Easy Install. An application used to install optional software or service updates in the form of software bundles.
EBCDIC. See extended binary-coded decimal interchange code.
EBCDIC character. Any one of the symbols included in the 8-bit EBCDIC set.
EC. Engineering Change level.
ECB. (1.) See event control bit. (2.) Event control block. (3.) Electronic codebook.
ECC. (1.) See error-checking and correction. (2.) Error correction code.
echo. (1.) A reflected signal on a communications channel. On a communications terminal, each signal is displayed twice, once when entered at the local terminal and again when returned over the communications link. This allows the signals to be checked for accuracy. (2.) In computer graphics, the immediate notification of the current values provided by an input device to the operator at the display console. (3.) In word processing, to print or display each character or line as it is typed in.
ECM. Entity coordination management.
ECMA. European Computer Manufacturers' Association.
edit. (1.) To add, change, delete, rearrange, or modify the form or format of data. (2.) To check the accuracy of information and to indicate if an error is found.
edit buffer. A temporary storage area used by an editor.
effective rate. The average sustained speed at which a device operates under real-world conditions, when processing a representative workload.
effective root directory. The point where a system starts when searching for a file. Its path name begins with a / (slash). The chroot subroutine causes the directory named by the path parameter to become the effective root directory.
effective user ID. (1.) The user ID associated with the last authenticated user or the last setuid program. Equal to either the real or the saved user ID. (2.) The current user ID, but not necessarily the user's login ID. For example, a user logged in under a login ID may change to another user's ID. The ID to which the user changes becomes the effective user ID until the user switches back to the original login ID. All discretionary access decisions are based on the effective user ID.
EGA. The Enhanced Graphics Adapter.
EGP. Exterior Gateway Protocol. The mechanism that allows the exterior gateway of an autonomous system to share routing information with exterior gateways on other autonomous systems.
EIA. Electronic Industries Association.
EIA-232D. An EIA interface standard that defines the physical, electronic, and functional characteristics of an interface line that connects a communication device and associated workstation. It uses a 25-pin connector and an unbalanced line voltage.
EIA-422A. An EIA interface standard that defines the physical, electronic, and functional characteristics of an interface line connecting a computer to communications equipment. It uses a balanced line voltage for noise reduction and longer distance capability. The system unit uses the send and receive pins from the set of 40 pins defined by the EIA-422A interface.
elaborated type specifier. Typically used in C++ in an incomplete class declaration or to qualify types that are otherwise hidden.
elaboration. In Ada language, the elaboration of a declaration is the process by which the declaration achieves its effect (such as creating an object); this process occurs during program execution.
electromagnetic compatibility. The design and test of products to meet legal and corporate specifications dealing with the emissions and susceptibility to frequencies in the radio spectrum. Electromagnetic compatibility is the ability of various electronic equipment to operate properly in the intended electromagnetic environment.
electronic mail. Synonym for mail.
element. (1.) The smallest unit of data in a table or array. (2.) In a set, an object, entity, or concept having the properties that define a set. Synonymous with member. (3.) In SNA, the particular resource within a subarea that is identified by an element address. (4.) The component of an array, subrange, enumeration, or set. (5.) In AIXwindows, an object or similar data structure having the properties that define a class.
else clause. The part of an if statement that contains the keyword else followed by a statement. The else clause provides an action that is started when the if condition evaluates to a value of 0 (false).
em. In a specific type size, an em is the same number of points as there are to that specific size. See also en.
embedded blanks. Blanks that are surrounded by any other characters.
EMC. See electromagnetic compatibility.
emitter. In SOM, generically, a program that takes the output from one system and converts the information into a different form. Using the Emitter Framework, selected output from the SOM Compiler (describing each syntactic unit in an IDL source file) is transformed and formatted according to a user-defined template. Example emitter output, besides the implementation template and language bindings, might include reference documentation, class browser descriptions, or "pretty" printouts.
emphasized. A form of double-strike printing in which characters are printed in multiple passes (usually two) with a slight offset, creating an artificial bold type. Emphasized printing is used to fill gaps and rough appearance in dot-matrix character forms. It also prints a bold font without changing the mounted character set. See also boldface and double-strike.
emulation. (1.) The use of programming techniques and special machine features to permit a computing system to run programs written for another system. (2.) Imitation. For example, when one computer imitates the characteristics of another computer.
emulator. A program that causes a computer to act as a workstation attached to another system.
en. In the troff command, an en is half the size, in points, of an em. In the nroff command, an em and an en are identical size. See also em.
