C
call
  To transfer control to a procedure, program, routine, or subroutine. IBM.
caller
  A routine that calls another routine.
canvas
  A window with a layout algorithm that manages child windows. In IBM Open Class, the canvas classes are a set of window classes that enable you to implement dialog boxes. These dialog boxes are used for showing views of objects as both pages in a notebook and as windows that gather information to run an action. The different canvases can manage the size and position of child windows, provide moveable split bars between windows, and support the ability to scroll a window. Canvases include the base class, ICanvas, and its four derived classes: IMultiCellCanvas, ISetCanvas, ISplitCanvas, and IViewport.
carriage-return character
  A character that in the output stream indicates that printing should start at the beginning of the same physical line in which the carriage-return character occurred. The carriage-return is the character designated by '\r' in the C and C++ languages. It is unspecified whether this character is the exact sequence transmitted to an output device by the system to accomplish the movement to the beginning of the line. X/Open.
case clause
  In a switch statement, a case label followed by any number of statements.
case label
  The word case followed by a constant expression and a colon. When the selector evaluates the value of the constant expression, the statements following the label are processed.
cast
  A notation used to express the conversion of one type to another. It can be expressed using either functional notation or cast notation.
cast expression
  An expression that explicitly converts its operand to a specified arithmetic, scalar, or class type.
cast operator
  An operator used for specific type conversions.
catch block
  A block associated with a try block that receives control when a C++ exception matching its argument is thrown.
CD-XA
  See compact disc-extended architecture.
CECP
  See country extended code page.
channel mapping
  The translation of a MIDI channel number for a sending device to an appropriate channel for a receiving device.
character
  (1) A letter, digit, or other symbol that is used to represent data. (2) A sequence of one or more bytes representing a single graphic symbol or control code. This term corresponds to the ISO C standard term multibyte character, where a single-byte character is a special case of the multibyte character. Unlike the usage in the ISO C standard, character here has no necessary relationship with storage space, and byte is used when storage space is discussed. X/Open, I. See multibyte character.
character array
  An array of type char. X/Open.
character class
  A named set of characters sharing an attribute associated with the name of the class. The classes and the characters that they contain are dependent on the value of the LC_CTYPE category in the current locale. X/Open.
character constant
  A character or an escape sequence enclosed in apostrophes.
character set
  (1) A finite set of different characters that is complete for a given purpose; for example, the character set in ISO Standard 646, 7-bit Coded Character Set for Information Processing Interchange. T. See single-byte character set, double-byte character set, portable character set. (2) All the valid characters for a programming language or for a computer system. IBM. (3) A group of characters used for a specific reason; for example, the set of characters a printer can print. IBM.
character string
  A contiguous sequence of characters terminated by and including the first null byte. X/Open.
character variable
  The name of a character data item whose value is assigned or changed during program execution. IBM.
checkpoint
  (1) A sequence of instructions in a computer program for recording the status of execution for restarting. T. (2) A point at which information about the status of a job and the system can be recorded so that the job step can be later restarted. IBM.
child class
  See derived class.
child node
  A node that is subordinate to another node in a tree structure. Only the root node of a tree is not a child. See parent node, root.
child window
  A window derived from another window and drawn relative to it. See parent window.
circular slider control
  A 360-degree knob-like control that simulates the rotating knobs on a TV or a stereo. By rotating the slider arm, the user can set, display, or modify a value, such as the volume, balance, bass, or treble.
class
  (1) A group of objects that share a common definition and that therefore share common properties, operations, and behavior. (2) A C++ aggregate that may contain functions, types, and user-defined operators in addition to data. Classes can be defined hierarchically, allowing one class to be an expansion of another, and classes can restrict access to their members.
class hierarchy
  A tree-like structure showing relationships among classes that result from single inheritance. It places one abstract class at the top (a base class) and one or more layers of derived classes below it.
class key
  Any of these three C++ keywords: class, struct, or union.
class library
  In object-oriented languages, a collection of classes.
class name
  A unique identifier of a class type that becomes a reserved word within its scope.
class scope
  The scope of class member names.
class tag
  See class name.
class template
  A blueprint describing how a set of related classes can be constructed.
