Kamus Istilah Visual Basic

Active Server Page (ASP) A Web-based application containing a combination of HTML, ActiveX components, and VBScript code. Active Server Pages can be used to dynamically provide different content for different users when viewed through each user's Web browser.

ActiveX A set of technologies based on Microsoft's Component Object Model (COM) for creating reusable binary objects.

ActiveX component (Formerly OLE automation server) A physical file that contains classes from which objects can be defined. ActiveX components generally have file extensions .exe, .dll, or .ocx.

ActiveX control An object that can be placed on a form so that users can interact with applications. ActiveX controls have events, properties, and methods and can be incorporated into other controls. ActiveX controls have an .ocx file extension.

ActiveX Data Objects (ADO) An object model--including data connection, data manipulation, and recordset objects--used for data access. ADO is an OLE DB consumer.

ActiveX DLL An ActiveX in-process component, an object that requires another application's process space. See also ActiveX EXE.

ActiveX document A Visual Basic application that can be viewed within a container application such as Microsoft Internet Explorer (version 3.0 or later) or Microsoft Office Binder. ActiveX documents don't require HTML code in order to be viewed or manipulated.

ActiveX EXE An ActiveX out-of-process component, an object that runs in its own address space. See also ActiveX DLL.

add-in A software component that extends Visual Basic's capability. Some add-ins, such as the Visual Basic Class Builder Utility add-in, are included with Visual Basic; many more are available from third-party sources. Within the IDE, you use the Add-In Manager to install and remove add-ins.

ambient property A property that a child object can assume during runtime. Ambient properties are controlled by a container object and are used so that objects within the container can take characteristics of the container.

ANSI The acronym for American National Standards Institute. ANSI provides a unique integer code for a character set that includes 256 characters. ANSI includes the 128-character ASCII character set and contains international letters, symbols, and fractions.

API The acronym for Application Programming Interface. An API is a set of functions that are exposed by a software module and provide access to the services the module provides. In Windows, the API is a set of core functions that allow direct access to many operating system-provided services, such as window management and printer services. The Windows API consists of three main files: user32.dll, gdi32.dll, and kernel32.dll.

application One or more software components that do some action or provide some service, a compiled Visual Basic project. Other examples of applications include Microsoft Visual Basic and Microsoft Word. Also known as a program.

argument Data sent to a procedure. An argument can be a constant, a variable, or some other expression.

array An indexed group of related data. Elements within an array must be of the same data type (such as all integers or all strings), and each element has a unique, sequential index number.

ASCII The acronym for American Standard Code of Information Interchange. ASCII provides a unique integer code for a character set that includes 128 numbers, letters, and symbols found on a standard U.S. keyboard. A subset of the ANSI character set. In Visual Basic, the ASC function returns the ASCII value of a character.

authentication The process by which the identity of an ActiveX control is proven to a Web browser. During authentication, the Web browser determines that the control meets a predetermined set of criteria, in essence, verifying that the control hasn't been tampered with and that it will behave in the way the control's developer originally intended.

automation server See ActiveX component.

bind To connect an object to a data source. See bound control.

bit The smallest amount of data storage available on a computer. A bit is either 0 or 1.

bookmark A marker for a specific location. A bookmark can be a specific record in a database, a line of code within a project, or a specific Web page.

Boolean A binary data type. Boolean values are 16-bit (2-byte) values that can hold the True or False constants or their equivalents (-1 and 0). The Boolean data type uses the prefix bln but doesn't have a type-declaration character.

bound control A data-aware control attached to a database through a Data control. At runtime, when users manipulate the Data control by changing from one row of the database to the next, the bound control changes to display the data found in the columns of the new row. If users change the data stored in a row, the new data is saved to the database when the users switch to a new row.

breakpoint A specific line within a block of code where program execution automatically stops (during runtime). Breakpoints are user selectable. You can toggled them on and off during design time by pressing F9.

browser An application used to browse content on the Web. Browsers, such as Microsoft Internet Explorer, can show HTML pages, Active Server Pages, and various other types of content.

buffer string A temporary holding location in memory for data that will be parsed or otherwise modified. For example, if an application were to take two string values from a user and then extract a specific section from their sum, each value would be placed in a buffer string. Then these would be concatenated (and placed into another buffer string) before the desired value is parsed from the input data.

Byte An 8-bit data type that can hold numbers in the range of 0-255. The Byte data type uses the prefix byt but doesn't have a type-declaration character. Bytes are the basis for all Visual Basic data types; for example, the Single data type is a 4-byte (32-bit) number.

CAB file Short for cabinet file. A group of files compressed into one larger file to conserve disk space. CAB files are often used to distribute applications. During installation, the Setup program extracts files from the CAB file and copies them to the appropriate location on the hard disk.

call To transfer control of an application to a different procedure. Procedures are sometimes called with the Call keyword.

child object An object contained within another object (its parent). See object.

class A template used to create user-defined objects. A class defines an object's properties and methods. All instances created from the class use the properties and methods defined by the class.

class module A module that defines a class. See module.

code block A selection of code. A code block usually consists of all lines necessary to complete a specific task within the application.

