C

C. Celsius or country.

C interface. The interface, defined at a level that depends on the variant of C standardized by ANSI.

C language. A general-purpose programming language that is the primary language of the operating system.

C library. A system library that contains common C language subroutines for file access, string operators, character operations, memory allocation, and other functions.

C++ language. A programming language based on the C language and developed by Bjarne Stroustrup. C++ defines data types called classes. Classes provide data abstraction and are composed of data (data members) and operations that operate on that data (member functions). C++ also implements the object-oriented programming concepts of inheritance through class derivation and polymorphism through virtual functions and overloading.

C++ language statement. A C++ language statement contains zero or more expressions. All C++ language statements, except block statements, end with a ; (semicolon) symbol. A block statement begins with a { (left brace) symbol, ends with a } (right brace) symbol, and contains any number of statements.

C++ library. A system library that contains common C++ language subroutines for file access, memory allocation, and other functions.

cable. The physical media for transmitting signals; includes copper conductors and optical fibers.

cache. (1.) A high-speed buffer storage that contains frequently accessed data or instructions and that can deliver that data or instructions faster than the storage medium on which that information usually resides. A cache is used to reduce access time. See also write back cache. (2.) To place, hide, or store in a cache. A technique (usually software-based) whereby high-speed storage that is not immediately required for other purposes is used to retain data that has been loaded into it once, in the hope that another request for the data will occur before the high-speed storage must be reassigned.

cache coherency. The need to ensure that multiple threads on multiple processors changing a single cache line do not create inconsistent versions of the cache line in the different caches.

cache hit. A processor storage reference that is satisfied by information from a cache.

cache line. The cache component that is normally loaded, stored, and interrogated during cache lookup.

cache line tag. The information kept with each cache line to identify the part of virtual storage it contains.

cache lookup. The process of determining whether or not a cache contains the information necessary to satisfy a storage reference. A defined set of bits in the address being referenced identifies the line or lines to be interrogated.

cache miss. (1.) A delay that occurs when the CPU references data or instructions that are not already in the data cache or instruction cache. (2.) A processor storage reference that cannot be satisfied from a cache and therefore requires a RAM access.

CAD/CAM. Computer-Aided Design/Computer-Aided Manufacturing.

CAI. See computer-aided instruction.

Calculator. In CDE, a software application that mimics the function of a handheld calculator.

Calendar. In CDE, a software application that enables you to schedule appointments and create To Do lists.

Calendar view. In CDE, the day, week, month, or year displayed in the main Calendar window.

call. (1.) To activate a program or procedure, usually by specifying the entry conditions and jumping to an entry point. See also load. (2.) In data communications, the action necessary in making a connection between two stations on a switched line. (3.) In X.25 communications, a conversation between two users.

call-accepted packet. In X.25 communications, a call supervision packet transmitted by a called DTE to inform the DCE of the acceptance of the call.

call-back. A characteristic of the UUCP file USERFILE that tells a remote system whether the local system it tries to access will call back to check its identity.

call collision. See collision.

call-connected packet. In X.25 communications, a call supervision packet transmitted by a DCE to inform the calling DTE of the complete establishment of the call.

call redirection notification. In X.25 communications, an optional CCITT-specified facility that informs the caller that the call has been redirected to another DTE.

call request (CRQ). A signal sent by a computer to request from data communications equipment that a communications connection be established with another computer in the network.

call-request packet. In X.25 communications, a call supervision packet transmitted by a DTE to ask for a call establishment through the network.

call user data (CUD). In X.25 communications, data optionally included in the call-request packet by the user application.

callback. (1.) A procedure that is called if and when certain specified conditions are met. This is accomplished by specifying the procedure in a callback list. Synonymous with callback function. (2.) In SOM, a user-provided procedure or method to the Event Management Framework that gets invoked when a registered event occurs. (See also event).

callback function. Synonym for callback.

callback list. (1.) A list of procedures that are called if and when certain specified conditions are met. (2.) In AIXwindows, individual widgets can define callback lists as required.

callback reason. The conditions that, if met, result in a callback procedure being called.

callback routine address. The internal address of a given callback routine.

callback routines. Procedures that are called if and when certain specified conditions are met. See also callback.

called. In X.25 communications, an adjective applied to the location or user to which a call is made.

called address extension. See address extension.

called DLS user. The data link service (DLS) user in connection mode that processes requests for connections from other DLS users.

called line address modified notification. In X.25 communications, an optional CCITT-specified facility.

called NS user . A network service (NS) with whom a calling NS user wants to establish a network connection.

called subaddress. See subaddress.

calling. In X.25 communications, an adjective applied to the location or user that makes a call.

calling address. See network user address.

calling address extension. See address extension.

calling conventions. Specified ways for routines and subroutines to exchange data with each other.

calling DLS user. The data link service (DLS) user in connection mode that initiates the establishment of a data link connection.

calling NS user . A network services (NS) user that initiates a network connection.

calling tree. The tree of control of a program. The main procedure is the calling tree's trunk; any procedure referenced by the main procedure branches off from the trunk, and any procedure referenced by another procedure is a branch off that branch. A branch that does not reference other procedures is known as a leaf.

callout. A kernel parameter that establishes the maximum number of scheduled activities that can be pending simultaneously.

callout table. A kernel table that keeps track of all sleeping processes and the channel on which each is waiting.

cancel. To end a task before it is completed.

Cancel. In CDE, a push button that removes a window without applying any changes made in that window.

canonical processing. Processing that occurs according to a defined set of rules. This is the style of input that is typically used by the shell and simple commands.

caps. (1.) Capital letters, an uppercase font. (2.) A printing style that uses two type sizes of a single uppercase font. The smaller size is used instead of a lowercase font.

caption. Text associated with, and describing, a table or figure.

capture. To digitize an image into the video memory of the M-Video Capture Adapter.

capture file. A file used by a communications program to capture, or record, data coming in over a connection to a remote system or device.

capture key. A toggle control key that starts or stops the process of saving the data displayed on the screen during an active connection.

card. An electronic circuit board that is plugged into a slot in the system unit. See also adapter.

cardinal spline cubic curve. In computer graphics, a cubic spline whose endpoints are the second and third of four control points. A series of cardinal splines have a continuous slope and pass through all but the first and last control points. See also parametric cubic curve.

carriage return. (1.) In text data, the action that indicates to continue printing at the left margin of the next line. A carriage return is equivalent to the carriage return of a typewriter. (2.) A keystroke generally indicating the end of a command line.

carrier. In data communication, a continuous frequency that can be modulated or impressed with an information-carrying signal.

carrier sense multiple access with collision detection (CSMA/CD). The generic term for a class of medium access procedures that allows multiple stations to access the medium at will, without explicit prior coordination, and avoids contention by way of carrier sense and deference. Contention is resolved by way of collision detection and transmission.

carrier signal. A signal with a constant frequency that can be modulated to carry a data signal.

cascade button. In AIXwindows, a rectangular graphic control that can be made to appear from behind another graphic control to provide an additional option or range of options.

cascading menu. A submenu of related choices that is invoked when the parent item, is selected. Usually, a choice that offers a cascading menu is designated by an arrow to the right of the choice. Similar to a context line.

case clause. In a C For AIX switch statement, a case label followed by any number of statements.

CASE. Computer Assisted Software Engineering. A set of tools or programs to help develop complex applications.

CASE label. In Pascal, a value or range of values that comes before a statement in a CASE statement branch. When the selector is evaluated to the value of a CASE label, the statement following the case label is processed.

case label. The word case followed by a constant expression and a colon. When the selector is evaluated to the value of the constant expression, the statements following the case label are processed.

case-sensitive. Able to distinguish between uppercase and lowercase letters.

cast. In C language, an expression that converts the value of the operand to a specified scalar data type (the operator).

casted dispatching. In SOM, a form of method dispatching that uses casted method resolution; that is, it uses a designated ancestor class of the actual target object's class to determine what procedure to call to execute a specified method.

casted method resolution. In SOM, a method resolution technique that uses a method procedure from the method table of an ancestor of the class of an object (rather than using a procedure from the method table of the object's own class).

