Glossary A

A5-relative reference

An address designated by a 16-bit offset from the A5 register in the 680x0-based Apple Macintosh. An A5-relative reference is similar to the "near data" address in Intel-based machines.

ABC width

Or ABC character spacing. 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 overhang, underhang.

abnormal termination

In exception handling, the condition that occurs when a program leaves the try block of a try-finally statement before the code executes to the closing brace. For example, statements such as return, goto, continue, and break can cause abnormal termination.

absolute position

The ordinal position of a record in a recordset. In ODBC, absolute position is one-based; in DAO, it is zero-based.

absolute symbol

A symbol that contains a constant value for an address in memory not associated with a program address.

absolute time

An expression of time that stays the same regardless of the time zone.

abstract class

Or abstract base class. In C++, a class that cannot be instantiated but is used as a base from which other classes can be derived. An abstract class contains at least one pure virtual function; if its derived classes do not implement these pure virtual functions, then they, too, become abstract classes.

abstract declarator

A declarator that does not declare a name — the identifier is left out. For example,

char *

declares the type "pointer to type char."

abstract declarator

A declarator that does not declare a name[.--]the identifier is left out. For example, in C++, [lb]char *[\lb] declares the type "pointer to type char."

accelerator key

Or keyboard accelerator, shortcut key, keyboard shortcut. A keystroke or combination of keystrokes that invokes a particular command. See also accelerator table, access key.

accelerator table

Or accelerator resource. A data structure that contains a list of accelerator keys and the command identifiers associated with them.

access control

The keywords public, private, mutable, and protected that restrict member usage of variables, member functions, and local types. Access is granted by a class. Access control is assigned to class members and does not depend on type.

access key

Or mnemonic key. The key that corresponds to an underlined letter on a menu or dialog-box item. An access key can be used to invoke the command associated with that menu item or dialog-box item. See also accelerator key.

access mode

A mode that determines the manner in which entry to a file, directory, or other data source object is permitted, as well as the manner in which changes are made to the data. See also direct mode, transacted mode.

access privileges

In object-oriented programming, the degree to which a class grants outside access to its data and functions. See also friend.

access token

A group of security attributes permanently attached to a process when a user logs on to the operating system. An access token contains privileges and security identifiers for a user, global group, or local group. The privileges regulate the use of some system services and the security identifiers regulate access to objects that are protected by access-control lists (ACLs). There are two kinds of access tokens: primary and impersonation. See also impersonation token, primary token, privilege, security identifier (SID).

access-control list

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

ACF

A special file having two parts: an interface header similar to the interface header in an IDL file, and a body that contains configuration attributes for types and functions defined in the interface body of the IDL file.

ACL

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

activation

The process of making a window or other object operational. Activation of a window, for example, changes the color of the title bar, moves the window to the top of the Z order, and enables keyboard focus. In OLE, the term "activation"  is often used to refer to in-place activation of embedded objects.

active content

Generic term for active documents, active scripts, and active objects.

active document

Generic term for documents that include active content. Examples of active documents are an HTML page, a Java applet, an OLE document-object, and a document that contains ActiveX controls.

active HTML document

A Web page that contains ActiveX controls, active scripts, or Java applets.

active HTML documents

Web pages containing ActiveX controls, script, or Java applets.

active script

Executable scripts embedded in HTML, such as JScript or VBScript.

active state

1. In OLE, the state of an OLE object in a compound document when the user can edit the embedded object without leaving the container document's window.

2. In general, the state of a program, document, device, or portion of the screen that is currently operational.

Active Template Library

A set of compact, template-based C++ classes that simplify the programming of Component Object Model objects. ATL provides the mechanism to use and create COM objects.

ActiveX

All component technologies built on Microsoft's Component Object Model (COM), other than Object Linking and Embedding.

ActiveX control

The new name for programmable elements formerly known variously as OLE Controls, OCXs, or OLE Custom Controls. Controls previously built with the MFC Control Developer's Kit meet the ActiveX control specification.

ActiveX scripting

Microsoft technology for connecting third-party script engines to applications.

ActiveX server extension

A dynamic-link library (DLL) that creates server extensions on any ISAPI-compliant Web server.

ActiveX server filter

A dynamic-link library (DLL) that intercepts and processes notifications directed to any ISAPI-compliant Web server.