COM The acronym for Component Object Model. A standard by which applications can expose objects to the system for use by other applications and, conversely, by which applications can use objects that have been exposed by other applications.

compile To prepare code for execution. In Visual Basic, code can be compiled into either P-code (which results in faster compilation) or native code (which results in faster execution). The type of compilation can be selected from the Compile page of the Project Properties dialog box.

component object An object that supports automation through exposed properties and methods. Examples of component objects include ActiveX controls, ActiveX documents, and ActiveX code components.

compressed file A file that has been modified to take up less space when stored on the hard drive. Generally, compressed files can't be opened or manipulated until they're decompressed.

concatenate To join two or more strings in an expression.

conditional statement A logical statement involving a comparison, which yields a Boolean (True or False) value.

constant A variable or object whose value doesn't change.

constituent control A control that's encapsulated inside another ActiveX control to provide some of the constituent control's functionality when using the ActiveX control.

context-sensitive help Information about a specific concept or object within in an application that users can easily find. To access context-sensitive help, press Shift+F1 or click the What's This? help (question mark) button; then select the confusing item.

control An object that can be manipulated at design time or runtime to present or change data. Controls are manipulated by changing properties during design time and by calling methods or responding to events during runtime.

control array An indexed group of similar controls that are of the same type and have the same name. Individual elements within the control array are identified by a unique index number.

coolbar A type of toolbar characterized by flat buttons that raise when the mouse pointer moves over them and, when clicked, they depress. This is the type of toolbar found in the Visual Basic IDE. The Coolbar object is used to create user-modifiable coolbars.

Currency A numeric data type particularly suited to store money data. Currency values are 64-bit (8-byte) integers, scaled by 10,000 to provide four digits to the right of the decimal point. Currency values use the prefix cur and the type-declaration character @ (the at sign).

data consumer An object that's bound to a data provider. A data consumer lets programmers connect to a data source and manipulate information within it.

data member Private variable of a class. Data members are seen only by the class that defines them.

data provider A data source that exposes information for data access, such as Microsoft Jet, Microsoft SQL, or Oracle.

data type A set of rules describing a specific set of information, including the allowed range and operations and how information is stored. Data types in Visual Basic include Integer, String, Boolean, and Variant.

Date A numeric data type used to represent dates. Date values are 64-bit (8-byte) floating-point numbers that represent dates from January 1, 100, to December 31, 9999, and times from 0:00:00 to 23:59:59. The Date data type uses the prefix dat but doesn't have a type- declaration character.

DCOM The acronym for Distributed Component Object Model. An extension of COM by which applications can expose objects to computers across a network, and, conversely, by which computers can use objects that have been exposed from across a network.

Decimal A numeric data type, ranging from 0 to 28, used to specify the number of digits to the right of the decimal point. Decimal values are 96-bit (12-byte) unsigned integers, so with a scale of 28, the largest possible Decimal value is +/-7.9228162514264337593543950335; with a scale of 0, +/-79,228,162,514,264, 337,593,543,950,335. The Decimal data type must be used with a Variant, uses the prefix dec, and doesn't have a type-declaration character.

deployment The period during which an application is distributed for use by customers or by other applications.

design time The time spent creating forms and writing functions during the creation of an application. Forms and functions can be altered only during design time. See runtime.

designer An object or application that's used as a basis for creating more advanced objects or applications.

destination system The system on which an application will be installed and used.

device independence The concept that software components don't directly control hardware devices. Device- independent software controls hardware by manipulating objects that abstract and expose the functionality of a class of hardware devices.

DLL The acronym for dynamic link library. An executable file containing a set of functions that other applications can call during runtime. DLLs generally don't have a graphical user interface; instead, they're usually accessed by applications without user intervention.

Document Object Model (DOM) A method for storing information so that a document can display its content in a variety of in-place views.

domain name A unique name that identifies an Internet or network server, such as www.mcp.com or www.microsoft.com. Domain names are actually text representations of numeric IP addresses and must be registered with international authorities such as InterNIC.

Double A numerical data type. Double values are 64-bit (8-byte) floating-point number. Double values use the prefix dbl and the type-declaration character # (the pound sign).

dynamic A changing object or expression.

Dynamic HTML (DHTML) A series of extensions to the HTML language that enable an HTML page to be dynamically modified. A group of HTML pages that work together can be used to create a Web-based application. DHTML applications contain objects and events and are processed on the client within the Web browser.

dynaset A recordset that can include data from one or more tables from a database. A dynaset can be used to view or modify data contained in the underlying database.

early binding A technique that an application uses to access an object. In early binding, objects are defined from a specific class. Early binding is often faster than late binding because the application doesn't have to interrogate the object at runtime to determine the object's properties and methods. In Visual Basic, early binding enables the AutoComplete features to work correctly.