C.A.T. Computer-assisted typesetting.

catalog. A set of predefined components and attributes used to create Interleaf documents.

catastrophic cancellation. A programming error in which values with very large negative exponents are added or multiplied together until a zero value is produced, which is then propagated into successive computations.

catch block. A block in a C++ program that receives control when an exception matching its argument is thrown. Each catch block is associated with a try block.

cathode ray tube (CRT). A vacuum tube in which a beam of electrons can be moved to draw lines or to form characters or symbols on its luminescent screen.

cause code. In X.25 communications, a 1-byte code included in clear- and reset-indication packets that indicates the origin of the packet and the reason for sending it. Synonymous with clear cause. See also diagnostic code.

CBEMA. Computer and Business Equipment Manufacturers Association.

CCITT. Comite Consultatif International Telegraphique et Telephonique. See Consultative Committee on International Telegraphy and Telephone.

CCW. Channel control word. This is a defined control encoding that is used to control the operations of I/O units on the System 360/370 channel.

CD. Carrier detect. See also DCD.

CDE. An acronym for Common Desktop Environment, a graphical user interface running on UNIX.

CDLI. Common Data Link Interface. Device drivers that interface with kernel services to provide support for sockets and STREAMS interfaces.

CD-ROM. High-capacity read-only memory in the form of an optically read compact disc.

CDS. Cell Directory Service.

CDS-defined attribute. A standard attribute that CDS associates with names. A specific CDS-defined attribute has the same meaning no matter what type of entry (clearinghouse, directory, object) it is associated with. However, different types of entries can have different CDS-defined attributes. For example, every CDS name has the CDS-defined attributes of Creation Timestamp (CDS_CTS), Update Timestamp (CDS_UTS), and Access Control Set (CDS_ACS). In addition to those attributes, a soft link has unique CDS-defined attributes containing its expiration time and the name it points to.

CDS directory. A logical unit for storing entries under one name (the directory name) in a CDS namespace. In addition to object entries, a directory can contain soft links and child pointers. You can copy, delete, and control access to a directory. Each physical instance of a directory is called a replica.

CDSPI. Cell Directory Service Portable Interface.

CDSTL. See connect data set to line.

CEC. Central Electronics Complex.

cell. The rectangular juncture of a horizontal row and a vertical column. Examples include the cells of an electronic spreadsheet and the cells utilized by an XmRowColumn widget in an AIXwindows graphic interface. In Interleaf, a table cell is actually a modified frame that can contain data.

cell-relative name. See local name.

centered dot. A heavy bullet used as a mark to set off a paragraph or list item.

central processing unit (CPU). The part of a computer that includes the circuits that control the interpretation and running of instructions.

CFM. Cubic feet per minute.

CGA. Color Graphics Adapter.

CGM. See Computer Graphics Metafile.

change bit. A bit in each page-frame table entry that denotes the corresponding page has been written to since the last time the operating system cleared the page.

channel. (1.) A path along which signals or data passes. (2.) The portion of a storage medium that is accessible to a given reading or writing station. (3.) In data communication, a means of one-way transmission. (4.) A functional unit, controlled by a host computer, that handles the transfer of data between processor storage and local peripheral equipment. (5.) The system element that controls a single channel path, whose mode of operation depends on the type of hardware to which it is attached. (6.) A device connecting the processor to input and output devices. (7.) One of 32 bits in a table used to represent which event classes are active or inactive. The most significant bit is called channel 0 and the least significant bit is called channel 31. See also logical channel.

channel control word. See CCW.

channel ID. A channel identification passed back from a multiplexed device to the file system as a result of calling the ddmpx entry point.

channel number. A number that identifies the path by which data is transferred between a particular input or output device and the processor of the computer. The major device, minor device, and channel numbers uniquely identify a hardware device.

channel path. A single interface attaching one or more control units.

channel-path Identifier (CHPID). In a System/390 channel subsystem, a value assigned to each installed channel path of the system that uniquely identifies that path to the system.

char. In Object Database Manager, a terminal descriptor used to define a variable as a fixed-length, null-terminated string. See also terminal descriptor.

char specifier. The keywords char and unsigned char, which describe the type of data a variable represents.

character. A letter, digit, or other symbol.

character cell. The physical width and height in pels of a font. See also bounding box.

character class. (1.) Ranges of characters that match a single character in the input stream. (2.) A set of characters enclosed in sequence, or square [], brackets.

character constant. (1.) A constant value whose data attribute is character. (2.) In programming languages, a character or an escape sequence enclosed in single quotation marks.

character data indexing. An input/output optimization that reduces I/O access time by searching for a string in a small index file, and using the obtained index to find a record in the main data file.

character delete. In text data, the action that erases the character at the current cursor location and moves any trailing text one character position to the left.

character device. A device that handles data one character at a time. See also character special file.

character display. A display that uses a character generator to display predefined character boxes of images (characters) on the screen. This kind of display cannot address the screen any less than one character box at a time. Contrast with All Points Addressable display.

character expression. A character constant or variable, character array element, character substring, character-valued function reference, or sequence of the preceding separated by the concatenation operator, with optional parentheses.

character graphics. (1.) The visual representation of a character, defined by toned or intoned picture elements (pels). (2.) Graphics that are composed of symbols printed in a monospace font. Some symbols are standalone; others are intended for assembling larger figures.

character key. (1.) A keyboard key that allows the user to enter the character shown on the key. See also function keys. (2.) In word processing, a control used to process text one character at a time.

character literal. A symbol, quantity, or constant in a source program that is itself data, rather than a reference to data. Contrast with numeric literal.

character position. On a display, the location of a character.

character set. A group of characters used for a specific reason; for example, the set of characters a printer can print or a keyboard can support.

character special file. A special file that provides access to an input or output device. The character interface is used for devices that do not use block I/O. See also block file, special file, and block special file.

character string. A sequence of consecutive characters. In the C programming language, a string must be null-terminated.

character substring. A contiguous portion of a character string.

character translation. In international character support, the dd command and various conversion subroutines that translate between extended characters and ASCII escape strings to preserve unique character information.

character type. A data type that consists of alphanumeric characters. See also data type.

character variable. In the C language, a data object whose value can be changed during the running of a program and whose data type is char or unsigned char.

characteristic attribute. A type of attribute that reflects or affects the behavior of a software entity. You generally can set or change characteristic attributes.

charging requesting service. In X.25 communications, an optional facility that specifies that charging information (segment count data, monetary unit data, or call duration data) is required.

chat script. In remote communications, a list of expect-send sequences that a modem uses to establish a communication link with another modem. See also handshaking and expect-send sequence.

checkbox. A small square box that can be turned on or off to indicate the state of an option.

checkpoint. A snapshot of the current state of the recoverable data being used by an application. Checkpoints are used to capture the state of recoverable data between backups, thus minimizing the time involved in restarting systems which use that data by providing a more recent image of that data.

checksum. (1.) The sum of a group of data associated with the group and used for checking purposes. (2.) On a diskette, data written in a section for error detection purposes.

child. (1.) Pertaining to a secured resource, either a file or library, that uses the user list of a parent resource. A child resource can have only one parent resource. (2.) In the operating system, a child is a process, started by a parent process, that shares the resources of the parent process. Contrast with parent. (3.) In Enhanced X-Windows and AIXwindows, a first-level subwindow. A widget managed by another widget is said to be the child of the managing parent widget. For example, Composite widgets typically manage the Primitive children widgets attached to them. The parent widget typically controls the placement of the child as well as when and how it is mapped.

child class. A SOM class that inherits instance methods, attributes, and instance variables directly from another class, called the parent class, base class, or superclass, or indirectly from an ancestor class. A child class may also be called a derived class or subclass.

child device. A hierarchical location term. It indicates what can be connected to a parent device. For example, an SCSI disk can be a child device of an SCSI adapter.

child gadget. A windowless child widget. See also child widget.

child process. In the operating system, a process, started by a parent process, that shares the resources of the parent process.

child resource. Pertaining to a secured resource, either a file or library, that uses the user list of a parent resource. A child resource can have only one parent resource.

child widget. In AIXwindows and Enhanced X-Windows, a widget managed by another widget is said to be the child of the managing parent widget. For example, Composite widgets typically manage the Primitive children widgets attached to them. The parent widget typically controls the placement of the child as well as when and how it is mapped. When a parent widget is deleted, all the children controlled by that parent are automatically deleted as well.

children. Plural of child.

children spacing. In AIXwindows and Enhanced X-Windows, widgets managed by another widget are said to be the children of the managing parent widget. The parent widget typically controls the physical spacing and placement of the children within the border of the parent.

choice. An option in a pop-up or menu used to influence the operation of the system.

chord. In graphics, a short line segment whose end points lie on a circle. Chords are a means for producing a circular image from straight lines. The higher the number of chords per circle, the smoother the circular image.

