C

caret: A flashing line, block, or bitmap that marks the location of the insertion point in a window's client area. See also bitmap.
CD-ROM extended architecture (CD-XA): An extension of the CD-ROM standard that provides for storage of compressed audio data along with other data on a compact disc. This standard also defines the way data is read from a disc. Audio signals are combined with text and graphic data on a single track so they can be read at virtually the same time.
channel: A method, provided by Musical Instrument Digital Interface (MIDI), for sending messages to an individual device within a MIDI setup. There are 16 MIDI channel numbers. Devices in a MIDI setup can be directed to respond only to messages marked with a channel number specific to the device.
channel map: A channel map, provided by the MIDI Mapper, that can redirect Musical Instrument Digital Interface (MIDI) messages from one channel to another. See also MIDI Mapper, Musical Instrument Digital Interface (MIDI).
character code: A numeric value that represents a particular character in a set, such as the ASCII character set. See also code page.
character set: A mapping of characters to their identifying numeric values. See also multibyte character set, single-byte character set, Unicode.
character-mode application: An application that does not provide its own graphical user interface (GUI). The Win32 API provides consoles for managing input and output (I/O) for character-mode applications. See also console.
check box: A square box operated by the user to choose from a set of related but independent options. A checked check box contains an X. Repeatedly checking a check box toggles it from state to state. A standard check box has two states: checked and unchecked. A three-state check box has an additional state: disabled (grayed). In versions of standard and three-state check boxes, Windows is responsible for changing the state of the check box.
child process: A process (child) initiated by another process (the parent). The child process can operate independently from the parent process. Further, the parent process can suspend or terminate without affecting the child process. See also parent process.
child window: A window that has the WS_CHILD style. A child window always appears within the client area of its parent window.
child-window identifier: An application-defined value assigned to a child window. An application that creates multiple child windows of the same class uses the identifiers to distinguish among the child windows.
chord: A region bounded by the intersection of an ellipse and a secant. In Windows, a chord is outlined by using the current pen and filled by using the current brush. See also ellipse, secant.
chunk: The basic building block of a Resource Interchange File Format (RIFF) file, consisting of an identifier (called a chunk identifier), a chunk-size variable, and a chunk data area of variable size.
class cursor: The default cursor for a window class. The class cursor is specified by the hCursor member of a WNDCLASS structure. See also cursor.
class icon: The default icon for a window class. The class icon is identified by the hIcon member of a WNDCLASS structure. See also icon.
class menu: The default menu for a window class. All windows of a given class use the same menu unless the application specifies a different menu when creating a window of that class. See also menu, window.
click: To press and release a mouse button.
client area: The part of a window where the application displays output such as text or graphics.
client coordinates: Coordinates relative to the upper left corner of a window's client area.
clipboard: A set of functions and messages used to transfer information between applications or within an application.
clipboard format: The format of data on the clipboard. A window can copy information to the clipboard using multiple clipboard formats. A clipboard format is identified by a unique unsigned integer value. See also clipboard, window.
clipboard owner: The window associated with the information on the clipboard. It is possible for there to be no clipboard owner. See also clipboard, window.
clipboard viewer: A window that displays the contents of the clipboard. See also clipboard, window.
clip path: One or more irregular shapes in a window's client area where clipped output appears. The edges of a clip path can be straight lines, Bezier curves, or combinations of the two. See also irregular shape.
clipping: The process of limiting output to a region or path within the client area of an application's window.
clipping region: A polygon or ellipse in a window's client area where clipped output appears. See also ellipse, polygon.
CMY format: See cyan, magenta, yellow (CMY) format.
code page: A mapping of characters to 256 8-bit character codes. See also character code.
coherent: A description of file views that contain identical data at a given time. File views are coherent if they are derived from the same file-mapping object.
Color common dialog box: A common dialog box that displays available colors and controls that let the user define a custom color. See also common dialog box.
color management: A technology that translates the colors of an object (images, graphics, or text) from their current color space to the color space of output devices such as monitors, printers, and plotters.
color palette: An array containing the RGB (red, green, blue) values identifying the colors that can currently be displayed or drawn on the output device. Color palettes are used by devices that are capable of generating many colors but can only display or draw a subset of these at any given time.
color palette index: An integer value that identifies a specific palette entry.
color plane: An array of bits that represents the red, green, blue, or intensity components for the pixels in a bitmapped image. See also bitmapped image, pixel.
color space: A model for representing color as three or more coordinates. Color-space models map color components onto a Cartesian coordinate system in three or more dimensions. A color space may use any of several types of color encoding and visualizing color. The two most common types of color space models are RGB and YUV.
color table: An array of RGBQUAD structures. Each RGBQUAD structure describes a color consisting of relative intensities of red, green, and blue.