Easter egg A hidden signature within an application, included by programmers to demonstrate that they wrote it. Activating Easter eggs often requires a complex set of user actions.

element A single member of an array. Each element of an array is assigned a unique index value, which is used to locate and manipulate specific elements in an array.

encapsulation The act of placing code or data in a location, such as a module or control, that's isolated from the rest of an application. Encapsulation hides both the implementation details and the internal complexity of an object but still enables the application to use functions contained within it.

enterprise computing A computing model in which multiple users access applications and data stored on a server. In an enterprise computing environment, multiple servers and multiple networks can be linked together. This is an advanced form of general networking in which users can share information directly, without the use of a dedicated server.

entry point The starting point in the code of an application. In Visual Basic 6, entry points include a Sub Main procedure or a Form_Load event.

event A signal fired by the operating system in response to a user action. For example, when a user clicks (and holds down) a mouse button, a MouseDown event is sent by the operating system. The active application intercepts this signal and executes the code attached to the MouseDown event.

event-driven programming A method of programming in which blocks of code are run as users do things or as events occur while a program is running. This varies from procedural programming, in which code blocks are contained within a module and called from other procedures.

event procedure The place in a project where code is written to respond to an event. Event procedures are named by joining the object name with the event name, such as cmdButton_Click().

extensibility The capability to extend an object's or application's functionality through the use of a programming language or an add-in.

field A discrete element of a record in a database, a column in a database--for example, a database of music CDs might have many fields, including the CD title, artist name, and CD label.

file A unit of storage on an external storage device such as a hard disk retrievable block of data. Usually stored on a hard drive, files can contain executable programs, word processor documents, or bitmap picture files. In Visual Basic, each form, module, and project are saved as a file.

file handle A structure that identifies and provides access to a file on disk.

File Transfer Protocol (FTP) A method used to transfer files between computers, across a network, or over the Internet by using the TCP/IP network protocol.

flag A Boolean (True or False) variable used to determine whether a condition has been met or an event has occurred. For example, the flag blnPasswordSet would be set to True when a password is set and to False when the password is cleared.

flat-file database A database file in which every record contains all the information required to describe it. Flat-file databases often contain redundant information. For example, every record in a flat-file database of music CDs would require multiple fields to describe the contact information for the artist's fan club. See also relational database.

focus The state in which an object can receive input from the mouse or keyboard. At any given time, only one object can have focus; this object is usually highlighted with a different color and contains the text cursor, where appropriate.

form The basis of an application's graphical user interface. Forms contain objects with which users manipulate data and otherwise control an application.

Form Designer A part of the Visual Basic 6 Integrated Development Environment. You use the Form Designer to create an application's graphical user interface by placing objects on forms during design time. At runtime, objects appear where they have been placed on the forms.

Form Layout window A part of the Visual Basic 6 Integrated Development Environment (MDI version only). The Form Layout window is used to position an application's forms during design time, visually rather than through code. At runtime, forms appear where they have been placed in the Form Layout window.

function A procedure, beginning with Function functionname() and ending with End Function, that returns a value to the calling procedure when it's complete.

Get A Visual Basic keyword, the part of a Property procedure that gets the value of a property.

global variable A variable that can be accessed from anywhere within a program and maintains its value while the program is being run. Global variables are defined within code modules with the Public keyword.

gotcha A detail that can cause problems when overlooked.

graphical user interface (GUI) A set of forms and objects that enable users to view and manipulate data and otherwise control an application. A graphical user interface is the part of the application that sits between users and an application's underlying procedures.

hard-coding The act of setting a value by directly coding it into the application without allowing for a way to easily change it. For example, the hard-coded statement Set picPictureBox.Picture= LoadPicture("C:\windows\bubbles.bmp") won't work if the file bubbles.bmp is moved from the Windows folder, and it doesn't allow users to change the image loaded into the PictureBox. To avoid this situation, it would be better to define a string variable that contains the image's path and filename and then provide tools (such as an Open common dialog box) to help users search for it.

header A commented section of code at the beginning of a procedure, usually placed before the Sub or Function statement. The header describes the purpose of the procedure, specifies all variables declared within it, and can contain information identifying the developer(s) who wrote it.

help compiler An application used to combine information into a help file.

help context ID A number that defines a position within a help file. The Windows help system uses context IDs to move to new locations within help files as users navigate through the help system.

high-level language A computer language, such as Visual Basic, that can simplify coding by enabling programmers to write code with highly developed functions and keywords. See also low-level language.

hovering The act of holding the mouse pointer over an object. For example, a ToolTip can appear when the pointer hovers over a command button.