CHPID. Channel path identifier.

CICS. See Customer Information Control System.

CID. See connection identifier.

ciphertext. The output of an encryption function. Encryption transforms plaintext into ciphertext.

circuit. See virtual circuit.

circuit switching. A process that, on demand, connects two or more data terminal equipments (DTEs) and permits the exclusive use of a data circuit between them until the connection is released.

C-ISAM. C-language Indexed Sequential Access Method.

CLA. See communications line adapter.

class. (1.) Pertains to the I/O characteristics of a device. In this operating system, devices are classified as block or character. (2.) In Enhanced X-Windows, a general group to which a specific object belongs. See also widget class. (3.) In AIXwindows, an object-oriented data structure containing generalized information about a group of similar graphical objects known as widgets or gadgets. Each class of graphical objects inherits some or all of the appearance characteristics and behavior characteristics of the classes that precede it in the object hierarchy. (4.) A C++ class is a user-defined data type. A class data type can contain both data representations (data members) and functions (member functions). See also object class. (5.) In SOM, a way of categorizing objects based on their behavior (the methods they support) and shape (memory layout). A class is a definition of a generic object. In SOM, a class is also a special kind of object that can manufacture other objects that all have a common shape and exhibit similar behavior. The specification of what comprises the shape and behavior of a set of objects is referred to as the "definition" of a class. New classes are defined in terms of existing classes through a technique known as inheritance. See also class object.

class data structure. A structure provided by the SOM API to support efficient static access to class-specific information used in dealing with SOM objects. The structure's name is <className>ClassData. Its first component (classObject) is a pointer to the corresponding class object. The remaining components (named after the instance methods and instance variables) are method tokens or data tokens, in order as specified by the class's implementation. Data tokens are only used to support data (public and private) introduced by classes declared using OIDL; IDL attributes are supported with method tokens.

class key. One of the C++ keywords: class, struct, and union.

class library. A collection of C++ classes.

class manager. An object that acts as a run-time registry for all SOM class objects that exist within the current process and which assists in the dynamic loading and unloading of class libraries. A class implementor can define a customized class manager by subclassing SOMClassMgr class to replace the SOM-supplied SOMClassMgrObject. This is done to augment the functionality of the default class-management registry (for example, to coordinate the automatic quiescing and unloading of classes).

class member operators. Used to access C++ class members through class objects or pointers to class objects. They are ., ->, .*, and ->*.

class method. Also known as factory method or constructor.) A SOM class method is a method that a class object responds to (as opposed to an instance method). A class method that class <X> responds to is provided by the metaclass of class <X>. Class methods are executed without requiring any instances of class <X> to exist, and are frequently used to create instances of the class.

class name. (1.) For widgets and gadgets, the name in the code corresponding to the resource database containing the generic properties for all objects in the class. (2.) A unique identifier of a C++ class type that becomes a reserved word within its scope.

class object. The run-time object representing a SOM class. In SOM, a class object can perform the same behavior common to all objects, inherited from SOMobject.

class record. A particular widget record that contains the data objects pertaining to the class of any given widget. See also record, widget record, and class.

class scope. The scope of C++ class members.

class template. A blueprint describing how a set of related C++ classes can be constructed.

class variable. In SOM, instance data of a class object. All instance data of an object is defined (through either introduction or inheritance) by the object's class. Thus, class variables are defined by metaclasses.

CLAW. See Common Link Access to Workstation.

clean up. The clean-up procedure instructs the system to attempt to remove software products that were partially installed. The system also attempts to revert to the previous version of the removed product. If the system successfully reverts to the previous version, it becomes the currently active version. If this cannot be done, then the software product is marked as broken. After the clean-up procedure is complete, you can attempt to install the software again.

clean-up code. In loops that have been unrolled or blocked, an additional loop or set of loops that ensures that all iterations of the original code are executed in the unrolled or blocked code.

clear. In X.25 communications, to reject a call (if it has not yet been accepted) or end a call.

clear cause. See cause code.

clear collision . A condition that occurs when a STE and a DCE simultaneously transmit a clear request packet and a clear indication packet over the same logical channel. See also collision.

clear-confirmation packet. In X.25 communications, a packet transmitted by the DTE to inform the DCE that a call has been cleared

clear diagnostic. See diagnostic code.

clear-indication packet. In X.25 communications, a call supervision packet transmitted by a DCE to inform a DTE of the clearing of a call.

clear-request packet. In X.25 communications, a call supervision packet transmitted by a DTE to ask for a call to be cleared.

clear user data. In X.25 communications, data optionally included in the clear-request packet by the user application.

click. In CDE, to press and release a mouse button without moving the mouse pointer. Unless otherwise specified, mouse button 1 is assumed.

client. (1.) In a distributed file system environment, a system that is dependent on a server to provide it with programs or access to programs. (2.) In Enhanced X-Windows, an application program that connects to an Enhanced X-Windows server by an inter-process communication (IPC) path, such as a Transmission Control Protocol (TCP) connection or a shared memory buffer. The program can be referred to as the client of the server, but it is actually the IPC path itself. Programs with multiple paths open to the server are viewed as multiple clients by the protocol. (3.) In Enhanced X-Windows, a Toolkit routine that uses a widget in an application or for composing another widget. (4.) In AIXwindows, a software application that fills the role of the client in the traditional client-server model upon which Enhanced X-Windows and AIXwindows are based. See also client application. (5.) In NCS, a program that uses an interface to make remote procedure calls (RPCs).

client agent. See Location Broker Client Agent.

client application. A type of application. See also application.

client code. (Or client program or client.) A SOM application program, written in the programmer's preferred language, which invokes methods on objects that are instances of SOM classes. In DSOM, this could be a program that invokes a method on a remote object.

client program. A program that uses a C++ class. The program is said to be a client of the class.

client-side caching. A high-speed buffer storage that contains frequently accessed information associated with a client application. The primary purpose of client-side caching is to reduce access time to key information.

clip. In computer graphics, to remove those parts of a display image that lie outside of a given boundary.

clip list. In Enhanced X-Windows, a list of rectangles designated for clipping.

clipboard. A storage space set aside for the temporary storage and retrieval of text or graphics during cut-and-paste operations. Data in the clipboard is available to other applications.

clipboard selection. Data selected and pasted to the clipboard that can be pasted or passed to a function. Data can include such elements as text, graphics, and widgets.

clipping. In GL, if a primitive overlaps the boundaries of a window, it is clipped. The part of a primitive that appears in the window is displayed and the rest is ignored. There are several types of clipping that occur in the system. Three-D drawing primitives are clipped to the boundaries of a frustum (for perspective transformations) or to a rhombohedron (for orthographic projections). This 3-D clipping applies as well to the origin of character strings, but not to the characters themselves. A 2-D clipping is also performed, where all drawing is clipped to the boundaries of the AIXwindows window. The area of 2-D clipping can be controlled with the screenmask. See also clipping planes, fine clipping, gross clipping, screenmask, transformation, and window.

clipping planes. In GL, before clipping occurs, primitive space is mapped to normalized device coordinates. The clipping planes x=+/-w; y=+/-w; or z=+/-w correspond to the left, right, top, bottom, near, and far planes bounding the viewing frustum. See also frustum.

clipping region. In Enhanced X-Windows, a type of graphics output. In a graphics context, the image defined by the bitmap or rectangles used to restrict output to a particular region of a window.

