Glossary

A

ActiveX All component technologies built on Microsoft's COM, other than OLE technology.

ActiveX control An embeddable, reusable COM object that supports, at a minimum, the IOleControl interface. ActiveX controls are typically created for the user interface, but they also support communication with a control container. Multiple clients can reuse these controls, depending upon licensing restrictions.

ActiveX control container An application that supports the embedding of controls by implementing the IOleControlSite interface. See also control.

ActiveX Template Library (ATL) A set of compact, template-based C++ classes that simplify the programming of COM objects. ATL provides the mechanism to use and create COM objects.

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.

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.

apartment-model threading A threading model that can be used only on the thread that created it. See also free threading model, single threading model.

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

application framework Or framework. A group of C++ classes in the MFC Library that provides the essential components of a Windows application. The application framework defines the basic operational structure of an application, and supplies standard user-interface implementations that can be incorporated into the application.

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

asynchronous operation In programming for Windows, a task that proceeds in the background, allowing the thread that requested the task to continue to perform other tasks.

ATL See ActiveX Template Library.

Automation A technology based on COM, which enables interoperability among ActiveX components, including OLE components. Formerly referred to as OLE Automation.

B

backward compatibility 1. Ensuring that existing applications will continue to work in a new environment. 2. Ensuring that the new release of an application will be able to handle files created by a previous version of a product.

bitmap Also referred to as a pixel image or pixel map. An array of bits that contains data describing the colors found in a rectangular region on the screen (or the rectangular region found on a page of printed paper).

browser A program used to view formatted Web documents.

C

call stack An ordered list of functions that have been called, but have not returned, with the currently executing function listed first. Each call is optionally shown with the arguments and types passed to it. During a debug session, you can view the functions that have been called, but have not returned.

CGI See Common Gateway Interface.

child window A window that has the WS_CHILD or WS_CHILDWINDOW style, and is confined to the client area of its parent window, which initiates and defines the child window. Typically, an application uses child windows to divide the client area of a parent window into functional areas.

class factory An object that creates one or more instances of an object identified by a given CLSID. A class factory object implements the IClassFactory interface. A class factory is one of the most frequently used types of class objects in COM.

client An application or process that requests a service from an in-process server or another process.

client area Or client rectangle. The portion of a window where an application displays output, such as text or graphics.

clipboard An area of storage, or buffer, where data objects or their references are placed when a user carries out a cut or copy operation.

CLSID A universally unique identifier (UUID) that identifies a type of COM object. Each type of COM object has its CLSID in the registry so that other applications can load and program the CLSID. For example, a spreadsheet might create worksheet items, chart items, and macro-sheet items. Each of these item types has its own CLSID that uniquely identifies the item type to the system.

collection class In object-oriented programming, a class that can hold and process groups of class objects or groups of standard types. A collection class is characterized by its shape (the way the objects are organized and stored) and by the types of its elements. MFC provides three basic collection shapes: lists, arrays, and maps (also known as dictionaries).

COM See Component Object Model.

command message In Windows, a notification message from a user-interface object, such as a menu, toolbar button, or accelerator key.

Common Gateway Interface (CGI) A mechanism that allows a Web server to run a program or script on the server and send the output to a Web browser. See also ISAPI.

Component Object Model (COM) An open architecture for cross-platform development of client/server applications based on object-oriented technology as agreed upon by Digital Equipment Corporation and Microsoft Corporation. COM defines an interface similar to an abstract base class, IUnknown , from which all COM-compatible classes are derived.

compound document Or container document. A document within a container application that contains data of different formats, such as sound clips, spreadsheets, text, and bitmaps.

connection point In OLE, a mechanism consisting of the object calling the interface, referred to as the source, and the object implementing the interface, referred to as the sink. The connection point implements an outgoing interface that can initiate actions, such as firing events and change notifications, on other objects. By exposing a connection point, a source allows sinks to establish connections to the source.

containment A composition technique for accessing one or more COM objects via a single interface. Containment allows one object to reuse some or all of the interface implementations of one or more other objects. The outer object manages requests to other objects, delegating implementation when it uses the services of one of the contained objects. See also aggregation.

control A discrete element of a user interface that allows a user to interact with application data.

critical section A segment of code that is not reentrant; that is, the code segment does not support concurrent access by multiple threads. Often, a critical section is used to protect shared resources.

