Creating Functions

A function is a reusable block of code that performs a task and returns a value. Unlike a sub procedure, which only executes actions, a function produces a result.

• Sub Procedure → performs task (no return value)
• Function → performs task + returns value

There are two types of functions:

• Built-in functions (e.g., Len, Format)
• User-defined functions (created by programmers)

Public Function functionName(arg As DataType) As DataType
    Statements
End Function

Key points:

• Public → accessible throughout project
• Private → limited to module/form
• Arguments pass values into function
• Function must return a value

BMI = weight / height²

Private Function BMI(height As Single, weight As Single) As Double
    BMI = weight / height ^ 2
End Function

LblBMI.Text = BMI(h, w)

This function calculates BMI and returns the value to be displayed.

Future Value Formula:

FV = PV * (1 + i / 100)^n

Private Function FV(pv As Single, i As Single, n As Integer) As Double
    FV = pv * (1 + i / 100) ^ n
End Function

This function calculates compound interest over time.

Arguments can be passed in two ways:

• ByVal → original value unchanged
• ByRef → original value modified

Private Function sqroot(ByRef x As Single) As Double
    x = x ^ 0.5
    Return x
End Function

Private Function sqroot1(ByVal y As Single) As Double
    y = y ^ 0.5
    Return y
End Function

Important:

• ByRef modifies original variable
• ByVal keeps original safe