CLK. See clock.

Clock. In CDE, a Front Panel control that displays the local time.

clock (CLK). (1.) A device that generates periodic signals used for synchronization. (2.) In data communication, equipment that provides a time base used in a transmission system to control the timing of certain functions, such as sampling, and to control the duration of signal elements.

clocking. (1.) In binary synchronous communication, the use of clock pulses to control synchronization of data and control characters. (2.) In data communications, a method of controlling the number of data bits sent on a communications line in a given time.

clone device. A STREAMS device that returns an unused major or minor device when initially opened, rather than requiring the minor device to be specified by name in the open call.

close. (1.) To end an activity and remove that window from the display. (2.) A data manipulation function that ends the connection between a file and a program. Contrast with open.

closed user group (CUG). In X.25 communications, a subgroup of users that is assigned to a facility that enables a member of one subgroup to communicate only with other members of the subgroup. A DTE can belong to more than one closed user group. See also bilateral closed user group.

cluster. (1.) Any configuration of interconnected workstations for the purpose of sharing resources (for example, local area networks, host attached workstations, and so on). (2.) A group of storage locations allocated at one time. (3.) A station that consists of a control unit (cluster controller) and the workstations attached to it. (4.) A page-size (4096-byte) buffer provided by the mbuf management facility to the various layers of communication software in AIX. (Also called "cluster mbuf," "mbuf cluster," and "mapped page.")

clustered file. Files in which records with adjacent key values are physically clustered together. The clustered file organization optimizes sequential access through the primary index to records in the file.

CMOS. Complementary metal-oxide semiconductor. CMOS is a technology that combines the electrical properties of n-type semiconductors and p-type semiconductors.

coaxial cable. A cable consisting of one conductor, usually a small copper tube or wire, within and insulated from another conductor of larger diameter, usually copper tubing or copper braid.

COBOL. Common business-oriented language. A high-level programming language, based on English, that is used primarily for business applications.

code. (1.) Instructions to the computer. (2.) To write instructions for the computer; to program. (3.) A representation of a condition, such as an error code.

code page. (1.) An assignment of graphic characters and control function meanings to all code points. (2.) Arrays of code points representing characters that establish the ordinal sequence (numeric order) of characters. This operating system uses 256-character code pages. See also code point and extended character. (3) An ordered set of up to 256 predefined display symbols. The first 32 code points of each code page are reserved for control codes and are the same for all code pages, leaving up to 224 distinct display symbols per page.

code point. A character within a code page.

code segment. See segment.

code server. A system that is providing a code service for other computers on a network.

code set. In the XPG4 system interface, a set of unambiguous rules that establish a character set and the one-to-one relationship between each character of the set and its bit representation.

col. A typesetter postprocessor that buffers typeset output to allow printing on printers and workstations that do not support backscrolling.

collapse. To remove the contents of a directory from the display (close it) using the CDS Browser. To collapse an open directory, you double-click on its icon. Double-clicking on a closed directory expands it.

collating element. One or more characters that match a sequence in a regular expression.

collating sequence. The sequence in which characters are ordered within the computer for sorting, combining, or comparing.

collation. The process of character and string sorting based on alphabetical order and equivalence class.

collation table. Provides an ordered character set and character equivalence classes used by functions.

collection. In Ada language, the entire set of objects created by evaluation of allocators for an access type.

colliding find request. A condition that occurs when two link stations attempt to call each other at the same time.

collision. (1.) An unwanted condition caused by concurrent transmissions on the medium that results in garbled data. (2.) In X.25 communications, a condition that occurs when a DTE and a DCE simultaneously transmit packets (for instance, a clear-request packet and a clear-indication packet) over the same logical channel. This can be a clear collision, call collision, or reset collision.

colon format. A format into which data files can be organized. Each data record consists of one line in the colon file, and data fields in each data record are separated by colons.

color cell. In Enhanced X-Windows, an entry in a colormap that consists of three values based on red, green, and blue intensities. The values are 16-bit, unsigned numbers. Zero represents the minimum intensity. The values are scaled by the server to match the particular display in use.

color display. A display device capable of displaying more than two colors and the shades produced by combinations of two colors, as opposed to a monochrome display.

color expansion operation. A graphics programming operation that occurs automatically when the source pixel map data area contains only 1 byte per pixel and the destination pixel map data area is a color display adapter buffer frame defined to have more than 1 bit per pixel.

color graphics adapter. An adapter that allows a computer to use a color display.

color lookup table. Synonym for color map.

color map. (1.) In computer graphics, a lookup table where each index is associated with a red, green, and blue value. Synonymous with color lookup table, color palette, and color table. (2.) In Enhanced X-Windows, a set of color cells. A pixel value indexes the color map to produce RGB-value intensities. A color map consists of a set of entries defining color values that, when associated with a window, is used to display the contents of the window. Depending on hardware limitations, one or more color maps can be installed at one time such that windows associated with those maps display correct colors. The two classes of color maps are direct color and pseudocolor. (3.) In GL, a lookup table that translates color indexes into RGB triplets. The lookup table is sandwiched between the frame buffer and the digital-to-analog converters (DACs) and serves to translate the color index value stored in the frame buffer into the red, green, and blue values required by the DACs. On most hardware configurations, the color map is either 8 or 12 bits deep, allowing the simultaneous display of 256 or 4096 colors. On most hardware configurations, the DACs have an 8-bit per color accuracy, allowing the user to choose among 16,777,216 colors.

color map mode. A configuration of the hardware that passes the values stored in the frame buffer through a color lookup table (color map), from which the red, green, and blue values are obtained for display. Entries in the color map are referred to as color indexes. In color map mode, the values stored in the frame buffer are treated as color map indexes. See also RGB mode.

color palette. Synonym for color map.

color ramp. A progression of colors in a color map. Most color ramps are smooth and have only a small number, if any, of discontinuities. For instance, if the full set of colors of the rainbow were loaded into the color map, that would constitute a color ramp.

color table. Synonym for color map.

color viewer. In AIXwindows, an interface that allows the user to choose a color as a value for a widget property.

column. A vertical arrangement of characters or other expressions.

column headings. Text appearing near the top of a column of data for the purpose of identifying or titling the data in the column.

column inch. A unit of measure for printed text. One column inch is the amount of text contained in an inch of type depth, one column wide.

column-major order. A way of storing array elements such that the leftmost subscript varies most rapidly as memory-adjacent elements are accessed.

combined I and D cache. A cache that contains both instructions and data, distinguishable only by the cache line tag.

comma expression. An expression that contains two operands separated by a comma. Although the compiler evaluates both operands, the value of the right operand is the value of the expression. If the left operand produces a value, the compiler discards this value.

command. (1.) A request to perform an operation or run a program. When parameters, values, flags, or other operands are associated with a command, the resulting character string is a single command. (2.) In data communication, an instruction represented in the control files of a frame and transmitted by a primary or combined station. It causes the addressed station to run a data link control function.

command frame. A link-level frame or packet that is serviced as a command and (in most cases) expects a response.

command history. An automatic listing of previously issued commands.

command interpreter. A program that sends instructions to the kernel. Synonym for interface. See also shell.

command line. The area of the screen where commands are displayed as they are typed.

command line editing keys. Keys for editing the command line.

command mode. A state of a system or device in which the user can enter commands.

command module. A file that executes a command or process. The file may be activated when the user enters a command at the command line or by another command module.

command name. (1.) The first or principal term in a command. A command name does not include parameters, values, flags, or other operands. (2.) The full name of a command when an abbreviated form is recognized by the computer (for example, print working directory for pwd).

command programming language. Facility that allows programming by the combination of commands rather than by writing statements in a conventional programming language.

command string. A request to perform an operation, along with the operands that provide all instructions needed for running the operation.

