Here is a close-up look at creating user-defined functions in Visual Basic (VB).
Creating Your Own Functions
The general format of a function is as follows:
Public Function functionName (Arg As dataType,..........) As dataType
or
Private Function functionName (Arg As dataType,..........) As dataType
"Public" indicates that the function is applicable to the whole program, while "Private" indicates that the function is only applicable to a certain module or procedure.
Example of User-Defined Functions in Use
Here is an example of these functions in use. A user can calculate the future value of a certain amount of money he has today based on the interest rate and the number of years from now (supposing he will invest this amount of money somewhere). The calculation is based on the compound interest rate.
Public Function FV(PV As Variant, i As Variant, n As Variant) As Variant
'Formula to calculate Future Value(FV)
'PV denotes Present Value
FV = PV * (1 + i / 100) ^ n
End Function
Private Sub compute_Click()
'This procedure will calculate Future Value
Dim FutureVal As Variant
Dim PresentVal As Variant
Dim interest As Variant
Dim period As Variant
PresentVal = PV.Text
interest = rate.Text
period = years.Text
'This procedure will calculate Future Value
Dim FutureVal As Variant
Dim PresentVal As Variant
Dim interest As Variant
Dim period As Variant
PresentVal = PV.Text
interest = rate.Text
period = years.Text
FutureVal = FV(PresentVal, interest, period)
MsgBox ("The Future Value is " & FutureVal)
End Sub
MsgBox ("The Future Value is " & FutureVal)
End Sub
We try to implement a program which computes grades of a student based on the mark he scores.
Public Function grade(mark As Variant) As String
Select Case mark
Case Is >= 80
grade = "A"
Case Is >= 70
grade = "B"
Case Is >= 60
grade = "C"
Case Is >= 50
grade = "D"
Case Is >= 40
grade = "E"
Case Else
grade = "F"
End Select
End Function
Private Sub compute_Click()
grading.Caption = grade(mark)
End Sub
Private Sub End_Click()
End
End
End Sub
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