Control structures - 1.Branching - 1. IF Statement ;- Example

Savings Account - 

1.   Note the acceptable ASCII codes are 48 through 57 (numbers), 46 (the decimal point), and 8 (the backspace key).  In the code, we use symbolic constants for the numbers and backspace key.  Such a constant does not exist for the decimal point, so we will define one with the following line in the general declarations area:

      Const vbKeyDecPt = 46

     

2.      Add the following code to the three procedures:  txtDeposit_KeyPress, txtInterest_KeyPress, and txtMonths_KeyPress.

      Private Sub txtDeposit_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

       Beep

      End If

      End Sub

     

      Private Sub txtInterest_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

       Beep

      End If

      End Sub

     

      Private Sub txtMonths_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

 Beep

      End If

      End Sub

     

(In the If statements above, note the word processor causes a line break where there really shouldn’t be one.  That is, there is no line break between the words Or KeyAscii and = vbKeyDecPt.  One appears due to page margins.  In all code in these notes, always look for such things.)

3.      Rerun the application and test the key trapping performance.

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Control structures - 1.Branching - 3. GoTo Statement

     

     Another branching statement, and perhaps the most hated statement in programming, is the GoTo statement.  However, we will need this to do Run-Time error trapping.  The format is GoTo Label, where Label is a labeled line.  Labeled lines are formed by typing the Label followed by a colon. 

     

·         GoTo Example:

     

When the code reaches the GoTo statement, program control transfers to the line labeled Line10.

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Control structures - 1.Branching - 1. IF Statement ;- Example

Savings Account - 

1.   Note the acceptable ASCII codes are 48 through 57 (numbers), 46 (the decimal point), and 8 (the backspace key).  In the code, we use symbolic constants for the numbers and backspace key.  Such a constant does not exist for the decimal point, so we will define one with the following line in the general declarations area:

      Const vbKeyDecPt = 46

     

2.      Add the following code to the three procedures:  txtDeposit_KeyPress, txtInterest_KeyPress, and txtMonths_KeyPress.

      Private Sub txtDeposit_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

       Beep

      End If

      End Sub

     

      Private Sub txtInterest_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

       Beep

      End If

      End Sub

     

      Private Sub txtMonths_KeyPress (KeyAscii As Integer)

      ‘Only allow number keys, decimal point, or backspace

      If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyDecPt Or KeyAscii = vbKeyBack Then

        Exit Sub

      Else

       KeyAscii = 0

 Beep

      End If

      End Sub

     

(In the If statements above, note the word processor causes a line break where there really shouldn’t be one.  That is, there is no line break between the words Or KeyAscii and = vbKeyDecPt.  One appears due to page margins.  In all code in these notes, always look for such things.)

3.      Rerun the application and test the key trapping performance.

.