Computer Programming Concepts and Visual Basic David I. Schneider

74 Computer Programming Concepts and Visual Basic
Consider the following program that calculates the sum of two numbers. This program
will be revised to incorporate Sub procedures.
Object Property Setting
frmArithmetic Caption Arithmetic
cmdAdd Caption Add Numbers
picResult
Private Sub cmdAdd_Click()
Dim num1 As Single, num2 As Single
‘Display the sum of two numbers
picResult.Cls
picResult.Print “This program displays a sentence “
picResult.Print “identifying two numbers and their sum.”
picResult.Print num1 = 2 num2 = 3
picResult.Print “The sum of”; num1; “and”; num2; “is”; num1 + num2
End Sub
[Run, and then click the command button. The following is displayed in the picture box.]
This program displays a sentence
identifying two numbers and their sum.
The sum of 2 and 3 is 5
The tasks performed by this program can be summarized as follows:
Explain purpose of program.
Display numbers and their sum.
Sub procedures allow us to write and read the program in such a way that we first focus on
the tasks and later on how to accomplish each task.
EXAMPLE 1
The following program uses a Sub procedure to accomplish the first task of the preceding program. When
the statement Call ExplainPurpose is reached, execution jumps to the Sub ExplainPurpose statement. The
lines between Sub ExplainPurpose and End Sub are executed, and then execution continues with the line
following the Call statement.
Private Sub cmdAdd_Click()
Dim num1 As Single, num2 As Single
‘Display the sum of two numbers
picResult.Cls
Call ExplainPurpose
picResult.Print
num1 = 2
num2 = 3
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