Chapter 7
Part A

Procedures

A block of code with a specific task

Sub <Procedure Name>( )
   Command
   Command
   Command
   etc.
End Sub

Using Procedures

• Defined in text editor (outside of existing procedures)
• Called by name
• Execute when they are called
• Return to where they were called from
  

Let's define the following:
    subroutine in Form_Load

Private Sub Form_Load()
    SubRoutine1
    SubRoutine2
     SubRoutine3
End Sub

Adding Procedures

Type the word Sub plus procedure name

Sub Subroutine1

When you hit Enter, VB adds the parentheses and the End Sub

Sub Subroutine1( )
|
End Sub

Calling Procedures

Define the following subroutine in Form_Load

Defining Procedures

Returns error message

• Subroutines need to be defined

  Sub Subroutine1( )
         MsgBox "This is subroutine 1"
  End Sub

• Repeat for Subroutine2 and Subroutine3
• Run program

Value Parameters

• Values subroutines need to do their task
• Value Parameters

  Example:

Private Sub Form_Load()
Dim intNum As Integer
    intNum = 1
    MsgBox "The value before call” & intNum
    AddOne intNum ‘this is the “call”
    MsgBox "The value after call " & intNum
End Sub


Now lets write the subroutine:

Sub AddOne(ByVal intN As Integer)
    intN = intN + 1
End Sub

Results:

 

The procedure leaves intNum unaffected

• Reference Parameters

  Example:

  Now a simple change

  Sub AddOne(ByRef intN As Integer)
       intN = intN + 1
  End Sub

Results:

 

Note the different results!

Scope of Variables

Global

• Defined in General Declarations
• Known throughout form
  

Local

• Defined in subroutine
• Only known in that subroutine
  

“Lifespan” of variables

Global

• Born when program compiled
• Die when program ends
  

Local

• Born when subroutine called
• Die when subroutine concludes
  

Static Variable

• Only known locally like local value
• “Lifespan” like global
• Declared in subroutine with Static rather then Dim