enable. (1.) To make functional. (2.) In interactive communications, to load and start a subsystem. Contrast with disable.
encapsulation. (1.) Hiding the internal representation of data objects and implementation details of functions from the client program. This enables the end user to focus on the use of data objects and functions without having to know about their representation or implementation. (2.) In SOM, an object-oriented programming feature whereby the implementation details of a class are hidden from client programs, which are only required to know the interface of a class (the signatures of its methods and the names of its attributes) in order to use the class's methods and attributes.
encoder/decoder. In the SOM Persistence Framework, a class that knows how to read/write the persistent object format of a persistent object. Every persistent object is associated with an Encoder/Decoder, and an encoder/decoder object is created for each attribute and instance variable. An Encoder/Decoder is supplied by the Persistence Framework by default, or an application can define its own.
encrypt. To convert clear data into cipher text.
encryption key. A key generated by the makekey command to use with programs that perform encryption. Its input and output are usually pipes.
end signal. In an online conference, a mutually agreed upon character that indicates the end of a comment by a participant. Common end signals are o and oo.
endian. An attribute of data representation that reflects how certain multi-octet data are stored in memory. See also big endian and little endian.
end-to-end transit delay. In X.25 communications, an optional CCITT-specified facility.
enforced lock. A type of lock that a process holds on a region of a file preventing any other process from accessing that region with read or write system calls. In addition, the create command is prevented from truncating the files. See also advisory lock.
enhanced graphics adapter (EGA). An adapter, such as the Enhanced Graphics Adapter, that provides high-resolution graphics, allowing the use of a color display for text processing as well as graphics applications.
Enhanced X-Windows. A collection of basic functions for developing a variety of application environments. Toolkit functions manage Toolkit initialization, widgets, memory, events, geometry, input focus, selections, resources, translation of events, graphics contexts, pixmaps, and errors. See also AIXwindows Environment.
enqueue. To place items in a queue. Contrast with dequeue.
enter. (1.) To send information to the computer by pressing the Enter key. (2.) To place a message on the line to be transmitted from a terminal to the computer.
Enterprise Systems Connection. See ESCON.
entry. (1.) In FORTRAN, a language construct within a procedure, designating the start of the execution sequences of the procedure. (2.) In Ada language, an entry is used for communication between tasks. Externally, an entry is called just as a subprogram is called; its internal behavior is specified by one or more accept statements specifying the actions to be performed when the entry is called. (3.) An element of information in a table, list, queue, or other organized structure of data or control information. (4.) A single input operation on a workstation.
entry class. In the SOM Emitter Framework, a class that represents some syntactic unit of an interface definition in the IDL source file.
entry point. (1.) An address or label of the first instruction performed upon entering a computer program, routine, or subroutine. A program may have several different entry points, each corresponding to a different function or purpose. (2.) In a routine, any place to which control can be passed.
entry point vector (EPV). A record in which fields are pointers to procedures that implement the operations defined by an interface.
entry sequence number (ESN). The number corresponding to the order in which the record was entered into an entry-sequenced file. The primary index of an entry-sequenced file is based upon the ESNs of its records. See also entry-sequenced file.
entry-sequenced file. A record-oriented file in which the records are stored in the order in which they were entered into the file. The primary index of an entry-sequenced file is based on the entry sequence numbers (ESNs) corresponding to the order of record insertion. Also referred to as sequential file. See also entry sequence number.
enumerated scalar type. A scalar defined by enumerating the elements of the type. Each element is represented by an identifier.
enumeration constant. In C language, an identifier (with an associated integer value) defined in an enumerator. You can use an enumeration constant anywhere an integer constant is allowed.
enumeration data type. A type that represents integers and a set of enumeration constants. Each enumeration constant has an associated integer value.
enumeration tag. The identifier that names an enumeration data type.
enumeration type. In Ada language, a discrete type whose values are represented by enumeration literals which are given explicitly in the type declaration. These enumeration literals are either identifiers or character literals.
enumerator. An enumeration constant and its associated value.
environment. (1.) The settings for shell variables and paths set when the user logs in. These variables can be modified later by the user. (2.) A named collection of logical and physical resources used to support the performance of a function. (3.) In AIX Common Desktop Environment, the set of rule files, resources, and message files that define the appearance and behavior of a specific desktop configuration.
