The Internet Encyclopedia (Volume 3)

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612 VISUALBASIC

Menu Bar

The Menu bar control is common to most Windows pro-

grams. A menu of related commands drops down when

an item on the Menu bar is clicked. These commands are

also invoked by clicking. Some menu items initiate an ac-

tion immediately, whereas others open additional menus

or dialog boxes.

Toolbar

The Toolbar control is also common in Windows pro-

grams. It provides icon-based access to the items in the

menus. In addition to the Standard Toolbar, Visual Basic

provides several specialized Tool bars for specific tasks

such as drawing. Click View on the Menu bar to see a

complete list of the available toolbars.

Project Explorer

The complete Visual Basic program is called a Project.

The Project Explorer window uses a hierarchical format

to list all forms, procedure modules, and objects in the

program. The Project Explorer allows the programmer to

instantly access any part of the project by clicking on an

item in the hierarchical list.

Properties Window

All objects have sets of properties that define how the

objects will appear and behave. Some properties can be

assigned values when a program is created, whereas oth-

ers are assigned values by the computer system while

the program executes. All properties that can be set by

the programmer are listed in the Properties window. Each

property is listed in the left column, with its current value

displayed in the column to its right. These values can be

changed by clicking the value in the right column and

entering a new value in its place. Property values can

also be changed during program execution by including

appropriate programming statements. See Creating a

Program in the Visual Basic Integrated Development En-

vironmentlater in this document for specific examples

of setting property values. Initially setting the Caption

property to nothing illustrates how to change a property

value in the Properties window. The Visual Basic state-

mentLabel1.Caption = “Hello!”is an example of changing

a property value with programming statements.

Form Layout Window

The Form Layout window shows the relative position of

the form on the screen during program execution.

Immediate Window

The Immediate window, sometimes called the Debug

window, is not present when Visual Basic is first started.

The Immediate window appears at the bottom of the

screen below the Code and the Form Layout windows.

When the program executes from within the develop-

ment environment the Immediate window displays expla-

nations of errors encountered. The information displayed

in the Immediate window, when used in conjunction with

the other debugging tools available in Visual Basic, re-

duces development time by speeding error identification

and correction.

Creating a Program in the Visual Basic

Integrated Development Environment

The following example will help illustrate the various

components of Visual Basic’s IDE. The task for this exam-

ple is to display a simple greeting when the user clicks a

button. Start Visual Basic and select Standard EXE from

the New Project dialog box. Begin creating the user in-

terface by placing a Command Button on the form. This

Command Button, when clicked, will cause the greeting

to appear on the screen. Click the Command Button icon

on the Toolbox, move to the lower center of the Form

Layout Window, and drag open a rectangular box. The

Command Button will appear when the mouse button is

released. With the Command Button still selected, click

Caption in the Properties Window. Change the value in

the right column to “Greet.” This will cause the text on

the button to be changed to “Greet.”

Next place a label on the form to display the greet-

ing. Select the Label icon on the Toolbox and drag open

a rectangular box in the upper center of the Form Layout

Window. The Label will appear when the mouse button is

released. Change the value in the Caption property of the

label to display nothing by erasing all characters in the

right column. The form should resemble Figure 2.

The interface is now complete. The controls, which are

objects, have inherited the operating characteristics and

appearance of similar Windows controls. Test the inter-

face by running the program. Click the Run symbol, the

right-pointing arrow in the Toolbar just below the Dia-

gram menu in the Menu Bar. The Visual Basic Develop-

ment Environment will run the program. Try clicking the

“Greet” button. It will act like a normal Windows but-

ton, but the greeting will not display when the button

is clicked. Clicking is an event that a user can perform

on the “Greet” command button. To display the greeting,

code must be entered into the event-handling procedure

to control what happens when the button is clicked.

Stop the program by clicking the Stop symbol in the

Tool Bar. It is the icon just below the Add-Ins menu in

the Menu Bar. Double click the “Greet” button on the

form. The view will shift from the Form Layout Window

to the Code Window. Visual Basic automatically enters the

header and footer needed to designate this as the proce-

dure that defines what happens when the “Greet” button is

clicked. Between the procedure header,Private Sub Com-

mand1Click(), and the procedure footer,End Sub, enter

the textLabel1.Caption=”Hello”.

Private Sub Command1_Click()

Label1.Caption="Hello!"

End Sub

This command will change the Caption property of the

Label control named Label1 to “Hello!” Run the program

again (click the Run symbol) and click the Greet Button.

The label will change from blank to “Hello!.” Stop the

program (click the Stop symbol). Save the program by

selecting the Save option from the File menu on the Menu

Bar. Following the instructions in the subsequent dialog

boxes to complete the save operation.