ada programming, see generic unit. (2.) An object-oriented programming term synonymous with "object". An instance is a particular instantiation of a data type. It is simply a region of storage that contains a value or group of values. For example, if a class box is previously defined, two instances of a class box could be instantiated with the declaration: box box1, box2; (3.) In XOM, an object in the category represented by a class.

instance method. In SOM, a method valid for an object instance (as opposed to a class method, which is valid for a class object). An instance method that an object responds to is defined by its class or inherited from an ancestor class.

instance record. A particular widget record that contains the data objects pertaining to the identity of any given widget as an instance. See also record, widget record, and instance.

instance token. In SOM, a data tokenthat identifies the first instance variable among those introduced by a given class. The somGetInstanceToken method invoked on a class object returns that class's instance token. See also data token.

instance variables. (Or, instance data.) In SOM, variables declared for use within the method proceduresof a class. An instance variable is declared within the body of the implementation statement in a SOM IDL source file. An instance variable is "private" to the class and should not be accessed by a client program. Contrast with attribute.

instant duration locks. Locks that behave as if they were obtained and then immediately released. These are commonly used when a large number of data objects require locking, but the transaction wishes to avoid obtaining some of the necessary locks while waiting an unknown amount of time for another transaction to release the other required locks. These are primarily useful for implementing schemes such as Jim Gray's key-range locking (see also his Transaction Processing: Concepts and Techniques).

instantiate. (1.) To make an instance of; to replicate. (2.) In object-oriented programming, to represent a class abstraction with a concrete instance of the class. (3.) In AIXwindows, to create a specific concrete instance of that general class. (4.) To create or generate a particular instance (or object) of a data type. For example, an instance box1 of class box could be instantiated with the declaration: box box1;

instruction. A program statement that specifies an operation to be performed by the computer, along with the values or locations of operands. This statement represents the programmer's request to the processor to perform a specific operation.

instruction address register (IAR). A system control register containing the address of the next instruction to be run. The IAR can be accessed by way of a supervisor call in supervisor state, but cannot be directly addressed in problem state. Synonymous with program counter. See also location counter.

instruction cache. A cache for providing program instructions to the processor faster than they can be obtained from RAM.

instruction pointer (IP). See instruction address register.

instruction scheduling. A compiler optimization that schedules instructions to the different processing units of the CPU so that maximum instruction overlap can occur.

int specifier. In C language, one of the words int, short, short int, long, long int, unsigned, unsigned int, unsigned short, unsigned short int, unsigned long, or unsigned long int,which describe the type of data a variable represents.

integer. A positive or negative whole number or zero.

integer constant. (1.) A decimal constant containing no decimal point. (2.) An octal or hexadecimal constant. (3.) A string of decimal digits containing no decimal point.

integer expression. An arithmetic expression with only integer type values.

integer type. An arithmetic data type that consists of integer values. In Ada language, an integer type is a discrete type whose values represent all integer numbers within a specific range.

integral object. In the C language, a character object, an object having an enumeration type, or an object having the type short, int, long, unsigned short, unsigned int, or unsigned long.

integrity. A protection level that may be specified in secure RPC communications that ensures that data transferred between two principals has not been modified in transit.

intention locks. Locks used for hierarchical resources that permit an application to avoid locking a large data object, such as a file of records, when it only needs to modify a portion of the data object, such as one record in a file. Obtaining the intention lock on the file indicates that some records in the file may be changing currently, but allows access to records that are not further locked against access.

interaction. A continuing cycle of reciprocal action between a user and one or more software applications through input devices (a keyboard, mouse, file server, and so on) and output devices (a display, printer, file server, and so on).

interactive. Pertaining to an activity that involves requests and replies, such as between a system user and a program or between two programs.

interactive processing. A processing method in which each system user action causes response from the program or the system. Contrast with batch processing.

interface. (1.) A common boundary, but not of internal connections. An interface can be a hardware component to link two devices or a portion of storage or registers accessed by two or more computer programs. Synonymous with command interpreter. (2.) A shared boundary between two functional units, defined by functional characteristics, common physical interconnection characteristics, signal characteristics, and other characteristics. (3.) Hardware or software, or both, that link systems, programs, or devices. (4.) Synonymous with shell. (5.) A set of operations. The Network Computing Architecture specifies a Network Interface Definition Language for defining interfaces. (6.) In SOM, the information that a client must know to use a class--namely, the names of its attributes and the signatures of its methods. The interface is described in a formal language (the Interface Definition Language, IDL) that is independent of the programming language used to implement the class's methods. See also extended interface and limited interface.

interface declaration. (Or interface statement.) In SOM, the statement in the IDL source file that specifies the name of a new class and the names of its parent class(es). The "body" of the interface declaration defines the signatureof each new method and any attribute(s) associated with the class. In SOM IDL, the body may also include an implementation statement(where instance variables are declared or a modifier is specified, for example to override a method). See also implementation statement.

Interface Definition Language (IDL). In SOM, the formal language (independent of any programming language) by which the interface for a class of objects is defined in a .idl file, which the SOM Compiler then interprets to create an implementation template file and binding files. SOM's Interface Definition Language is fully compliant with standards established by the Object Management Group's Common Object Request Broker Architecture (CORBA).

interface, extended. See extended interface.

interface icon. Any pictorial representation of a selection choice appearing within an interface.

interface, limited. See limited interface.

Interface Repository (IR). The database that SOM optionally creates to provide persistent storage of objects representing the major elements of interface definitions. Creation and maintenance of the IR is based on information supplied in the IDL source file. The SOM IR Framework supports all interfaces described in the CORBAstandard.