Environment parameter. In SOM, a CORBA-required parameter in all method procedures, it represents a memory location where exception information can be returned by the object of a method invocation. [Certain methods are exempt (when the class contains a modifier of callstyle=oidl), to maintain upward compatibility for client programs written using an earlier release.]
environment variable. (1.) A variable that describes the operating environment of the process. Common environment variables describe the home directory, command search path, the terminal in use, and the current time zone (the HOME, PATH, TERM, and TZ variables, respectively). (2.) A variable that is included in the current software environment and is therefore available to any called program that requests it.
EOF. End of file.
ephemeral application. An ephemeral application is one which does not contain any recoverable data.
epoch. A timestamp that identifies directory replicas as being part of the same set.
EPOW. Emergency power off warning.
EPROM. Erasable programmable read-only memory.
EPV. See entry point vector or Entry Point Vector.
equivalence class. A grouping of characters or character strings that are considered equal for purposes of collation. For example, many languages place an uppercase character in the same equivalence class as its lowercase form, but some languages distinguish between accented and unaccented character forms for the purpose of collation.
erase. To remove text from a data medium, leaving the medium available for recording new text. See also delete.
erase character. A character that indicates that the previous character on the command line has been erased.
error analysis facility. A program that provides information about the probable cause of errors.
error-checking and correction (ECC). In a processing unit, the detection and correction of all single-bit errors, plus the detection of double-bit and some multiple-bit errors.
error class. Identifies whether an error log entry is for a hardware or software failure.
error condition. The state that results from an attempt to run instructions in a computer program that are not valid or that operate on data that is not valid.
error counter. A type of error entry generated by device driver components. Certain device drivers can generate retry operations if an operation is not successful on the first attempt. They use counters to monitor the number and cause of retry operations, and they contain algorithms that decide when these counters should be sent to the error log.
error device driver. A special file (psuedo device) driver used by the error logging facilities. Error entries are written to the error device driver by the errlog() subroutine and the errsave() kernel service. Error entries are read from the error device driver by the error daemon process and saved in the system error log file.
error ID. See error identifier.
error identifier (error ID). An 8-character code used to identify a particular failure. There is a unique error identifier for each error record template.
error log. (1.) A data set or file in a product or system where error information is stored for later access. (2.) A form in a maintenance library that is used to record error information about a product or system. (3.) A data set used in a processor to record information about certain hardware and programming events. (4.) A record of machine checks, device errors, and volume statistical data.
error log entry. A record in the system error log describing a hardware or software failure and containing failure data captured at the time of the failure.
error message. An indication that an error has been detected.
error output. Synonym for diagnostic output.
error record template. Describes the error class, error type, error description, probable causes, recommended actions, and failure data for an error log entry.
error type. Identifies whether an error log entry is for a permanent failure, temporary failure, performance degradation, impending loss of availability, or undetermined failure.
ESC. See escape character.
escape character (ESC). (1.) In shell programming and TTY programming, the \ (backslash) character, which indicates that the next character is not intended to have the special meaning normally assigned to it. (2.) In general, a character that suppresses or selects a special meaning for one or more characters that follow.
escape function. The code of the form `ESC Something'. One type of multibyte control function.
escape sequence. (1.) A character that is preceded by a \ (backslash) and is interpreted to have a special meaning to the operating system. (2.) A sequence sent to a terminal to perform actions such as moving the cursor, changing from normal to reverse video, and clearing the screen. The terminfo file defines these escape sequences. Synonymous with multibyte control. (3.) Multicharacter code specifying a string variable. See also unescaped.
ESCD console. The ESCD input/output device used to perform connectivity tasks at the ESCD.
ESCON (Enterprise Systems Connection). A System/390 I/O architecture that uses both laser and LED fiber-optic technology and the concept of dynamic connectivity, which allows for path sharing.
ESDI. Enhanced Small Device Interface.
ESN. See entry sequence number.
Ethernet. A 10-megabit baseband local area network using CSMA/CD (carrier sense multiple access with collision detection). The network allows multiple stations to access the medium at will without prior coordination, avoids contention by using carrier sense and deference, and resolves contention by using collision detection and transmission.
evaluation. In Ada language, the evaluation of an expression is the process by which the value of the expression is computed. This process occurs during program execution.
event. (1.) The enqueueing or dequeueing of an element. (2.) An occurrence of significance to a task. (3.) In computer graphics, information generated either asynchronously from a device or as the side-effect of a client request. Events are grouped into types and are not sent to a client by the server unless the client has issued a specific request for information of that type. Events are usually reported relative to a window. See also callback.
event class. A number assigned to a group of trace points that relate to a specific subject or system component. The defined event classes are listed in the trace profile.
event control bit (ECB). A bit assigned to each queue to signal the arrival or departure of an element.