D

data source name (DSN) The name of a data source that applications use to request a connection to the data source. For example, a data source name can be registered with ODBC through the ODBC Administrator program.

Database management system (DBMS) A layer of software between the physical database and the user. The DBMS manages all requests for database action (for example, queries or updates) from the user.

DBMS See Database management system.

DDV See Dialog data validation.

DDX See Dialog data exchange.

deadlock A state in which every process in a set of processes waits for an event or resource that only another process in the set can provide. For example, in data communications, a deadlock can occur when both the sending and receiving sockets are waiting on each other, or for a common resource.

debug version A version of a program built with symbolic debugging information.

debugger A program designed to help find errors in another program by allowing the programmer to step through the program, examine data, and check conditions.

default window procedure A system-defined function that defines certain fundamental behavior shared by all windows.

device context A data structure defining the graphic objects, their associated attributes, and the graphic modes affecting output on a device.

device driver A low-level software component that permits device-independent software applications to communicate with a device such as a mouse, keyboard, monitor, or printer.

dialog data exchange (DDX) In MFC, a method for transferring data between the controls of a dialog box and their associated variables. DDX is an easy way to initialize dialog box controls and gather user data input. See also DDV.

dialog data validation (DDV) In MFC, a method for checking data as it is transferred from the controls in a dialog box. DDV is an easy way to validate data entry in a dialog box. See also DDX.

dialog editor A resource editor that allows you to place and arrange controls in a dialog box template and to test the dialog box. The editor displays the dialog box exactly as the user will see it. While using the dialog editor, you can define message handlers and manage data gathering and validation with ClassWizard. See also dialog template.

dialog template A template used by Windows to create a dialog box window and display it. The template specifies the characteristics of the dialog box, including its overall size, initial location, style, and types and positions of its controls. A dialog template is usually stored as a resource, but templates can also be stored directly in memory. See also dialog editor.

dispatch identifier (dispatch ID )A 32-bit attribute value for identifying methods and properties in Automation. All accessor functions for a single property have the same dispatch ID.

dispatch interface In Automation, the external programming interface of a grouping of func-tionality exposed by the Automation server. For example, a dispatch interface might expose an application's mouse-clicking and text data entry functions. See also type library.

dispatch map In MFC, a set of macros that expands into the declarations and calls needed to expose methods and properties for Automation. The dispatch map designates internal and external names of object functions and properties, as well as data types of function arguments and properties.

document object An object that defines, stores, and manages an application's data. When the user opens an existing or new document, the application framework creates a document ob-ject to manage the data stored in the document.

document template In MFC, a template used for the creation of documents, views, and frame windows. A single application object manages one or more document templates, each of which is used to create and manage one or more documents (depending on whether the application is SDI or MDI). See also MDI, SDI.

document/view architecture A design methodology that focuses on what the user sees and needs, rather than on the application or what the application requires. This design is implemented by a set of classes that manage, store, and present application-specific data.

DSN See Data source name.

dual interface An interface that derives from IDispatch and supports both late-binding via IDispatch and early-binding (vtable bind-ing) via direct COM methods for each of its Automation methods.

dynaset A recordset (or set of records) with dynamic properties that is the result of a query on a database document. A dynaset can be used to add, change, and delete records from the underlying database table or tables. See also snapshot.

E

edit control Or edit box, text box. A rectangular control window that a user can use to type and edit text.

entry point A starting address for a function, executable file, or DLL.

environment variable A symbolic variable that represents an element of a user's operating system environment, such as a path, directory name, or configuration string. For example, the environment variable PATH represents the directories to search for executable files.

event 1. In ActiveX, a notification message sent from one object to another (for example, from a control to its container) in response to a state change or a user action. 2. More generally, any action or occurrence, often user-generated, to which a program can respond. Typical events include keystrokes, mouse movements, and button clicks.

event object A synchronization object that allows one thread to notify another that an event has occurred. Event objects are useful when a thread needs to know when to perform its task. For example, a thread that copies data to a data archive would need to be notified when new data is available. By using an event object to notify the copy thread when new data is available, the thread can perform its task as soon as possible.

external name In Automation, an identifier that a class exposes to other applications. Automation clients use the external name to request an object of this class from an Automation server.