command substitution. The ability to capture the output of any command as a value to another command by placing that command line within ` ` (grave accents). The shell first runs the command or commands enclosed within the grave accents and then replaces the whole expression, including grave accents, with their output. This feature is often used in assignment statements.

command word. The name of the 16-bit units used for storing graphic primitive strings. The first command word determines the primitive type and sets the length of the string. Subsequent command words contain information in multiples of quid, or 4 bits of data.

commit. (1.) To make permanent all changes that have been made to the database file since the last commitment operation and to unlock the records so they are available to other users. Contrast with reject. (2.) When you commit software, you are making a commitment to that version of the software product. When you commit a product, the saved files from all previous versions of the software product are removed from the system, thereby making it impossible to return to a previous version of the software product. In SMIT, software can be committed at the time of installation by setting the COMMIT software? question to yes (or by using the -ac flags with the installp command). Note that committing already applied software does not change the currently active version of the software product. It merely removes saved files for the previous version of the software product. The rejection of the installation level of the product does not have the same meaning as the rejection of updates to the product. Once you commit a new version of a product, you must reinstall the previous version if you want to use that version again. Compare to apply and contrast with reject and remove.

commit operation. An operation that saves a file to permanent storage.

common block. In FORTRAN, a storage area that can be referred to by a calling program and one or more subprograms.

common carrier. Any government-regulated company that provides communication services to the general public.

Common Link Access to Workstation (CLAW). The architecture that defines the channel commands used between the host and the channel attachment adapter.

common subexpression enhancement. An optimization that enables a compiler to detect that two or more distinct subexpressions within an expression or loop are identical and need only be computed once.

communications. The transmission of data according to a protocol between computers or remote devices, usually over a long distance.

communications adapter. A circuit card with associated software that enables a processor, controller, or other device to be connected to a network. See also adapter.

communications authority password. One of the two communications security passwords. It controls access to communication configuration menus so that only authorized persons can change the profiles, encrypt a portion of the communication profile database, or control the startup of SNA processes. The password must be a 30-to-80-character phrase, with interior blanks allowed. See also BIND password.

communications channel. An electrical path that facilitates transmission of information from one location to another.

communications co-processor. A microprocessor on an expansion board that supplements the operations of the processor in the system unit, enabling a computer to use communication services in parallel with other operations.

communications endpoint. In X.25, the local communication channel between a DLS user and a DLS provider.

communications line. The line over which data communications take place; for example, a telephone line. See also X.25 line.

communications line adapter (CLA). A functional unit that converts the serial-by-bit output of a station to a parallel bit form and from a parallel bit form to serial-by-bit input to a station.

communications link. See data link.

communications service. The service performed by the Sockets Application Programming Interface, which allows data packets to be delivered to the specified destination. There are three types of communications services offered: reliable stream delivery, connectionless datagram delivery, and raw socket delivery.

compatibility. (1.) The ability to perform tasks identically in different environments without major modifications. (2.) The capability of a functional unit to meet the requirements of a specified interface.

compatible. Pertaining to computers on which the same program can be run without appreciable alteration.

compatible types. Different data types that can be operands for the same operation.

compilable unit. In Pascal, synonymous with compilation unit.

compilation. In Ada language, a compilation is generally the translation of an Ada source program into an executable object module. When using the Ada language debugger, a compilation consists of one or more compilation units in a single file. If you include three package specifications and two package bodies in one file, that file represents one compilation consisting of five compilation units: three library units and two secondary units. There is usually only one compilation unit in a compilation.

compilation time. The time during which a source program is translated from a high-level language into a machine language.

compilation unit. A portion of a computer program sufficiently complete to be compiled correctly. In Pascal, there are two types of units: the program unit and the segment unit. In Ada language, a compilation unit is the declaration or the body of a program unit, presented for compilation as an independent text. It is optionally preceded by a context clause, naming other compilation units upon which it depends by means of one more with clauses.

compile. To translate a program written in a high-level programming language into an intermediate language, assembly language, or a machine language.

compiler. (1.) A program that translates a source program into an executable program (an object program). (2.) A program that translates instructions written in a high-level programming language into machine language.

compiler directing statement. Synonym for compiler directive.

compiler directive. A statement that controls what the compiler does rather than what the user program does.

complement of a number. The value that when added to the number equals a given value.

complete class name. The complete qualification of a nested C++ class name including all enclosing class names.

complete overwrite installation. An installation method that completely overwrites an existing version of BOS that is installed on your system. This procedure may impair recovery of data or destroy all existing data on your hard drives. Be sure to back up your system before doing a complete overwrite installation.

complete packet sequence. Either an individual X.25 data packet or a sequence of packets with the M-bit set to 1 and the D-bit set to 0, followed by a further data packet with the M-bit set to 0 and the D-bit set as required.

complex constant. In FORTRAN, an ordered pair of real or integer constants separated by a comma and enclosed in parentheses. The first constant of the ordered pair represents the real part of a complex number; the second represents the imaginary part.

Complex Mathematics Library. A C++ class library that provides the facilities to manipulate complex numbers and perform standard mathematical operations on them.

complex number. A number consisting of an ordered pair of real numbers, expressible in the form a+bi, where a and b are real numbers and i squared equals minus one. A complex number is made up of two parts: a real part and an imaginary part, where a is the value of the real part and b is the value of the imaginary part and where i is the square root of -1.

complex type. In FORTRAN, a data type that represents values of complex numbers. A value is expressed as an ordered pair of real data items separated by a comma and enclosed in parentheses. The first item represents the real part of the complex number, and the second item represents the imaginary part.

component. (1.) One part of a structured type or value, such as an array element or a record field. (2.) In AIXwindows or Enhanced X-Windows, the widget, gadget, or other graphical object that makes up an interactive user interface. (3.) In Ada language, a value that is a part of a larger value, or an object that is part of a larger object.

component bar. In an Interleaf document, the black bar at the left margin that contains the component identifiers for the components contained in that document.

component dump table. A structure used by kernel components to identify data structures that should be collected by the kernel dump program.

compose. To set type.

Compose window. In CDE, in Mailer, the window you use to create new electronic mail messages. Several message-composing options are available from the Compose window menu bar.

Composite Manager. In AIXwindows, a manager widget with special knowledge about the handling of one or more of its children widgets. Normally, a manager widget has no knowledge of its children, but a TitleBar widget and a ScrollBar widget can be registered as children of a certain type of Composite Manager widget known as a Panel widget, and the Panel widget will correctly control the positioning of the TitleBar and ScrollBar widgets.

composite type. In Ada language, a composite type is one whose values have components. There are two kinds of composite type: array types and record types.

composite video. The combined luna, chroma, and sync signals in accordance with the NTSC standards in the U.S., and the PAL standards in Europe. Also called NTSC or PAL (Europe).

composite widget. In Enhanced X-Windows, a widget that is a container for an arbitrary, implementation-defined collection of children. These children may be instantiated by the composite widget itself, by other clients, or by a combination. Composite widgets contain methods for managing the geometry (layout) of any child widget. A composite widget is a subclass of the Core widget.

Composite widget class. In Enhanced X-Windows, a metaclass that does not instantiate any widgets of its own but provides the resources and functionality that allow parent widgets to manage the layout and mapping of their children widgets and gadgets.

compound license. In License Use Management, a type of license that allows a system administrator to generate license passwords for a given number of licenses. Such a license is valuable when an administrator needs a certain number of licenses, but does not yet know what machines or who will use them. A compound license can generate either nodelocked or non-nodelocked licenses, not both.

compound object. In AIXwindows, a graphical object made up of several widgets and gadgets collected within a single container widget.

compound string. A type of string designed to simplify foreign language support by allowing text to be displayed without hard-coding the language-dependent attributes (character set, text, and direction).

compress. (1.) To move files and libraries together on disk to create one continuous area of unused space. (2.) In data communications, to delete a series of duplicate characters in a character string.

compressed output. Synonym for compression.

compression. (1.) A technique for removing strings of duplicate characters, gaps, empty fields, and trailing blanks before transmitting data. Synonymous with compressed output. (2.) In SNA, the replacement of a string of up to 64 characters by an encoded control byte to reduce the length of the data stream sent to the LU-LU session partner.

computational memory. The set of all virtual-memory pages in real memory that are part of working-storage or program-text segments.

computed time. The result of the synchronization process--the time value that the clerk or server process computes according to the values it receives from several servers.

computer aided instruction (CAI). A data processing application in which a computing system is used to assist in the instruction of students.

