Visual Basic (2008 Express)
Standard Functions

VB has many of these. A simple example is Len - the function that calculates the number of characters in a string.

The code here assigns the number of characters in a string called Surname to an integer variable called Count.

 

Dim Surname As String
Dim Count As Integer

Surname = "Johnson"

Count = Len(Surname)

 

 This code would assign the value 7 to the variable Count.
 
Sub-routines

To define a subroutine in VB, a programmer needs to give it a name. 

Here is an example of a subroutine named InitialiseTextBox that initialises some of the properties of a TextBox...

 
Private Sub InitialiseTextBox(ByVal MyTextBox As TextBox)

MyTextBox.Width = 50
MyTextBox.BackColor = Color.Beige
MyTextBox.ForeColor = Color.Chocolate
MyTextBox.Font = New Font("Verdana", 18)

End Sub

 

 If you want to use this subroutine on other forms, replace the word Private by the word Public.
The programme would need to tell the subroutine which TextBox is to be initialised. This is done through the parameter MyTextBox (you can name it whatever you like!).

The next code uses this subroutine to initialise a TextBox called txtCount and outputs the number of letters in the string Surname.
Dim Surname As String
Dim Count As Integer

Surname = "Johnson"

Count = Len(Surname)

InitialiseTextBox(txtCount)

txtCount.Text = Count

 

The output is displayed in the TextBox.
 
Functions

A Function returns an answer - the type of the answer has to be declared in the function heading...

Here is an example of a function called Lettern that calculates how many times the letter n occurs in a string.

 
Private Function Lettern(ByVal MySurname As String) As Integer

Dim Count As Integer
Dim i As Integer

'Initialise count to zero
Count = 0

For i = 1 To Len(MySurname)
    If Mid$(MySurname, i, 1) = "n" Then
        Count = Count + 1
    End If
Next

'Assign value to the function
Lettern = Count

End Function

 

 Note that the value of the function must always be assigned to it.

A parameter called MySurname is used to pass the identifier of the string to the function.
To use this function to output the answer into our Textbox...

 
Dim Surname As String
Dim Count As Integer

Surname = "Johnson"

Count = Len(Surname)

InitialiseTextBox(txtCount)

'This next instruction calls the function
txtCount.Text = Lettern(Surname)

 
 
Modules
Useful subroutines and functions should be placed in a Module. This module can then be used in other programs.

Subroutines and functions placed in the Module and declared Public, can be used on any form in the current project.

To create a Module in VB, right-click on the name of the Project and Add...Module

 

The module will appear in the Solution Explorer.

This module is saved as a separate file and can be imported into other programming projects.

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