F

file input/output (file I/O) The mechanism for making data persistent among program work sessions by creating files, reading from files, and writing to files.

File Transfer Protocol (FTP) A method of retrieving files to a home directory or directly to a computer using TCP/IP.

frame window In MFC, the window that coordinates application interactions with a document and its view. The frame window provides a visible frame around a view, with an optional status bar and standard window controls such as control menus, buttons to minimize and maximize the window, and controls for resizing the window.

free threading model A model in which an object can be used on any thread at any time. See also apartment-model threading, single threading model.

FTP See File Transfer Protocol.

G

GDI See Graphics Device Interface.

GIF See Graphics Interchange Format.

Graphics Device Interface (GDI) An executable program that processes graphical function calls from a Windows-based application, and passes those calls to the appropriate device driver, which performs the hardware-specific functions that generate output.

Graphics Interchange Format (GIF) A form of graphics compression.

H

Help context A string and a number (Help context ID) that an application passes during a call to Windows Help to locate and display a Help topic. See also Help project file.

Help project file A project file that controls how the Windows Help Compiler creates a Help (.hlp) file from topic files. The Microsoft Help Workshop is used to create a Help project file. The file name extension of a Help project file is .hpj.

Help topic The primary unit of information in a Help (.hlp) file. A topic is a self-contained body of text and graphics, similar to a page in a book. Unlike a page, however, a topic can hold as much information as required. If more information exists in a topic than the Help window can display, scroll bars appear to let the user scroll through the information.

HTML See Hypertext Markup Language.

HTTP See Hypertext Transfer Protocol.

hyperlink A link used to jump to another Web page. A hyperlink consists of both the display text and the URL of the reference.

Hypertext Markup Language (HTML) Derived from SGML, a markup language that is used to create a text document with formatting specifi-cations that inform a browser how to display the page or pages included in the document.

Hypertext Transfer Protocal (HTTP) The Internet protocol used by WWW browsers and servers to exchange information. The protocol makes it possible to use a client program to enter a URL (or click a hyperlink) and retrieve text, graphics, sound, and other digital information from a Web server. HTTP defines a set of commands and uses ASCII text strings for a command language. An HTTP transaction consists of a connection, request, response, and close.

I

IDL See Interface Definition Language.

IID See Interface Identifier.

in-process server A COM server implemented as a DLL that runs in the process space of an object's client. See also local server, remote server.

interface In COM, a set of related functions; a description of an abstract type.

Interface Definition Language (IDL) The OSF-DCE standard language for specifying the interface for remote procedure calls. See also MIDL.

Interface Identifier (IID) A globally unique identifier associated with an interface. Some functions take IIDs as parameters to allow the caller to specify which interface pointer should be returned. See also UUID.

Internet A global, distributed network of computers.

Internet Server Application Programming Interface (ISAPI) A set of functions for Internet servers, such as a Windows NT Server running Microsoft Internet Information Server (IIS).

intranet A network within an organization, usually connected to the Internet via a firewall, that uses protocols such as HTTP or FTP to enhance productivity and share information.

ISAPI See Internet Server Application Programming Interface.

ISAPI extension A DLL that can be loaded and called by some HTTP servers. Used to enhance the capabilities of applications that extend a Web server.

ISAPI filter An Internet server filter packaged as a DLL that runs on ISAPI-enabled servers.

L

licensing A COM feature that provides control over object creation. Licensed objects can be created only by clients that are authorized to use them. Licensing might afford different levels of functionality, depending on the type of license.

list-box control In Windows, a child window that contains a list of items that can be selected by the user. List boxes can permit the selection of one item or multiple items.

local server A COM server implemented as an executable file that runs on the same computer as the client application. Because the server application is an executable file, the local server runs in its own process. See also in-process server, remote server.

locking mode A strategy for locking records in a recordset during update. A record is locked when it is read-only to all users except the one currently entering data into it. See also optimistic locking, pessimistic locking.