Computer Graphics Metafile. A device-independent graphics file format used for storing object-oriented graphics.

computer instruction. An instruction that can be recognized by the processing unit of the computer for which it is designed. Synonymous with machine instruction.

computer language. Synonym for machine language and machine instruction.

computer word. Synonym for word.

concatenate. (1.) To link together. (2.) To join two character strings.

concatenation. (1.) Linking together. (2.) Joining two character strings. (3.) In GL, combining a series of geometric transformations such as rotations, translations, and scaling. Concatenation of transformations corresponds to matrix multiplication.

concave and convex polygons. In computer graphics, a polygon is convex if a line segment joining any two points in the figure is completely contained within the figure. Nonconvex polygons are sometimes called concave. Algorithms that render only convex polygons are much simpler than those that can render both convex and concave polygons.

concentrator. An FDDI node that has additional parts beyond those required for its own attachment to a FDDI network. These additional parts (type M) are for attaching other FDDI nodes (type S) in a tree topology. Primarily, a concentrator is used to allow more than two single attachment stations (SAS) to communicate. It can also connect multiple SAS to a dual attachment station (DAS) ring.

concrete class. An OM class of which instances are permitted.

concurrent-use license. In License Use Management, a type of license administered by the license server that can be used by different users at any node that is connected to a license server node. Concurrent-use licenses allow as many users to use a software product concurrently as there are licenses.

condensed print. A print format where characters are smaller and spaced closer together horizontally, typically at a density of 17 characters per inch.

condition. An expression in a program or procedure that can be evaluated to a value of either true or false when the program or procedure is running.

condition code. Synonym for flag.

conditional. Conditionals test for certain circumstances to carry out particular commands.

conditional branch. A branch that is taken when a specified condition is met.

conditional compilation statement. A preprocessor statement that causes the preprocessor to process specified code in the file depending on how a specified condition evaluates.

conditional expression. A C language expression that contains a condition (the first expression), an expression to be evaluated if the condition has a nonzero value (the second expression), and an expression to be evaluated if the condition has the value 0 (zero).

conditional statement. (1.) A statement that runs if a specified expression evaluates to a nonzero value. (2.) A statement that permits execution of one of a number of possible operations, with or without a transfer of control. (3.) A statement used to express an assignment or branch based on specified criteria.

condition variable. A synchronization object used in conjunction with a mutex. A condition variable allows a thread to block until some event happens.

conditioning. (1.) The use of indicators to control when calculations or output operations are to be performed. (2.) In data communications, the addition of equipment to a nonswitched voice-graded channel to provide minimum values of line characteristics required for data transmission.

conduit. A pipe for protecting electrical wires or cables.

configuration. (1.) The group of machines, devices, and programs that make up a data processing system or network. (2.) The process of describing to a system the devices, optional features, and program products that have been installed so that these features can be used. Contrast with customization.

configuration feedback window. In AIXwindows, a window displayed in the center of the screen when AIXwindows Manager is restarted or when a behavior switch is requested. The window contains such variables as the size and location of a client window.

configuration file. A file that specifies the characteristics of a system or subsystem; for example, the operating system queueing system.

configuration manager. A program to supervise device configuration during initial program load (IPL).

configuration operation/procedure. Themultistep process, performed in the host computer, of constructing a configuration image for a 3601 Finance Communication Controller.

Configuration Rules Object Class. An object class that contains the configuration rules used by the configuration manager during initial program load (IPL).

configure. To describe to a system the devices, optional features, and program products installed on a system.

configure method. Takes a device from the defined state to the available state. If a device has a device driver, the configure method is responsible for loading and binding the driver into the kernel. If the device supports the optional stopped state, the configure method takes the device from the defined state to the stopped state.

confirm. In X.25 communications, to respond to the arrival of a clear-indication or reset-indication packet.

CONFIRM. A request that asks the remote transaction program to tell whether the last transmission was received successfully.

confirmation. A transmission by a receiver that permits a sender to continue.

CONFIRMED. A response to the CONFIRM request indicating that the remote site received the transmission without detecting any errors.

conformant string. In Pascal, a string whose declared length does not match that of a formal parameter. See also formal parameter.

congruence class. In a cache, the group of lines to which a given memory location can be mapped.

connect. In X.25 communications, to connect a port to the X.25 network.

connect data set to line (CDSTL). In SNA, an option that determines how the data terminal ready (DTR) signal to the modem operates. It is used if DTR indicates an unconditional command from the DTE (data terminal equipment) to the attached DCE (data circuit-terminating equipment) to connect to or remove itself from the network.

connect-time accounting. The record of the amount of time each user spends logged in to the system.

connected unit. In FORTRAN, a unit that is connected to a file by either an OPEN, READ, or WRITE statement.

connection. (1.) In SNA, the network path that links together two LUs in different nodes to provide communications channels between them for the application programs running at the respective LUs. (2.) In X.25 communications, the existence of a virtual circuit between two data terminal equipments (DTEs). A switched virtual circuit (SVC) connection is for the duration of a call; a permanent virtual circuit (PVC) connection is a permanent connection between the DTEs. (3.) In Enhanced X-Windows, the IPC path between the server and a client program. A client program typically, but not necessarily, has one connection to the server over which requests and events are sent. (4.) In system communications, a communication link over which data can be passed between two systems or between a system and a device.

connection close. All events made by the client are discarded and the server resets its state to having no connections.

connection establishment. The phase in connection mode that enables two data link service (DLS) users to create a data link connection between them.

connection identifier (CID). (1.) A value used to identify a resource. The value is returned to the connecting program after connect processing has established a session and must be used on subsequent requests to the resource. (2.) In the X.25 API, the name used to identify a call that has been made or received.

connection key. Identifies a subclass of devices that can connect to the intermediate device at the specified location.

connection location. Identifies a specific location on the intermediate device where a child device can be connected.

connection management stream. In X.25, a special stream that receives all incoming connect indications destined for DLSAP addresses that are not bound to any other streams associated with a particular PPA.

connection mode. A circuit-oriented mode of transfer in which data is passed from one user to another over an established connection in a sequenced manner.

connection-oriented protocol. A connection-based, reliable, virtual-circuit transport protocol, such as TCP; an RPC protocol that runs over a connection-based transport protocol.

connection profile. A data management file that contains parameters that associate other defined profiles to the connection of two logical units.

connection type. This is a field in the Predefined Connection Object Class. For an intermediate device, it identifies the subclass of devices that can be connected to it.

connectionless mode. A mode of transfer in which data is passed from one user to another in self-contained units with no logical relationship required among the units.

connectionless packet delivery. A method of data packet delivery that treats each packet of information individually and does not guarantee delivery.

connectivity. An algorithm that determines if two machines on different networks can communicate. If the machines can communicate, connectivity also determines which host names should be used and which TCP/IP routing information must be added.

connector. (1.) An electrical part used to join two other electrical parts. (2.) A flowchart symbol that represents a break in a flow line and indicates where the flow line is continued. (3.) A means of establishing electrical flow.

consistent. Pertaining to a file system, without internal discrepancies.

console. (1.) The main operating system display station. (2.) Synonym for system console.

console bell. Synonym for BEL.

console device. During the installation of the base operating system (BOS), the system console is the display device at the system on which you are installing the software.

console display. A display at a system console on which an operator can display, send, and reply to messages and use all control commands.

constant. A data item with a value that does not change during the running of a program. Contrast with variable. For Ada programming, see also object.

constant expression. An expression having a value that can be determined during compilation and that does not change during the running of the program.

constant folding. Performing operations in which operands are all constants at compilation time and treating the results as constants.

constant-width characters. A character set designed so each character is the same width as the other characters.

constraint. In Ada language, a constraint determines a subset of the values of a type. A value in that subset satisfies the constraint.