event loop. A sequence of steps performed cyclically to accomplish a task. It must contain at least one input (source) and an ending point.
event manager (EMan). The chief component of the SOM Event Management Framework that registers interest in various events from calling modules and informs them through callbacks when those events occur.
event mask. In computer graphics, the set of event types that a client requests relative to a window.
event queue. In computer graphics, a queue that records changes in input devices--buttons, valuators, and the keyboard. The event queue provides a time-ordered list of input events.
exception. (1.) In programming languages, an abnormal situation that may arise during the running of a program, perhaps causing a deviation from the normal run sequence, and for which handling facilities exist. (2.) An abnormal condition such as an I/O error encountered in processing a data set or a file. (3.) One of five types of errors that can occur during a floating-point exception. These are an operation that was not valid, overflow, underflow, division by zero, and inexact results. (4.) In C++ language, any user, logic, or system error detected by a function that does not itself deal with the error but passes the error on to a handling routine. Passing this error is called throwing an exception. (5.) In Ada language, an error situation which may arise during program execution. To raise an exception is to abandon normal program execution so as to signal that the error has taken place. An exception handler is a portion of program text specifying a response to the exception. Execution of such a program text is called handling the exception. Contrast with interrupt and signal. See also handler and trap handler.
exception handler. (1.) A set of routines used to detect deadlock conditions or to process abnormal condition processing. An exception handler allows the normal running of processes to be interrupted and resumed. (2.) Exception handlers are catch blocks in C++. catch blocks catch exceptions when they are thrown from a function enclosed in a try block. try blocks, catch blocks and throw expressions are the constructs used to implement formal exception handling in C++.
exception handling. A type of error handling that allows control and information to be passed to an exception handler when an exception occurs. try blocks, catch blocks, and throw expressions are the constructs used to implement formal exception handling in C++.
exchange identification (XID). The ID that is exchanged with the remote physical unit when an attachment is first established.
exchange identification (XID) frame. In a logical link control (LLC) header, the frame that conveys the characteristics of the sending host.
exclusive lock. A type of lock in which only the transaction holding the lock can access the data in any way. See also shared locks.
exec. To overlay the current process with another executable program. See also fork.
EXEC. Remote Command Execution Protocol.
executable. A file that can be loaded into memory and executed as a program. An executable is produced by the binder (ld) from one or more object (.o) files. The default processing of compilation commands includes invoking the binder to produce an executable whose name is a.out.
executable file. A file that contains programs or commands that perform operations on actions to be taken.
executable program. A program that can be run as a self-contained procedure. It consists of a main program and, optionally, one or more subprograms.
executable statement. A statement that causes an action to be taken by the program. For example, to calculate, to test conditions, or to alter normal sequential execution.
execute. In CDE, a file or folder (directory) access permission. For files, execute permission enables the user to run a program or shell script file. For folders (directories), execute permission enables the user to access the folder (directory) contents.
existing file. A file that has been defined and that resides on a storage medium.
Exit button. In CDE, a Front Panel control used to log out of the desktop.
exit value. (1.) A code sent to either standard output or standard error on completion of the command. (2.) A numeric value that a command returns to indicate whether it completed successfully. Some commands return exit values that give other information such as whether a file exists. Shell programs can test exit values to control branching and looping.
expanded name. In Ada language, a name that denotes an entity which is declared immediately within some construct. An expanded name has the form of a selected component: the prefix denotes the construct (a program unit; or a block, loop, or accept statement); the selector is the simple name of the entity.
expect-send sequence. In remote communications, a list of characters or signals a program or modem should expect to receive from a remote system, followed by the characters or signals the program or modem should send to the remote system after it receives the expected input. The sequence can also include a subsequence that tells the program or modem what to send if it does not receive the expected input. See also handshaking and chat script.
expedited data negotiation. In X.25 communications, an optional CCITT-specified facility.
expedited data transfer. In X.25 communications, an optional CCITT-specified facility.
expletive. An unnecessary be-verb phrase such as "It is" or "there is" used to begin a sentence or part of a sentence.
explicit binding. A form of binding that gives the client application control over what server machines are involved.
explicit shell. Any of a class of shells created manually by the developer through the Create menu's Shells submenu.
exponent. A number indicating the power to which another number (the base) is to be raised.
exponentiation. The operation in which a value is raised to a power.
export. (1.) In NCS, to provide the operations defined by an interface. A server exports an interface to a client. Contrast with import. (2.) To copy data onto removable media.