command item: A menu item that, when chosen, sends a command message to the window procedure of the window that owns the menu. See also menu item, window.
command message: In Media Control Interface (MCI), a symbolic constant that represents a unique command for an MCI device. Command messages have associated data structures that provide information a device requires to carry out a request.
command string: In Media Control Interface (MCI), a null-terminated character string that represents a command for an MCI device. The text string contains all the information that an MCI device needs to carry out a request. MCI parses the text string and translates it into an equivalent command message and data structure that it then sends to an MCI device driver.
comment: A string of text inserted between records in a metafile. See also metafile.
committed page: A page of memory in a process's virtual address space for which physical storage has been allocated. The storage is either in RAM or on disk.
common dialog box: A dialog box that an application displays by calling a single function rather than by creating a dialog box procedure and a resource file containing the dialog box template. See also resource file.
common display context: The default display context assigned to a window that does not specify CS_OWNDC or CS_CLASSDC as the window's class style. See also display context, window.
communications resource: A physical or logical device that provides a single bidirectional, asynchronous data stream. Serial ports, parallel ports, fax machines, and modems are examples of communications resources. For each communications resource, there is a service provider, consisting of a library or driver, that enables applications to access the resource.
compact disc – digital audio (CD-DA): An optical data-storage format that provides for the storage of up to 73 minutes of high-quality digital-audio data on a compact disc. Also known as Red Book audio.
compact disc – read-only memory (CD-ROM): An optical data-storage technology that allows large quantities of data to be stored on a compact disc.
compatible device context (DC): A virtual-device context that provides a means of storing an image that was created on a physical screen. (Compatible DCs are sometimes referred to as "memory" DCs.) See also device context.
completion routine: A function specified in a call to either the ReadFileEx or WriteFileEx function. A completion routine is queued for execution when the read or write operation is finished. The completion routine is not executed until the thread that called the ReadFileEx and WriteFileEx function enters an alertable wait. See also alertable wait.
composite character: An accented character represented by two character values, one for the base character and another for the nonspacing accent character. See also base character, nonspacing character, precomposed character.
compound device: A Media Control Interface (MCI) device that requires a device element, usually a data file. An example of a compound device is the MCI waveform audio driver. See also device element.
compound file: A number of individual files bound together in one physical file. Each individual file in a compound file can be accessed as if it were a single physical file.
console: An interface that provides input and output to character-mode applications. See also character-mode application.
console modes: Settings associated with a console that determine the behavior of some of its input and output operations.
console process: A character-mode process whose entry point is the main function. A console process uses the console functions or the file input and output (I/O) functions for I/O, while a graphical user interface (GUI) process uses the USER/graphic device interface (GDI) functions. See also process.
console window: A window managed by the system that a console uses to receive input and display output.
container: A network resource that contains other network resources. The contained resources can be such objects as servers or printers, or containers that can also contain further objects and containers. See also sharepoint.
context record: A record of the machine state created when an exception occurs. The context record is saved in a CONTEXT structure.
control: A child window used in conjunction with another window to carry out simple input and output (I/O) tasks.
control change: See MIDI control-change message.
control identifier: A number that an application uses to uniquely identify a control.
control message: A message sent to a control to request information or perform an action.
control set: A set of configurable options for a computer. See also profile.
control style: A value, similar to a window style, that specifies the appearance and behavior of a control. The window procedure for the control uses the style to determine how to draw the control and process input.
coordinate space: A planar space based on the Cartesian coordinate system. This system requires two axes that are perpendicular and equal in length. There are four coordinate spaces in Windows: world, page, device, and physical device (client area, or desktop, or page of printer paper).
Coordinated Universal Time: The standard international time used internally by Windows NT.
cosmetic pen: A pen with dimensions specified in device units. See also pen.
counter: A general term referring to an incrementing variable.
critical section: An object used to synchronize the threads of a single process. Only one thread at a time can own a critical-section object.
current directory: The directory at the end of the active path. This is the directory where the active application started, unless explicitly changed. See also directory.
current position: The starting point for any line-drawing or curve-drawing operations.
current selection: The portion of a document the user has marked in preparation for carrying out a command.
cursor: A small bitmap whose location on the screen is controlled by a pointing device, such as a mouse, pen, or trackball. See also bitmap.
cursor handle: A unique value of the HCURSOR type that identifies a cursor.
custom cursor: A cursor designed for use in a specific application.
custom icon: An icon designed for use in a specific application. See also icon.
custom resource: See application-defined resource.
cyan, magenta, yellow (CMY) format: A color format that identifies a given color with a cyan, magenta, yellow (CMY) format triplet. This format is used by printers and other ink-based devices.