C library
  A system library that contains common C language subroutines for file access, string operators, character operations, memory allocation, and other functions. IBM.
C++ library
  A system library that contains common C++ language subroutines for file access, memory allocation, and other functions. See class library.
client area window
  In the IBM Open Class Library, an intermediate window between an IFrameWindow and other child windows.
client code
  A C++ program that uses a class. The program is said to be a client of the class.
CLSID
  Class identifier.
coded character set
  (1) A set of graphic characters and their code point assignments. The set may contain fewer characters than the total number of possible characters: some code points may be unassigned. IBM. (2) A coded set whose elements are single characters; for example, all characters of an alphabet. T.
code page
  (1) An assignment of graphic characters and control function meanings to all code points; for example, assignment of characters and meanings to 256 code points for an 8-bit code, or assignment of characters and meanings to 128 code points for a 7-bit code. (2) A particular assignment of hexadecimal identifiers to graphic characters.
code point
  (1) A 1-byte code representing 1 of 256 possible characters. (2) An identifier in an alert description that represents a short unit of text. The code point is replaced with the text by an alert display program.
collating element
  The smallest entity used to determine the logical ordering of character or wide-character strings. A collating element consists of either a single character, or two or more characters collating as a single entity. The value of the LC_COLLATE category in the current locale determines the current set of collating elements. X/Open.
collating sequence
  (1) A specified arrangement used in sequencing. I, ANSI. (2) An ordering assigned to a set of items, such that any two sets in that assigned order can be collated. ANSI. (3) The relative ordering of collating elements as determined by the setting of the LC_COLLATE category in the current locale. The character order, as defined for the LC_COLLATE category in the current locale, defines the relative order of all collating elements, such that each element occupies a unique position in the order. This is the order used in ranges of characters and collating elements in regular expressions and pattern matching. In addition, the definition of the collating weights of characters and collating elements uses collating elements to represent their respective positions within the collation sequence.
collation
  The logical ordering of character or wide-character strings according to defined precedence rules. These rules identify a collation sequence between the collating elements, and such additional rules that can be used to order strings consisting of multiple collating elements. X/Open.
collection
  (1) An implementation of an abstract data type for storing elements. (2) An abstract class without any ordering, element properties, or key properties. In the Collection Class Library, all abstract classes are derived from the class called Collection.
Collection Class Library
  A set of classes that provide basic functions for collections, and can be used as base classes.
Collection classes
  A set of classes that implement abstract data types for storing elements.
comma expression
  An expression that contains two operands separated by a comma. Although the compiler evaluates both operands, the value of the expression is the value of the right operand. If the left operand produces a value, the compiler discards this value. Typically, the left operand of a comma expression is used to produce side-effects.
command
  An instruction to perform an operation or run a program. When parameters, arguments, flags, or other operands are associated with a command, the resulting character string is a single command.
command line interface
  A type of computer interface in which the input command is a string of text. Contrast with graphical user interface (GUI).
common controls
  In the Windows operating system, a DLL that includes the following: header control (a window for displaying multiple columns of data), list view (a way to display objects as icons with labels), progress bar, property sheet, status bar, tool bar, track bar (slider control), tree view (an outline-type list), and an up-down control (spin control).
compact disc-extended architecture (CD-EX)
  A storage format that accommodates interleaved storage of audio, video, and standard file system data.
compact disc-read-only memory (CD-ROM)
  High-capacity, read-only memory in the form of an optically read compact disc.
compilation unit
  (1) A portion of a computer program sufficiently complete to be compiled correctly. IBM. (2) A single compiled file and all its associated include files. (3) An independently compilable sequence of high-level language statements. Each high-level language product has its own rules for what makes up a compilation unit.
compile
  To translate from source code into an object form.
compiler listing
  See listing.
compiler options
  Keywords that can be specified to control certain aspects of compilation.
complete class name
  The complete qualification of a nested class name, including all enclosing class names.