Constraint. In AIXwindows, a class of objects from which a unique resource set can be inherited. For example, a PanedWindow widget can specify the size of its children by using the inherited XtNmin and XtNmax Constraint resources. The reference material associated with each widget specifies those that inherit resources from the Constraint class.

constraint widget. In Enhanced X-Windows, a widget that is a subclass of a composite widget. It manages the geometry of its children based on constraints associated with each child.

constructor. A special C++ member function that has the same name as a class. It is used to construct class objects and may initialize them.

Consultative Committee on International Telegraphy and Telephone (CCITT). A United Nations Specialized Standards group whose membership includes common carriers concerned with devising and proposing recommendations for international telecommunications representing alphabets, graphics, control information, and other fundamental information interchange issues.

contact port. Synonym for well-known port.

container. In CDE, a control intended to hold objects or data. A folder and a notebook are examples of containers. In Mailer, your electronic mailbox 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.

containment. A pointer is "contained" if the pointer is located in the window, and not within an inferior of the window, and the cursor hotspot is within a visible region of a viewable window or one of its inferiors. The border of the window is considered part of the window.

contention. (1.) In a local area network, a condition on a communications channel when two or more stations are allowed by the protocol to start transmitting concurrently and thus risk collision. (2.) A condition on a session when two programs try to start a conversation at the same time.

contention scope. The group of threads against which a given thread must compete for the CPU. If local, the thread competes against other threads in the same process. If global, the thread competes against all other threads in the system.

context address. A regular expression enclosed in slashes (/).

context clause. For Ada programming, see compilation unit.

context expression. In SOM, an optional expression in a method's IDL declaration, specifying identifiers whose value (if any) can be used during SOM's method resolution process and/or by the target object as it executes the method procedure. If a context expression is specified, then a related Context parameter is required when the method is invoked. (This Context parameter is an implicit parameter in the IDL specification of the method, but it is an explicit parameter of the method's procedure.) No SOM-supplied methods require context parameters.

context line. In the Performance Toolbox, menu items ending in a slash and three dots (/...). The slash and three dots signify that the line itself represents a list at the next hierarchical level. Contrast with statistic line.

context structure. An ordered group of variables specifying the interface properties (notably location) of a shadow widget.

continuation line. A line of a source statement into which characters are entered when the source statement cannot be contained on the previous lines.

continuation reference. A continuation reference describes how the performance of all or part of an operation can be continued at a different DSA or DSAs.

continue statement. A C language control statement that contains the keyword continue and a semicolon.

control. In CDE, a generic term for a variety of elements (such as buttons, check boxes, and scroll bars) that perform an action or indicate an option setting. See Front Panel control.

control block. A storage area used by a program to hold control information.

control character. (1.) A character that is not a graphic character such as a letter, number, or punctuation mark. Such characters are called control characters because they frequently act to control a peripheral device. RETURN and FORM-FEED are control characters that control a workstation or printer. Synonymous with nonprinting character. (2.) The Ctrl key on the keyboard. (3.) A character, occurring in a particular context, that initiates, modifies, or stops any operation that affects the recording, processing, transmission, or interpretation of data (such as carriage return, font change, and end of transmission). (4.) A nonprinting character that performs formatting functions in a text file.

control commands. Commands that allow conditional or looping logic flow in shell procedures.

control state. A state that represents the current network installation management (NIM) operation being performed on a machine. This state is one of two machine states.

control key. (1.) The keyboard key labeled Ctrl. (2.) A key combination, made by pressing the Ctrl key followed by another key on the keyboard, that performs a function or makes a special character.

control path. The set of line, hardware, and control disciplines that determine the current characteristics of a particular TTY.

control point profile name. The name of the control point profile that defines the node ID of the physical unit associated with the attachment.

control points. In computer graphics, points in real space that control the shape of a spline curve. The system provides hardware support for wire frame rational cubic splines, and for NURBS surfaces, the specifications of which require four control points.

control program (CP). Part of the operating system that determines the order in which basic functions should be performed.

control statement. In programming languages, a statement that is used to alter the continuous sequential execution of statements. A control statement can be a conditional statement or an imperative statement.

control station. The primary or controlling computer on a multipoint line. The control station controls the sending and receiving of data.

control unit terminal (CUT) mode. A protocol used for communications with a 3174/3274 Controller or other appropriate interface unit. In this protocol, a program in the workstation is emulating a 3278/79 terminal for a user, and the interface unit is responsible for enforcing the protocol.

controlling terminal. This term refers to an active workstation at which a user is authorized to enter commands that affect system operation. The controlling terminal for any process normally is the active workstation from which the process group for that process was started. A workstation can have no more than one controlling process group and a process group can have no more than one controlling terminal. The controlling process group receives certain interrupt signals from the controlling terminal.

convenience creation subroutine. Creates certain useful combinations of widgets known as convenience widgets or convenience dialogs, including the appropriate Shell widgets where necessary.

convenience dialog. A widget or collection of widgets created by an AIXwindows Dialog convenience subroutine.

convenience function. A function that performs a frequently needed series of tasks automatically to create or manage widgets or other code structures. Convenience functions are included in the AIXwindows Toolkit.

convenience interface. An interface created by an AIXwindows convenience creation subroutine. See also convenience creation subroutine.

converged peripheral node. In SNA, a type of physical unit that has limited addressing and path control routing capabilities. It provides general connectivity to other SNA nodes and supports parallel sessions, multiple sessions per LU, primary and secondary LUs, and multiple lines per node.

conversation. (1.) In SNA, the logical connection between a pair of transaction programs for serially sharing a session between type 6.2 logical units from transaction to transaction. While a conversation is active, it has exclusive use of an LU-LU session as delimited by a distinct bracket; successive conversations may use the same session. (2.) An interchange of information between two application programs. (3.) A pathway between two application programs that allows them to exchange information. (4.) Interaction between a computer and a user by means of a keyboard.

conversation correlator. An internal SNA identifier used by the LU services to track which applications are using which conversations. An identifier of 1 to 8 bytes that is assigned by the attach function and maintained by LU services.

conversation key. A short-lived encryption key provided by the Authentication Service to two principals for the purpose of ensuring secure communications between them.

conversation mode. A mode of operation of a computer system in which a sequence of alternating entries and responses between a user and the system takes place in a manner similar to a dialog between two persons.

conversion. (1.) In programming languages, the transformation between values that represent the same data item but belong to different data types. (2.) A change in the type of value. For example, when you add values having different data types, the compiler converts both values to the same form before adding them. See also transaction program.

conversion code. In a print function call, a specification of the type of the value, as the value is to be printed (in octal format, for example).

conversion function. A C++ member function that specifies a conversion from its class type to another type.

conversion specification. In a print function call, a specification of how the system is to place the value of zero or more format parameters in the output stream. Each conversion specification contains a % (percent) symbol that is followed by conversion modifiers and a conversion code.

converter. A device that converts data from one form to another without altering the underlying information.

converter cache. A high-speed buffer storage that contains frequently accessed information associated with a client application. The primary purpose of a converter cache is to reduce access time to key information.

coordinate system. A given convention for locating pixels on a given display or window, where, in AIXwindows, X is the horizontal axis and Y is the vertical axis. The origin is [0,0] at the upper-left or lower-left corner, depending on the convention in use. For a window, the origin is at the upper left or lower left (depending on the convention in use), inside the border. Coordinates are discrete and specified in pixels. Each window and pixmap has its own coordinate system.

coprocessor. (1.) A supplementary processor that performs operations in conjunction with another processor. (2.) In personal computers, a microprocessor on an expansion board that extends the address range of the processor in the system unit or adds specialized instructions to handle a particular category of operations.

copy. (1.) The action by which the user makes a whole or partial duplicate of an already existing data object. (2.) Either a copy of an entry stored in other DSAs through bilateral agreement, or a locally and dynamically stored copy of an entry resulting from a request (a cache copy).

copy constructor. A C++ constructor used to make a copy of a class object from another class object of the same class type.

copy-link. A link established between a target file and the copied version of the same file. Any changes made to the copied version of the target file are automatically made to the original target file.

copy-on-write. An option that creates a mapped file with changes that are saved in the system paging space, instead of saving the changes to the copy of the file on the disk.

