Glossary - C

 C    

 cached micro presentation space - A presentation space from a 
    Presentation Manager owned store of micro presentation spaces. It can 
    be used for drawing to a window only, and must be returned to the 
    store when the task is complete. 

 CDB - Command Descriptor Block. 

 cell - See character cell. 

 character box -  (1) An imaginary parallelogram on a display surface that 
    contains all parts of one graphic character. Synonymous with bounding 
    box. (T)   (2) The maximum area in which a symbol and all associated 
    elements, such as a cursor, an underline, or space surrounding the 
    symbol to separate it from other symbols, can be printed or displayed. 
    Synonymous with character cell. (3) The imaginary parallelogram whose 
    boundaries govern the size, orientation, and spacing of individual 
    characters to be displayed on a graphics display device. 

 character cell -  (1) An addressable location on a display surface or 
    printing medium.   (2) The physical width and height in pels of a 
    font. See also bounding box.   (3) The imaginary box whose boundaries 
    govern the size, orientation, and spacing of individual characters to 
    be displayed on a workstation. 

 character mode - A mode that, in conjunction with the font type, 
    determines the extent to which graphics characters are affected by the 
    character box, shear, and angle attributes. 

 clipping - In computer graphics, removing those parts of display elements 
    that lie outside of given boundary. 

 clip limits - The area of the paper that can be reached by a printer or 
    plotter. 

 clipping path - A clipping boundary in world-coordinate space. 

 code page - 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, assignment of 
    characters and meanings to 128 code points for a 7-bit code. 

 code point - A 1-byte code representing one of 256 potential characters. 

 code segment - An executable section of programming code within a load 
    module. 

 color conversion - Changing one color format to another. Required, for 
    example, when the source color format is different from the 
    destination color format. When going from the monochrome color format 
    to the color format, 1 (one) bits are converted to the image 
    foreground color, and 0 (zero) bits are converted to the image 
    background color. 

    When going from color to monochrome, all pels that match the passed 
    background color are converted to the image background color of the 
    destination. 

    All other pels are converted to the image foreground color of the 
    destination. The color conversion takes place prior to any mix mode. 

 color dithering - See dithering. 

 command code - In this specification, refers to a group of related 
    commands that an adapter device driver can receive. 

    All command codes have a prefix of "IOCC_". For example, common I/O 
    requests (such as Read, Write, etc.) are grouped under the command 
    code IOCC_EXECUTE_IO. 

 command data block - A data structure defined by the Small Computer 
    System Interface standard to send commands to devices that conform to 
    SCSI standards. 

 command descriptor block (CDB) - The structure used to communicate 
    commands from a source to a destination. 

 command modifier - In this specification, a specific operation that an 
    adapter device driver is to perform. 

    All command modifiers have a prefix of "IOCM_". For example, an 
    adapter device driver might receive an IOCC_EXECUTE_IO command with a 
    command modifier of IOCM_READ. 

 compatibility kernel - The portion of the OS/2 kernel that exists to 
    support DOS INT 20, 21, 25, 26, and 27 functions. It acts as an 
    interface to common kernel functionality such as the file system. 

 CON - Character-device name reserved for the console keyboard and screen. 
    

 conditional compilation - Processing by the preprocessor of certain 
    specified code in the file, depending on the evaluation of a specified 
    condition. 

 context hook - Similar to a "force flag" in earlier versions of OS/2. 
    These are events, signaled by a virtual device driver, that are 
    processed at task time. Forcing an IRET, and simulating an NMI, can 
    fall into this category. 

 control program - A computer program designed to schedule and to 
    supervise the execution of programs of a computer system. 

 controller sector buffer - One or more buffers, managed by a hardware 
    adapter, to improve I/O transfer rates by helping to match a device 
    and software timing requirements.