Complex Mathematics library
  A C++ class library that provides the facilities to manipulate complex numbers and perform standard mathematical operations on them.
composite
  The combination of two or more film, video, or electronic images into a single frame or display.
computer-controlled device
  An external video source device with frame-stepping capability, usually a videodisc player, whose output can be controlled by the multimedia subsystem.
concrete class
  A class that implements an abstract data type but does not allow polymorphism. See polymorphism, reference class. Contrast with abstract class.
condition
  (1) A relational expression that can be evaluated to a value of either true or false. IBM. (2) An exception that has been enabled, or recognized, by the language environment and thus is eligible to activate user and language condition handlers. Any alteration to the normal programmed flow of an application. Conditions can be detected by the hardware or operating system and result in an interrupt. They can also be detected by language-specific generated code or language library code.
conditional compilation directive
  A preprocessor directive that causes the preprocessor to process specified source code in the file depending on the evaluation of a specific condition.
conditional expression
  A compound 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 zero (the third expression).
const
  (1) An attribute of a data object that declares that the object cannot be changed. (2) An attribute of a function that declares that the function will not modify data members of its class.
constant
  (1) In programming languages, a language object that takes only one specific value. I. (2) A data item with a value that does not change during the running of the program.
constant expression
  An expression having a value that can be determined during compilation and that does not change during the running of the program. IBM.
constructor
  In C++, a special class member function that has the same name as the class and is used to construct and, possibly, initialize objects of its class type. A return type is not specified. See default constructor and destructor.
containment function
  A function that determines whether a collection contains a given element.
control
  A graphic object that represents operations or properties of other objects. See tree control.
control character
  (1) A character whose occurrence in a particular context specifies a control function. T. (2) A character, other than a graphic character, that affects the recording, processing, transmission, or interpretation of text. X/Open. See nonprinting character.
control statement
  A language statement that changes the normal path of execution.
conversion
  (1) In programming languages, the transformation between values that represent the same data item but belong to different data types. Information may be lost because of conversion since accuracy of data representation varies among different data types. I. (2) The process of changing from one method of data processing to another or from one data processing system to another. IBM. (3) The process of changing from one form of representation to another; for example, changing from decimal representation to binary representation. IBM. (4) A change in the type of a value; for example, when you add values having different data types, the compiler converts both values to a common form before adding the values.
conversion function
  A member function that specifies a conversion from its class type to another type.
Coordinated Universal Time (UTC)
  The international standard of time, kept by atomic clocks around the world.
copy constructor
  A constructor used to make a copy of an object from another object of the same type.
country extended code page
  A single-byte EBCDIC coded character set in the IBM corporate registry. Each code page contains the same character set, with an identifier of 00697 (also known as Latin Alphabet Number 1), but pages differ in their code point allocations.
critical section
  (1) Code that must be executed by one thread while all other threads in the process are suspended. (2) In the Windows operating system, a synchronization object. A critical section is not a kernel object; that is, it is not managed by the low-level components of the operating system and is not manipulated using handles. (3) A small section of code that requires exclusive access to some shared data before the code can execute. Critical threads synchronize threads only within a single process, and they allow only one thread at a time to gain access to a region of data. See mutex, semaphore, and event. Contrast with kernel object.
C/2
  A version of the C language designed for the OS/2 environment.
current working directory
  (1) A directory, associated with a process, that is used in path-name resolution for path names that do not begin with a slash. X/Open, I. (2) In DOS, the directory that is searched when a file name is entered with no indication of the directory that lists the file name. DOS assumes that the current directory is the root directory unless a path to another directory is specified. IBM. (3) In the OS/2 operating system, the first directory in which the operating system looks for programs and files and stores temporary files and output. IBM. (4) In the AIX operating system, a directory that is active and that can be displayed. Relative path name resolution begins in the current directory. IBM.
cursor
  A reference to an element at a specific position in a data structure.
cursored emphasis
  When the selection cursor is on a choice, that choice has cursored emphasis.
cursor iteration
  The process of repeatedly moving the cursor to the next element in a collection until some condition is satisfied.