M

marshaling In COM, the process of packaging and sending interface parameters across process boundaries.

MDI See Multiple document interface.

message A structure or set of parameters used for communicating information or a request. Messages can be passed between the operating system and an application, different applications, threads within an application, or windows within an application.

message box A window that displays information to the user. For example, a message box can inform the user of a problem that the application has encountered while carrying out a task.

MFC See Microsoft Foundation Classes.

Microsoft Foundation Classes (MFC) A set of C++ classes that encapsulate much of the functionality of applications written for Windows operating systems.

Microsoft Interface Definition Language (MIDL) Microsoft's implementation and extension of IDL. Processed by the MIDL compiler.

MIDL See Microsoft Interface Definition Language.

modal A restrictive or limiting interaction created by a given condition of operation. Modal often describes a secondary window that restricts a user's interaction with other windows. A secondary window can be modal with respect to its primary window or to the entire system. The user must close a modal dialog box before the application can continue operations. See also modeless.

modeless Not restrictive or limiting interaction. A modeless secondary window does not restrict a user's interaction with other windows. A modeless dialog box remains on a user's screen, available for use at any time, but also permits other user activities. See also modal.

Multiple document interface (MDI) The standard user interface architecture for Windows-based applications. An MDI application enables a user to work with more than one document at the same time. Each document is displayed within the client area of the application's main window. See also child window, client area, SDI.

mutex object In interprocess communication, a synchronization object in which state is signaled when it is not owned by a thread, and nonsignaled when it is owned. Only one thread at a time can own a mutex.

O

optimistic locking A recordset locking strategy in which records are left unlocked until explicitly updated. The page containing a record is locked only while the program updates the record, not while a user is editing the record. See also pessimistic locking.

P

persistent Lasting between program sessions, or renewed when a new program session is begun.

pessimistic locking A recordset locking strategy in which a page is locked once a user begins editing a record on that page. While the page is locked, no other user can change a record on that page. The page remains locked until records are updated or the editing is canceled. See also optimistic locking.

pixel The smallest addressable picture element (that is, a single dot) on a display screen or printed page.

platform The hardware and operating system that support an application. A platform sometimes is considered as the hardware alone, as in the Intel x86 platform.

primary key In a database program, a field or group of fields that uniquely identifies a record in a table. No two records in a table can have the same primary key value.

property The data associated with an object.

property page A grouping of properties presented as a tabbed page of a property sheet.

property sheet A type of dialog box that is generally used to modify the attributes of an external object, such as the current selection in a view. A property sheet has three main elements: the containing dialog box, one or more property pages shown one at a time, and a tab at the top of each page that the user clicks to select that page. An example of a property sheet is the Project Settings dialog box in Visual C++.

proxy An interface-specific object that packages parameters for methods in preparation for a remote method call. A proxy runs in the address space of the sender and communicates with a corresponding stub in the receiver's address space. See also stub, marshaling, unmarshaling.

Q

query A request for records from a data source. For example, a query can be written that requests "all invoices for Joe Smith," where all records in an invoice table with the customer name "Joe Smith" would be selected. See also recordset.

R

radio button In graphical user interfaces, a round button operated by the user to toggle an option or choose from a set of related but mutually exclusive options.

raw data Unprocessed, typically unformatted data. Raw data is a stream of bits that has not been filtered for commands or special characters. More generally, it is information that has been collected but not evaluated.

read-only Describes information stored in such a way that it can be played back (read) but cannot be changed (written).

record A collection of data about a single entity, such as an account or customer, stored in a table row. A record consists of a group of contiguous columns (sometimes called fields) that contain data of various types. See also recordset.