exposure event. In Enhanced X-Windows, an event sent to clients to inform them when contents have been lost, as when windows are obscured or reconfigured. Servers do not guarantee the preservation of window contents when they are obscured or reconfigured.
expressed folio. A page numbering style in which each page (possibly excluding the first page) is numbered. See also folio, blind folio, and dropped folio.
expression. (1.) A representation of a value. For example, variables and constants appearing alone or in combination with operators. (2.) In programming languages, a language construct for computing a value from one or more operands, such as literals, identifiers, array references, and function calls. In Ada language, an expression defines the computation of a value. (3.) A configuration of signs.
expression statement. In C language, an expression that ends with a ; (semicolon). You can use an expression statement to assign the value of an expression to a variable or to call a function.
extended address. Synonym for address extension.
extended binary-coded decimal interchange code (EBCDIC). A code developed for the representation of textual data. EBCDIC consists of a set of 256 eight-bit characters.
extended character. A character other than a 7-bit ASCII character. An extended character can be a 1-byte code point with the eighth bit set (ordinal 128 through 255). See also code page and code point.
extended common object file format (XCOFF). The object file format for Version 3 of the operating system. XCOFF combines the standard common object file format (COFF) with the TOC module format concept, which provides for dynamic linking and replacement of units within an object file.
extended curses. A system library(the libcurses.c library) that contains the control functions for writing data to and getting data from the terminal screen. It supports color, multiple windows, and an enhanced character set.
extended family. The set of all of an Ada-language compilation unit's supporters and all of their families, including the associated bodies and subunits. The supporters of a unit include only the library units required for its compilation, not the associated bodies or subunits.
extended font. (1.) A font in which the characters are wider than its corresponding normal font. (2.) A collection of font sections to support languages requiring more than 256 graphic characters at one time.
extended interface. Provides a set of full-function system calls (the readx and writex system calls) to communicate with SNA Server. These calls contain an extra parameter on the call (a pointer to the structure containing extra function requests). See also interface and limited interface.
extended permission. An access mode that modifies the base permissions to a file for specified individuals or groups. An extended permission can deny or permit an access mode. See also discretionary access control.
extended precision constant. A processor approximation to the value of a real number that occupies 16 consecutive bytes of storage and can assume a positive, negative, or zero value. The precision is greater that of type double precision.
extended result. An exception notification that has data defined in the result_ext field of the dlc_getx_arg structure.
extended selection. In CDE, to add multiple items to a selected set by augmenting the selection technique. For example, you can add to a selection by moving the pointer to a new item and pressing Control and the SELECT mouse button simultaneously.
Extended Services. A group of optionally installed operating system functions and programs.
extension. In Enhanced X-Windows, to extend the system, the named extensions can be defined for the Core protocol, including extensions to output requests, resources, and event types.
extent. (1.) A continuous space on disk or diskette that is occupied by or reserved for a particular data set, data space, or file.
exterior gateway. A gateway on one autonomous system that communicates with other autonomous system.
external clocking. In data communications, the ability of a modem to provide data clocking.
external data definition. A description of a variable appearing outside a function. It causes the system to allocate storage for that variable and makes that variable accessible to all functions that follow the definition and are located in the same file as the definition.
eXternal Data Representation (XDR). A standard for the description and encoding of data; it uses a languages to describe data formats, but the language is used only for describing data and is not a programming language. Protocols such as RPC and NFS use XDR to describe their data formats.
external function. In FORTRAN, synonymous with external routine.
external modem. A modem that is separate from the unit with which it operates.
external name. (1.) A name that can be referred to by any control section or separately assembled or compiled module; a control section name or an entry name in another module. (2.) In a program, a name whose scope is not necessarily confined to one block and its contained blocks.
external procedure. Synonymous with external routine.
external reference. A reference to a symbol defined as an external name in another program or module.
external routine. A procedure or function called from outside the program in which the routine is defined. Synonymous with external procedure.
external symbol. A symbol that is defined in a file other than the file in which the symbol occurs. An ordinary symbol that represents an external reference.
external variable. A variable accessible to another compilation unit. See also compilation unit.
extract. To obtain. For example, to extract information from a file.
eye coordinates. In GL, the coordinate system in which the viewer's eye is located at the origin, and thus all distances are measured with respect to the eye. Viewing transformations map from world coordinates into eye coordinates, and projection transformations map from eye coordinates to normalized device coordinates. Synonym for eye space, viewing coordinates, and viewer coordinates. See also modeling coordinates, primitive coordinates, world coordinates, screen coordinates, and transformation.
eye space. Synonym for eye coordinates.