ActiveX server framework

Microsoft tools for creating extensions to ISAPI-compliant Web server software. See also ActiveX server extension, ActiveX server filter, ActiveX scripting.

ActiveX Server framework

Server-side technology extensions, including ISAPI, ActiveX server controls, Active server applications, ActiveX server filters, and ActiveX server scripts.

actual argument

1. Or actual parameter. A unit of information (variable, constant, pointer, etc.) passed in a macro call or inside the parentheses of a function call that the called function then converts to its formal parameter.

2. In the Visual C++ documentation, the argument passed to a C++ template class.

actual parameter list

The arguments specified in a particular method or function call. See also formal parameter list.

address

The path to a value, object, document, page, or other destination. An address can be a memory location, a URL (address to an Internet site) or a UNC network path (address to a file on a local area network). An address may also contain more specific information such as a database object, a bookmark in a file, or a spreadsheet cell range to which the main address points.

address space

1. Or memory space. The portion of memory allocated to a given process. See also heap.

2. Or memory space. More generally, the range of memory locations to which a microprocessor can refer. Effectively, a computer's address space is the amount of memory a microprocessor could use if all the memory was available.

address-of (&) operator

In C/C++, a unary operator that gives the address of its operand, which can be either a function name or an l-value. The result of the address-of operation is a pointer to the operand. The type addressed by the pointer is the type of the operand. Note that the ampersand (&) character is also used by the bitwise-AND (&) operator. See also bitwise operator, indirection (*) operator.

ADSP

A network protocol for interprocess communication between Apple Macintosh computers and other platforms.

advise sink

An interface of a COM object that can receive notifications of changes in an embedded object or linked object. Containers that need to be notified of changes in objects implement an advise sink. Notifications originate in the server, which uses an advisory holder object to cache and manage notifications to containers. See also container application, object handler.

AFXDLL

Redistributable dynamic-link libraries (DLLs) containing the entire 32-bit Microsoft Foundation Class Library. AFXDLL enables you to build an application without statically linking to the MFC object-code libraries. The architecture is useful in building MFC extension DLLs and in sharing the class library between multiple executable files, thus saving disk space and memory.

aggregate object

In the Component Object Model, an object whose implementation of certain interfaces is provided by one or more of its contained objects.

aggregate type

Or complex type, nonscalar type. In C/C++, a structure, union, or array data type. In C++, a class can also be an aggregate type, provided it does not have constructors, nonpublic members, base classes, or virtual functions.

aggregation

A composition technique for implementing COM objects. With aggregation, a new object can reuse one or more existing objects. This reuse is achieved by exposing one or more of the interfaces in the original object.

aliasing

1. In programming, to use an alternate name to refer to a memory location that is already referred to by a different name, or to allow two pointers to point to the same memory location. The alternate name is an "alias."

2. In computer graphics, a rendering technique that assigns to pixels the color of the primitive being rendered, regardless of whether that primitive covers all or only a portion of the pixel's area. This results in a jagged, or "stairstep," appearance of certain design elements, such as diagonal lines, curves, and circles.

3. More generally, to substitute one name, or alias, for another name, or for a group of names. For example, a long Macintosh filename could be aliased with an MS-DOS 8.3-format filename.

alpha value

In mixing models, the component used to control color blending. See also red, green, blue, alpha (RGBA).

ambient property

A run-time property that is managed and exposed by the container. Typically, an ambient property represents a characteristic of a form, such as background color, that is communicated to a control so the control can assume the look and feel of its surrounding environment. See also run-time property.

ambiguity

1. In derived classes, a condition that occurs when an expression can refer to more than one data type, object, or function. Use of the scope resolution (::) operator resolves the ambiguity.

2. In syntax, a condition that can occur with a type cast, especially a function-style type cast. For example, it is unclear whether the expression char *aName( String( s ) ) is a function declaration or an object declaration with a function-style cast as the initializer.

3. More generally, two or more meanings for a single expression, which is anathema to a binary system.

ambiguous expression

1. An expression whose value depends on a particular order of evaluation where the language does not define one. For example, the values received by func( i, ++i ) depend on whether its parameters are passed from right to left or from left to right.

2. An expression that cannot be evaluated because the types used in the expression are not unique.

American National Standards Institute

An organization of American industry and business groups dedicated to the development of trade and communication standards. ANSI sets standards for C and other programming langages to eliminate variations that could cause problems in transporting a program from one type of computer system or environment to another.