Record Field Exchange (RFX) The mechanism by which MFC ODBC classes transfer data between the field data members of a recordset object and the corresponding columns of an external data source. See also DDX.

record view In form-based data-access applications, a form view object in which controls are mapped directly to the field data members of a recordset object, and indirectly to the corresponding columns in a query result or table on the data source.

recordset A set of records selected from a data source. The records can be from a table, query, or stored procedure that accesses one or more tables. A recordset can join two or more tables from the same data source, but not from different data sources. See also record.

Red-green-blue (RGB) A mixing model, or method of describing colors, in light-based media such as color monitors. RGB mixes percentages of light-based colors (red, green, and blue) to create other colors. Windows defines these percentages as three 8-bit values called RGB values. Zero percentage of all three colors, or an RGB value of (0,0,0), produces black and 100 percent of all three colors, or an RGB value of (255,255,255), produces white.

reference count A count of the number of pointers that access, or make reference to, an object, allowing for multiple references to a single object. This number is decremented when a reference is removed; when the count reaches zero, the object's space in memory is freed.

referential integrity In database management, a set of rules that preserves the defined relationships between tables when records are entered or deleted. For example, enforcing referential integrity would prevent a record from being added to a related table when no associated record in the primary table exists.

registry In 32-bit Windows, the database in which configuration information is registered. This database takes the place of most configuration and initialization files for Windows and new Windows-based applications.

registry key A unique identifier assigned to each piece of information in the system registration database.

relational database A type of database or database management system that stores information in tables and conducts searches by using data in specified columns of one table to find additional data in another table.

remote server A COM server application, implemented as an executable file, that runs on a different computer from the client application using it. See also in-process server, local server.

RFX See Record Field Exchange.

RGB See Red-green-blue.

rich edit control In MFC, a window in which the user can enter and edit text. The text can be assigned character and paragraph formatting and can include embedded ActiveX objects.

root In a hierarchy of items, the single item from which all other items are descended. The root item has nothing dominating it in the hierarchy.

S

scrolling The process of moving a document in a window to permit viewing of any desired portion.

SEH See Structured Exception Handling.

semaphore A synchronization object that maintains a count between zero and a specified maximum value. A semaphore's state is signaled when its count is greater than zero and nonsignaled when its count is zero. The semaphore object is useful in controlling a shared resource that can support a limited number of users. This object acts like a gate that counts the threads as they enter and exit a controlled area, and that limits the number of threads sharing the resource to a specified maximum number.

serialization Also referred to as object persistence. In MFC, the process of writing or reading an object to or from a persistent storage medium, such as a disk file. The basic idea of serialization is that an object should be able to write its current state, usually indicated by the value of its member variables, to persistent storage. Later, the object can be recreated by reading, or deserializing, the object's state from storage.

server 1. In a network, a centrally administered computer that allows network access to all users. 2. An application or a process that responds to a client request.

server object An object that responds to a request for a service. A given object can be a client for some requests, and a server for other requests.

shell A piece of software, usually a separate program, that provides communication between the user and the operating system. For example, the Windows Program Manager is a shell program that interacts with MS-DOS.

Single document interface (SDI) A user interface architecture that allows a user to work with just one document at a time. Windows Notepad is an example of an SDI application. See also MDI.

single threading model A model in which all objects are executed on a single thread. Contrasts with multithreaded applications. See also apartment-model threading, free threading model.

smart pointer In C++, an object that implements the functionality of a pointer and additionally performs some action whenever an object is accessed through it. Smart pointers are implemented by overloading the pointer-dereference (-> ) operator.

snapshot In MFC, a recordset that reflects a static view of the data as it existed at the time the snapshot was created. See also dynaset, recordset.

SQL See Structured Query Language.

status bar A control bar at the bottom of a window, with a row of text output panes. The status bar is usually implemented as a message line (for example, the standard menu help message line) or as a status indicator (for example, the CAP, NUM, and SCRL indicators).

Structured Exception Handling (SEH) A mechanism for handling hardware- and software-generated exceptions that gives developers complete control over the handling of exceptions, provides support for debuggers, and is usable across all programming languages and computers.