CORBA. In SOM, the Common Object Request Broker Architecture established by the Object Management Group. IBM's Interface Definition Language used to describe the interface for SOM classes is fully compliant with CORBA standards.

Core. In AIXwindows, Core is the top-level superclass from which all widgets and gadgets are derived. Core consists of three subclasses (Object, RectObject, and WindowObj) that collectively provide the appearance resources and behavioral resources required by all widgets and gadgets in the AIXwindows toolkit.

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

core widget. In Enhanced X-Windows, the widget that contains the definitions of fields common to all widgets. All widgets are subclasses of the core widget.

corequisite. A product or update that must be installed concurrently with another specified product or update.

correlator. A value passed between two or more programs that allows correlation or identification of mutual resources.

counter. (1.) A register or storage location used to accumulate the number of occurrences of an event. (2.) In the X.25 API, a variable that is increased by one when a packet arrives and is decreased by one when a packet is received; it can be used to notify the application program of incoming packets.

counter identifier. In the X.25 API, the name of a counter.

country code. In X.25 communications, the 3-digit number that precedes the national terminal number in the network user address (for public networks).

coupler. A device connecting a modem to a telephone network.

courier. In DTS, a local server that requests a time value from a randomly selected global server each time it synchronizes.

CP. See control program.

CPS. Characters per second.

CPU. See central processing unit.

CPU lock. See nodelocked license.

CPU time. The amount of time a program is running in the CPU or is being serviced by the operating system. Does not include time associated with the program's I/O or time in which other processes preempt the program's use of the CPU.

crash. An unexpected interruption of computer service, usually due to a serious hardware or software malfunction.

CRC. See cyclical redundancy check character.

Create Action. In CDE, a software application that enables you to associate an icon with a command so that the command can be issued by clicking on the icon. Create Action is also used to define specific data types for an application's data files and to associate icons with those data types.

creation date. The date when the file was created.

critical resource. The system resource whose speed and/or size limits the speed with which a particular workload can be processed.

critical sections. Portions of shared data to which simultaneous access by multiple threads or applications must be prevented.

cross-referencer. In Ada language, a tool that provides a listing of all places where symbols are declared, assigned to, or referenced within a compilation unit. Symbols are identified by name, class, and enclosing unit, and references to the symbol are identified by source file line numbers.

CRQ. See call request.

CRT. See cathode ray tube.

CSC. See core sequence controller.

CSMA/CD. See carrier sense multiple access with collision detection.

CSX. Host-based diagnostics program.

C-stub. The part of the DUA that implements the connection with the communications network.

CTC. Channel-to-channel.

CTS. Clear to send. Used with EIA-232 protocol.

CUD. See call user data.

CUG. See closed user group.

culling. (1.) In GL, if a primitive is smaller than the minimum size specified in the command, it is culled: no further commands in the primitive are interpreted. See also clipping, pruning. (2.) In the graPHIGS API, if a polygon is backfacing, it may be culled, or not rendered.

currency time. The time at which a user reads news items. The news command considers only the items posted after this time to be current for the user.

current. For an Ada-language compilation unit, the state where none of that unit's supporters has been recompiled since the unit itself was compiled. This implies that all of the supporters exist, since the Ada language requires this in order for the program to be compiled. Currency implies that all supporters of a unit were compiled in the correct order, as defined by Ada language rules.

current character position. The two-dimensional screen coordinates where the next character string or pixel read/write operation will occur.

current color. The color that is employed to color all subsequent drawing primitives. All drawing primitives are drawn with this color until it is changed.

current directory. The directory that is active and can be displayed with the pwd command. Relative path name resolution begins in the current directory. Synonymous with current working directory.

current file. (1.) The file being edited. If multiple windows are in use, the current file is the file containing the cursor. (2.) In the make command, the file that the make command is working with at a given moment. The make command replaces the $* macro with the name of the current file.

current folder. In CDE, the currently opened folder in an active File Manager view.

current graphics position. The homogeneous three-dimensional point from which geometric drawing commands draw. The current graphics position is not necessarily visible.

current graphics window. In GL, the window to which the system directs the output from graphics routines.

current heap. In Pascal, the area of storage where dynamic variables allocated by calls to NEW reside. Other heaps can exist at the same time, but only one is current.

current host. Synonym for local host.

current line. The line on which the cursor is located.

current record. (1.) The record pointed to by the current line pointer. (2.) The record that is currently available to the program.

current record pointer (CRP). A logical indicator used when sequentially processing SFS files or selected ranges of records from those files. The CRP tracks which of the records in the selected range has just been processed and which will be processed next.

current selection. A highlighted text block or element.

current session. In CDE, the session saved by Session Manager when you log off. At the next login, unless you specify otherwise, this session automatically opens, enabling work to continue where you left off. Contrast with home session.

current transformation matrix. The transformation matrix on top of the matrix stack. All points passed through the graphics pipeline are multiplied by the current transformation matrix before being passed on. The current transformation matrix is a concatenation of the current modeling and viewing matrices. See also transformation.

current window. The window to which the system directs the output from graphics routines. See also window.

current working directory. Synonym for current directory.

cursor. (1.) A movable symbol (such as an underline) on a display that indicates to the user where the next typed character will be placed or where the next action will be directed. (2.) In Enhanced X-Windows, the visible shape of the pointer on a screen. A cursor consists of a hotspot, a source bitmap, and a pair of colors. (3.) A primitive such as an arrowhead that can be moved about the screen by means of an input device (typically a mouse).

cursor glyph. In GL, a 16x16 or 32x32 raster pattern (bitmap that determines the shape of the cursor. A GL cursor glyph can be one or two bits deep; thus, a GL cursor can use up to three colors. Color 0 is always transparent.

cursor ID. In Enhanced X-Windows, a unique identification number that is associated with each unique type of cursor.

cursor movement keys. The directional keys used to move the cursor without altering text.

cursor stability. In file systems other than one managed by SFS, the ability to simultaneously maintain multiple contexts within a single file system. The SFS equivalent of a cursor is provided by the ability to simultaneously obtain multiple OFDs on a single file.

Customer Information Control System (CICS). A licensed program that enables transactions entered at remote workstations to be processed concurrently by user-written application programs. It includes facilities for building, using, and maintaining databases.

customization. (1.) In the NIM environment, this is optional software installation. (2.) The process of describing optional changes to defaults of a software program that is already installed on the system and configured so that it can be used. Contrast with configuration. See also system customization.

customization profile. A file containing the descriptions of optional changes to the default settings of a device or a software program.

customize. (1.) To describe to the system the devices, programs, users, and user defaults for a particular data processing system or network. (2.) To describe optional preferences or changes to defaults in a software program that is already installed and configured. Contrast with configure.

Customized Database. An entity within the ODM that contains configuration data for defined or available devices in the system. See also Device Configuration Database and Predefined Database.

Customized Devices Object Class. A representation within the ODM of each device instance as distinguished by a unique logical name. The Customized Devices Object Class contains basic information about the device such as device status and how to access the information contained in other object classes.

CUT. See control unit terminal mode.

cycle time. (1.) The time elapsed during one cycle of the processor. Cycle time varies from one type of processor to another. (2.) The minimum time interval between starts of successive read/write cycles of a storage device.

cyclic redundancy check (CRC) character. A character code used in a modified cyclic code for error sensing and correction.

cylinder. All fixed disk or diskette tracks that can be read or written without moving the disk drive or diskette drive read/write mechanism.

cylindrical coordinate system. An array where the left edge of each row is functionally adjacent to the right edge of the same row.

Cyrillic. Cyrillic alphabet. An alphabet used for writing Old Church Slavonic and for Russian and various other Slavic languages.