American Standard Code for Information Interchange

The dominant standard for coding information on computers and related equipment. The ASCII coding scheme assigns numeric values to letters, numbers, punctuation marks, and certain other characters, enabling computers and computer programs to exchange information. See also ANSI character set, Unicode.

anchor

The HTML element that connects Web documents. Anchors either jump to another location, or are jumped to by other anchors. They are similar in function to bookmarks.

animation control

A window that displays animation in Audio Video Interleaved format.

anonymous structure

An unnamed structure variable declared within another structure. Members of an anonymous structure are accessed as if they were members in the containing structure.

anonymous union

In C++, a union without a tag or declarators. An anonymous union declares an unnamed object and cannot have member functions or private or protected members.

ANSI

An organization of American industry and business groups dedicated to the development of trade and communication standards. ANSI sets standards for C and other programming langages to eliminate variations that could cause problems in transporting a program from one type of computer system or environment to another.

ANSI C

The American National Standards Institute's 1990 version of the C language, which specifies the formal syntax and semantics of the language, the standard libraries that are included, and the way in which the compiler is to translate the program. ANSI compliance promotes portability of programs across different platforms.

ANSI character set

An 8-bit character set that contains the 7-bit ASCII standard character set as well as currency and mathematical symbols, accented characters, and other characters not normally found on the keyboard. Microsoft Windows version 3.1 and its applications use the ANSI character set internally. See also OEM character set, Unicode.

ANSI string

A string composed of characters from the ANSI character set.

apartment-model threading

A threading model that can be used only on the thread that created it. Compare free threading model, single threading model.

API

A set of routines that an application uses to request and carry out lower-level services performed by a computer’s operating system. For computers running a graphical user interface, an API manages an application's windows, icons, menus, and dialog boxes.

App Studio precompiled file

A binary version of the current resource file that is created by the Microsoft Visual C++ and used for quick loading of resources. Microsoft Visual C++ gives this file an .APS filename extension.

Apple Shared Library Manager

A library of code and resources that can be used simultaneously by more than one Macintosh application. (ASLM is not supported on the Power Macintosh.) See also stand-alone code.

applet

1. An HTML-based program that the browser temporarily downloads to a user's hard drive, where it runs when the Web page is open. Most often, "applet" refers to programs developed with Java.

2. Any small application.

AppleTalk

A simple local area network developed by Apple Computer that can be used by both Apple and non-Apple computers for communicating and sharing resources such as printers and file servers.

AppleTalk Data Stream Protocol

A network protocol for interprocess communication between Apple Macintosh computers and other platforms.

application class

The class, derived from the MFC class CWinApp, that encapsulates the initialization, running, and termination of a Windows-based application. An application must have exactly one object of an application class. See also application object.

Application Configuration File

A special file having two parts: an interface header similar to the interface header in an IDL file, and a body that contains configuration attributes for types and functions defined in the interface body of the IDL file.

application framework

Or framework. A group of C++ classes in the Microsoft Foundation Class Library that provides the essential components of an application for Windows. The application framework defines the skeleton, or framework, of an application and supplies standard user-interface implementations that can be placed onto the skeleton. See also class library.

application object

The single instance of the application class. The application object controls documents, views, frame windows, and templates, and specifies application behavior such as initialization and cleanup for every instance of the application.

application programming interface

A set of routines that an application uses to request and carry out lower-level services performed by a computer’s operating system. For computers running a graphical user interface, an API manages an application's windows, icons, menus, and dialog boxes.

application queue

In Microsoft Windows, a repository for messages awaiting processing by a particular application. As Windows removes messages from its system message queue, it dispatches the messages that contain application input to the relevant application queue. See also message loop, message queue.

Archie

A tool for finding files stored on anonymous FTP sites. You need to know the exact file name or a substring of it. See also Very Easy Rodent-Oriented Net-wide Index to Computerized Archives (Veronica).

archive

1. An object, derived from the MFC class CArchive, that provides a type-safe buffering mechanism for writing or reading serializable objects to or from a CFile object — a disk file or a memory file (perhaps representing the Clipboard). A given CArchive object either stores (writes, serializes) data or loads (reads, deserializes) data, but never both. See also serialization.

