visual basic v6 introduction

Introduction to Visual Basic Visual B eginners A ll-Purpose S ymbolic I nstruction C ode

Visual Basic is a tool that allows you to develop Windows (Graphic User Interface - GUI ) applications . is event-driven , meaning code remains idle until called upon to respond to some event.

Steps in Developing Application 1. Draw the user interface 2. Assign properties to controls 3. Attach code to controls

Draw the User Interface Visual Basic operates in three modes. Design mode - used to build application Run mode - used to run the application Break mode - application halted and debugger is available

7 Windows Main Window Form Window Toolbox Properties Window Form Layout Window Project Window Code Editor Window

Main Window consists of the title bar, menu bar, and toolbar.

Form Window is central to developing Visual Basic applications. It is where you draw your application.

Toolbox is the selection menu for controls used in your application.

Properties Window is used to establish initial property values for objects.

Form Layout Window shows where (upon program execution) your form will be displayed relative to your monitor’s screen.

Project Window displays a list of all forms and modules making up your application.

Code Editor Window Contains the actual Basic coding.

Assign Properties to Controls Naming Convention of Controls Object Prefix Example Form frm frmHello Command Button cmd, btn cmdExit, btnStart Label lbl lblStart, lblEnd TextBox txt txtTime, txtName Menu mnu mnuExit, mnuSave Check box chk chkChoice

Attach Code to Controls Code in a Visual Basic application is divided into smaller blocks called procedures. Event procedure syntax: object name_event () Ex. Command1_Click ()

Private Sub object name_event () End Sub _______________________________________ Private Sub Command1_Click () End Sub

Private Sub Command1_Click () object name.property = value End Sub _______________________________________ Private Sub Command1_Click () Text1.Text = "Hello, world!" End Sub

Variables Rules used in naming variables: No more than 40 characters. They may include letters, numbers, and underscore (_). The first character must be a letter. You cannot use a reserved word.

Variable Declaration 1. Default (variant) 2. Implicit Amount% = 300 3. Explicit four levels of scope Procedure level Procedure level, static Form and module level Global level

Procedure level Dim Variable name as Data type Ex. Dim Myint as integer Procedure level, static Static Variable name as Data type Ex. Dim Myint as integer

Form and module level Dim Variable name as Data type Ex. Dim Myint as integer Global level Global Variable name as Data type Ex. Dim Myint as integer

Procedure Routine1 has access to __, __, and __(…..) Procedure Routine2 has access to __, __, and __(…..) Procedure Routine3 has access to __, __, and __(…..)

Procedure Routine1 has access to X, Y, and A (loses value upon termination) Procedure Routine2 has access to X, Y, and B (retains value) Procedure Routine3 has access to X, Z, and C (loses value)

visual basic v6 introduction

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visual basic v6 introduction