Lesson 5: Managing VB Data

Welcome to Lesson 5 of our Visual Basic 6 Tutorial! In this lesson, you'll learn how to effectively manage data in VB6 applications. We'll cover data types, variables, constants, and scope with practical examples you can implement.

5.1 Understanding Visual Basic 6 Data Types

Data types in VB6 are essential for managing information effectively in applications. They are broadly categorized into numeric and non-numeric data types. This classification helps developers write efficient and accurate code.

5.1.1 Numeric Data Types in VB6

Numeric data types support mathematical operations. These include:

5.1.2 Non-Numeric Data Types in VB6

These types do not support mathematical operations. Common examples include:

5.1.3 Using Suffixes for Literals in VB6

Suffixes specify the data type of a literal value, allowing more accurate computations:

Also, enclose string literals in quotes and date literals within # symbols.

Private Sub Form_Load()
    Dim memberName As String
    Dim TelNumber As String
    Dim LastDay As Date
    Dim ExpTime As Date
    
    memberName = "Turban, John"
    TelNumber = "1800-900-888-777"
    LastDay = #12/31/2000#
    ExpTime = #12:00 AM#
End Sub

5.2 Working with Variables in VB6

Variables are placeholders for storing data in memory. You must name and declare them correctly for effective program design.

5.2.1 Naming Rules for Variables

Follow these rules when naming variables in VB6:

Examples:

5.2.2 Declaring Variables Explicitly

Use Dim for local variables, and combine multiple declarations using commas:

Private Sub Command1_Click()
    ' Declare multiple variables on one line
    Dim name As String, age As Integer, score As Double
    
    ' Fixed-length string declaration
    Dim yourName As String * 10
End Sub

5.2.3 Variable Scope in VB6

Variable scope determines where in your program a variable can be accessed:

5.3 Working with Constants

Constants hold values that do not change during program execution. Declared using the Const keyword.

' Declare a constant for Pi
Const Pi As Single = 3.142

' Declare a string constant
Const AppName As String = "VB6 Data Manager"

Practical Example: Calculate Area of a Circle

This program calculates the area of a circle using a constant and variables. The user can resize the circle shape and calculate its area.

' Declare variables and constant
Dim h, r, a, rad, area As Single
Const Pi As Single = 3.142

Private Sub CmdArea_Click()
    r = h / 2
    rad = r * 0.001763889  ' Convert to meters
    a = Pi * rad ^ 2       ' Area = πr²
    area = Round(a, 2)     ' Round to 2 decimal places
    
    ' Show result in a message box
    MsgBox ("The Area of the circle is " & area)
End Sub

Private Sub CmdResize_Click()
    ' Get height from user
    h = InputBox("Enter the value of height")
    
    ' Resize the circle shape
    MyShape.Height = h
End Sub

Next Lesson

Continue your VB6 journey with Lesson 6: Variables.

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