2. In general, a stored backup copy of data or a program, or the act of storing a backup copy of data or a program.

argument

A value or an expression used with an operator or passed to a subprogram (subroutine, procedure, or function). The program then carries out operations using the arguments. Synonymous with parameter.

arithmetic shift

A shift operation whose left operand is a signed quantity. In a right-shift operation, the sign bit is propagated into the bits vacated by the shift. See also logical shift.

array

An aggregate data type in which all the data items (elements) are of the same type. The elements are accessed by specifying the name of the array and a subscript (index), which represents the element's offset from the base address of the array. For example, myArray[3] represents the fourth element in the array. See also subscript ([ ]) operator.

artificial reference counting

A technique used to safeguard an object before calling a function or method that could prematurely destroy it. See also reference counting.

ASCII

The dominant standard for coding information on computers and related equipment. The ASCII coding scheme assigns numeric values to letters, numbers, punctuation marks, and certain other characters, enabling computers and computer programs to exchange information. See also ANSI character set, Unicode.

ASCII character

A character that is part of the American Standard Code for Information Interchange (ASCII). The ASCII character set is a standard 7-bit code for representing characters — letters, digits, punctuation, and control instructions — with binary values.

ASLM

A library of code and resources that can be used simultaneously by more than one Macintosh application. (ASLM is not supported on the Power Macintosh.) See also stand-alone code.

aspect ratio

The ratio of a pixel's width to height on a particular device. Information about a device's aspect ratio is used in the creation, selection, and display of fonts.

assertion

A Boolean statement in the debug version of a program that tests a condition that should, if the program is operating correctly, evaluate as true. If the condition is false, an error has occurred and the program will typically issue an error message that gives the user the option to abort the program, activate the debugger, or ignore the error.

assignment operator

An operator used to assign a value to a variable or a data structure. An example of an assignment operator is the simple assignment (=) operator, which assigns the value of its right operand to its left operand.

assignment statement

A statement that assigns a value to a variable or data structure. An assignment statement is usually composed of a destination variable, an assignment operator, and an expression to be assigned.

associativity

The order (either right to left or left to right) in which expressions are evaluated when adjacent operators have equal precedence and subexpressions are not enclosed in parentheses. For example, the expression 10 < 20 < 5 evaluates to 1 (true) because the less-than (<) relational operator has left-to-right associativity, causing the expression to be evaluated  (10 < 20) < 5.

asynchronous call

A call to a function that is executed separately so that the caller can continue processing instructions without waiting for the function to return. Contrast with synchronous call.

asynchronous moniker

A protocol for Internet-enabled applications and ActiveX controls that retains responsiveness of the user interface during file downloads. See also bind context, composite moniker.

asynchronous operation

1. Or overlapped I/O. In programming for Windows, a task that proceeds in the background, allowing the thread that requested the task to continue to perform other tasks. See also synchronous operation.

2. More generally, an operation that proceeds independently of any timing mechanism such as a clock.

asynchronous processing

In ODBC, a method of processing transactions in which the database driver returns control to an application before a function call completes; the application can continue nondatabase processing while the driver completes the function in progress. See also synchronous processing.

ATL

A set of compact, template-based C++ classes that simplify the programming of Component Object Model objects. ATL provides the mechanism to use and create COM objects.

atomic operation

An operation that never has its execution suspended while partially completed. See also synchronous operation.

attribute

Any keyword of the Interface Definition Language that describes a property, method, or remote procedure call.

audio-video interleaved

A Microsoft technology for displaying full-motion video in a window. An AVI file interleaves waveform audio and video data and has a .AVI filename extension.

authentication

The process of determining the identity of a user attempting to access a system. Note that the user can be a person, a computer, or a process.

authentication token

A portable device used for authenticating a user. Authentication tokens operate by challenge/response, time-based code sequences, or other techniques.

automatic object

Objects that are local to each invocation of a block. See also automatic variable.

automatic storage class

Or auto storage class. In C++, the storage class for objects and variables that are local to the block of code where they are declared. The automatic storage class can be declared explicitly, by using the keywords auto or register, or implicitly, by default. See also local variable, static storage class.

automation client

In OLE Automation, an application that can manipulate exposed objects belonging to another application (called the OLE Automation server). The client drives the server application by accessing the objects' properties and functions. Microsoft Visual Basic is an example of an OLE Automation client application. See also automation server.

AVI

A Microsoft technology for displaying full-motion video in a window. An AVI file interleaves waveform audio and video data and has a .AVI filename extension.