Structured Query Language (SQL) A database sublanguage used to query, update, and manage relational databases.

stub 1. An interface-specific object that unpack-ages the parameters for that interface after they are marshaled across the process boundary, and makes the requested method call. The stub runs in the address space of the receiver, and communicates with a corresponding proxy in the sender's address space. 2. A function with an empty body; used as a placeholder.

synchronization object An object in which the handle can be specified in one of the wait functions to coordinate the execution of multiple threads. The state of a synchronization object is either signaled, which can allow the wait function to return, or nonsignaled, which can prevent the function from returning. More than one process can have a handle of the same synchronization object, making interprocess synchronization possible. See also mutex object, semaphore.

T

tab control A common control used to present multiple pages of information or controls to a user; only one page at a time can be displayed.

tab order The order in which the TAB key moves the input focus from one control to the next within a dialog box. Usually, the tab order proceeds from left to right in a dialog box, and from top to bottom in a radio group.

thread The basic entity to which the operating system allocates CPU time. A thread can execute any part of the application's code, including a part currently being executed by another thread. All threads of a process share the virtual address space, global variables, and operating system resources of the process.

toolbar A control bar based on a bitmap that contains a row of button images. These buttons can act like pushbuttons, check boxes, or radio buttons. See also status bar.

ToolTip A tiny pop-up window that presents a short description of a toolbar button's action. ToolTips are displayed when the user positions the mouse over a button for a period of time.

type library A file or component within another file that contains type information about exposed objects. Type libraries are created using either the MkTypLib utility or the MIDL compiler, and can be accessed through the ITypeLib interface.

U

UDA See Universal Data Access.

UNC See Universal naming convention.

Uniform Resource Locator (URL) The address of a resource on the Internet. URL syntax is in the form protocol://host/localinfo, where protocol specifies the means of fetching the object (such as HTTP or FTP), host specifies the remote location where the object resides, and localinfo is a string (often a file name) passed to the protocol handler at the remote location.

Universal Data Access (UDA) The Microsoft strategy for providing access to all types of information across the enterprise. UDA provides high-performance access to a variety of information sources.

Universal naming convention (UNC) The standard format for paths that include a local area network file server, as in \\server\share\path\filename.

Universally unique identifier (UUID) A GUID that identifies a COM interface. See also IID.

unmarshaling In COM, the process of unpacking parameters that have been sent across process boundaries.

URL See Uniform Resource Locater.

user-interface thread In Windows, a thread that handles user input and responds to user events independently of threads executing other portions of the application. User-interface threads have a message pump and process messages received from the system. See also worker thread.

UUID See Universally unique identifier.

V

variant In Automation, an instance of the VARIANT datatype, which can represent values of many different types, such as integers, floats, Booleans, strings, pointers, and so on.

view A window object through which a user interacts with a document.

vtable A table of function pointers, such as an implementation of a class in C++. The pointers in the vtable point to the members of the interfaces that an object supports. See also dual interface.

W

Win32 platform A platform that supports the Win32 API. These platforms include Intel Win32s, Windows NT, Windows 95, Windows 98, MIPS Windows NT, DEC Alpha Windows NT, and Power PC Windows NT.

window class A set of attributes that Windows uses as a template to create a window in an application. Windows requires that an application supply a class name, the window-procedure address, and an instance handle. Other elements can be used to define default attributes for windows of the class, such as the shape of the cursor and the content of the menu for the window.

window handle In the Win32 API, a 32-bit value (assigned by Windows) that uniquely identifies a window. An application uses this handle to direct the actions of functions to the window. A window handle has the HWND data type; an application must use this type when declaring a variable that holds a window handle.

window procedure A function, called by the operating system, that controls the appearance and behavior of its associated windows. The procedure receives and processes all messages to these windows.

wizard A special form of user assistance that guides a user through a difficult or complex task within an application. For example, a database program can use wizards to generate reports and forms. In Visual C++, the AppWizard generates a skeleton program for a new C++ application.

worker thread A thread that handles background tasks while a user continues to use an application. Tasks such as recalculation and background printing are examples of worker threads. See also user-interface thread.

World Wide Web (WWW) The portion of the global Internet that uses hypertext links to connect pages and resources in a way that lets a user reach any page from any other page.

WWW See World Wide Web.