A

ABC width

The amount of spacing required for a single glyph in a font. "A" spacing is added to the current position before drawing the glyph. "B" spacing is the width of the black part of the glyph. "C" spacing is added to the current position to account for the white space to the right of the glyph. The total advanced width is given by A+B+C. See also glyph.

absolute security descriptor

A security descriptor structure that contains pointers to the security information associated with an object. See also security descriptor, self-relative security descriptor.

accelerator table

An array of ACCEL data structures, each of which defines a keyboard accelerator. See also keyboard accelerator.

access-control entry (ACE)

An entry in an access-control list (ACL). An ACE contains a set of access rights and a security identifier (SID) that identifies a trustee for whom the rights are allowed, denied, or audited. See also access-control list (ACL), security identifier (SID), trustee.

access-control list (ACL)

A list of security protections that applies to an object. (An object can be a file, process, event, or anything else having a security descriptor.) An entry in an access-control list (ACL) is an access-control entry (ACE). There are two types of access-control list: discretionary and system. See also access-control entry (ACE), discretionary access-control list (DACL), security descriptor, system access-control list (SACL).

access mask

A 32-bit value that specifies the rights that are allowed or denied in an access-control entry (ACE). An access mask is also used to request access rights when an object is opened. See also access-control entry (ACE).

access time

The last time a file was written to, read from, or run, if the file is executable.

access token

An access token contains the security information for a logon session. The system creates an access token when a user logs on, and every process executed on behalf of the user has a copy of the token. The token identifies the user, the user's groups, and the user's privileges. The system uses the token to control access to securable objects and to control the ability of the user to perform various system-related operations on the local computer. There are two kinds of access token: primary and impersonation. See also impersonation token, primary token, privilege, process, security identifier (SID).

ACE

See access-control entry (ACE).

ACL

See access-control list (ACL).

active screen buffer

The screen buffer that is currently displayed in a console's window.

active window

A top-level window of the application with which the user is working. Windows identifies the active window by positioning it at the top of the Z order and highlighting its title bar and border. See also window.

Adaptive Differential Pulse Code Modulation (ADPCM)

An audio-compression technique.

Additive color mixing

A method of color mixing that uses black as the base color to which other colors may be added. The image is black if no other colors are present. If you add red, the image will appear red. If you then add blue, the image will appear magenta. The mixing methods most commonly used are based on the additive primary colors and the subtractive primary colors. All colors can be reproduced using either method.

additive color technology

The color technology, used by video displays, that is based on the three primary colors red, green, and blue (RGB). Other colors (except black) are a combination of two or more of the primaries in varying amounts. Black is defined as the absence of the primaries.

ADPCM

See Adaptive Differential Pulse Code Modulation (ADPCM).

alertable wait

(1) A wait operation initiated when a thread calls either the WaitForSingleObjectEx, WaitForMultipleObjectsEx, or SleepEx function with the function's fAlertable flag set to TRUE. In an alertable wait, the wait function returns when a ReadFileEx or WriteFileEx function completion routine is queued for execution.

(2) A wait function operation in which the function can return when the specified conditions are satisfied, or when the system queues a completion routine for execution by the waiting thread. See also completion routine, wait function.

alternate path

One of the multiple storage shares that a junction point references in a Distributed File System (Dfs) tree structure. Dfs has a limit of 32 alternate paths for a junction point in a Dfs tree. See also Distributed File System (Dfs), junction point

animation

The display of a series of graphic images that simulates motion. Animation can be frame based or cast based.

anonymous pipe

An unnamed, one-way pipe that transfers data between a parent and child process, or between two child processes of the same parent process. An anonymous pipe is created by the CreatePipe function that returns two handles (one to the read end and one to the write end of the pipe). The creating parent process controls whether these handles are inherited by its child processes. See also child process, handle, parent process, pipe.

application-defined control

A control belonging to a window class supplied by an application.

application-defined resource

A resource whose format is defined and recognized by a specific application. See also custom resource.

association

The process of matching a filename extension with a specific application. When an extension and an application have been associated, applications can use the association to find and start other applications or to open and print files.

asynchronous input and output (I/O)

A type of I/O in which some file I/O functions return immediately, even though an I/O request is still pending. This enables an application to continue with other processing and wait for the I/O to finish at a later time. See also overlapped input and output (I/O).

asynchronous procedure call (APC)

A function that executes asynchronously in the context of a particular thread. When an APC is queued to a thread, the system issues a software interrupt. The next time the thread is scheduled, it will run the APC. APCs made by the system are called "kernel-mode APCs." APCs made by an application are called "user-mode APCs." A thread must be in an alertable state to run a user-mode APC.

asynchronous task handle

The handle returned by the WSAAsyncGetXByY routines. This handle is used to identify the outstanding operation and allow the application to cancel it if needed.

atom

An integer that identifies a character string in an atom table.

atom name

The character string identified by an atom.

atom table

A table, defined by the operating system, that stores character strings and their associated atoms. A global atom table is available to all applications. A local atom table can be used only by the application that created it.

attribute

A characteristic of a file. The six Windows file attributes indicate whether a file is read only, hidden, system, archived, a directory, or normal. See also directory.

auto-reset event object

See event object.

auxiliary audio device

Audio devices whose output is mixed with the Musical Instrument Digital Interface (MIDI) and waveform output devices in a multimedia computer. An example of an auxiliary audio device is the compact disc audio output from a CD-drive.