Interface Repository Framework. In SOM, a set of classes that provide methods whereby executing programs can access the persistent objects of the Interface Repository to discover everything known about the programming interfaces of SOM classes.

interior gateway. A gateway that communicates only with gateways on its own autonomous system.

interlacing. A method of doubling vertical resolution by displacing odd video frames by one-half scan line.

interlanguage call. In a program written in a given language, any reference to a procedure written in a different language.

intermediate data type. Any of the basic data types in terms of which the other, substantive data types of the interface are defined.

intermediate nodes. On the widget tree, widgets with one or more children. See also widget tree.

intern. The procedure of defining an atom.

internal clocking. In data communications, data clocking provided by an adapter.

internal data definition. A description of a variable appearing at the beginning of a block that directs the system to allocate storage for that variable and makes that variable accessible to the current block.

internal data structures. The format of other data stored internally by a program or function. Used to perform type conversion on argument lists.

internal routine. A routine available only within the lexical scope in which it was declared.

international character support. Synonym for national language support.

International Standards Organization (ISO). An international body that standardizes goods and services. For Enhanced X-Windows, standards relating to character sets and fonts.

Internet. (1.) A wide area network connecting thousands of disparate networks in industry, education, government, and research. The Internet network uses TCP/IP as the standard for transmitting information. (2.) Any wide area network connecting more than one network.

Internet address. The numbering system used in TCP/IP Internetwork communications to specify a particular network or a particular host on that network with which to communicate. Internet addresses are commonly denoted in dotted decimal form.

Internet Control Message Protocol (ICMP). A protocol used by a gateway to communicate with a source host, for example, to report an error in datagram. It is an integral part of Internet Protocol (IP).

Internet Protocol (IP). The protocol that provides the interface from the higher level host-to-host protocols to the local network protocols. Addressing at this level is usually from host to host.

Internet Router. Enables an IP host to act as a gateway for routing data between separate networks that use a specific adapter.

internetwork. Any wide area network connecting more than one network.

interoperability. Ability of a system or a product to work with other systems or products without special effort on the part of the customer. Becomes a quality of increasing importance for information technology products as the concept that "the network is the computer" becomes a reality.

interpreted routine. A routine that decodes instructions written as pseudocodes and immediately executes those instructions. See also compile.

interpreter. A tool that allows a program to be run immediately, without recompiling or relinking.

interprocedural analysis. The process of inspecting referenced procedures for information on relationships between arguments, returned values, and global data.

inter-process communication (IPC). (1.) Used for programs to communicate data to each other and to synchronize their activities. Semaphores, signals, and internal message queues are common methods of inter-process communication. (2.) In Enhanced X-Windows, a communication path. See also client.

interrupt. (1.) In data communications, to take an action at a receiving station that causes the sending station to end a transmission. (2.) To stop a process temporarily. (3.) A signal sent by an I/O device to the processor when an error has occurred or when assistance is needed to complete I/O. An interrupt usually suspends the running of the program that is currently running. Contrast with exception and signal.

interrupt-confirmation packet. In X.25 communications, a packet used to acknowledge the receipt of an interrupt packet. See also packet.

interrupt packet. In X.25 communications, an expedited packet that is allowed to overtake normal data packets (which are delivered in sequence). See also packet.

intrinsic function. In FORTRAN, a function that is supplied with the run-time environment that performs math, character, logical, or bit-manipulation operations.

intrinsics. In Enhanced X-Windows, a set of management mechanisms that provides for constructing and interfacing between composite widgets, their children, and other clients. Also, intrinsics provide the ability to organize a collection of widgets into an application.

inverse. A matrix that results from a mathematical operation on a matrix such that the two matrices can be multiplied together to obtain the unit matrix.

inverse transpose. The inverse of a matrix after it has been transposed.

inverted index. An index into a bibliography database that allows for direct access. This can be compared to the thumb cuts of a dictionary, which allow a user to move to the exact location of the word being searched.

invocation stack. A list of programs linked together as a result of programs calling other programs within the same job. Synonymous with program stack.

invoke. To start a command, procedure, or program.

invoke ID. An integer used to distinguish one (directory) operation from all other outstanding ones.

IO. See IOU.

I/O. See input/output.

I/O channel. See input/output channel.

I/O configuration. The collection of channel paths, control units, and I/O devices that attaches to the processor unit.

I/O error. An error in the processing of input or output device data.

I/O Stream Library. A C++ class library that provides the facilities to deal with many varieties of input and output.

IOCC. See input/output channel controller.

IOCDS. I/O configuration data set.

IOT fault. A signal (SIGIOT) that abnormally ends a process.

IOU (IO). Input/output unit.

IP. See Internet Protocol.

IP address. An address in a network using the Internet Protocol. It is a 32-bit integer usually written in dotted decimal notation, where each successive eight bits is translated to an integer and separated from the other components using a dot.

IP socket. The port concatenated with the Internet Protocol (IP) address.

IPC. See inter-process communication.

IPL. See initial program load.

IPL device. initial program load device.

ips. Inches per second, a measure of tape drive speed and performance.

ISC. See initial sequence controller.

ISO. See International Standards Organization.

ISO 7776. The ISO description of LAPB-compatible DTE data link procedures.

ISO 8208. See X.25.

isolation level. A field in the specification of an open file descriptor (OFD) that determines the degree to which operations performed with that OFD are isolated from other operations using that OFD. Operation isolation is achieved by the use of locks obtained internally on behalf of each operation. The value of this field determines how locks are obtained and held on behalf of operations performed using that OFD.

ITE. In CDE, Internal Terminal Emulator. ITE allows use of a bitmapped display as a terminal (through command-line mode from the login screen).

item. The data in one line of an indexed field.

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