Computer Programming Concepts and Visual Basic David I. Schneider

The second task performed by the addition program also can be handled by a Sub procedure.
The values of the two numbers, however, must be transmitted to the Sub procedure.
This transmission is called passing.
EXAMPLE 2
The following revision of the program in Example 1 uses a Sub procedure to accomplish the second task.
The statement Call Add(2, 3) causes execution to jump to the Private Sub Add(num1 As Single, num2 As
Single) statement, which assigns the number 2 to num1 and the number 3 to num2.
Call Add(2, 3)
Private Sub Add(num1 As Single, num2 As Single)
After the lines between Private Sub Add (num1 As Single, num2 As Single) and End Sub are executed,
execution continues with the line following Call Add(2, 3), namely, the End Sub statement in the event
procedure. Note 1: When you create the Sub procedure Add, you must type in “(num1 As Single, num2
As Single)” after leaving the Add Procedure dialog box.
Private Sub cmdAdd_Click()
‘Display the sum of two numbers
picResult.Cls
Call ExplainPurpose
picResult.Print
Call Add(2, 3)
End Sub
Private Sub Add(num1 As Single, num2 As Single)
‘Display numbers and their sum
picResult.Print “The sum of”; num1; “and”; num2; “is”; num1 + num2
End Sub
Private Sub ExplainPurpose()
‘Explain the task performed by the program
picResult.Print “This program displays a sentence”
picResult.Print “identifying two numbers and their sum.”
End Sub
Sub procedures make a program easy to read, modify, and debug. The event procedure
gives a description of what the program does and the Sub procedures fill in the details.
Another benefit of Sub procedures is that they can be called several times during the execution
of the program. This feature is especially useful when there are many statements in the
Sub procedure.
EXAMPLE 3
The following extension of the program in Example 2 displays several sums.
Private Sub cmdAdd_Click()
‘Display the sums of several pairs of numbers
picResult.Cls
Call ExplainPurpose
picResult.Print
Call Add(2, 3)
Call Add(4, 6)
Call Add(7, 8)
End Sub
Sub Procedures, Part I 75