programming-for-dummies

100
Fixing a Program with a Debugger
Step out
Suppose you start examining a subprogram line by line and suddenly want
to stop. As an alternative to stepping through the rest of the subprogram,
you can use the step out command, which tells the computer, “Stop stepping
through the subprogram line by line right now!”
Watching variables
When you step or trace through a program, line by line, you can see how the
program works. For more insight into your program’s behavior, you can
watch your variables.
You can read more about variables in Book II, Chapter 2. For now, just think
of a variable as a temporary place to store data, such as a number or a word.
Watching a variable lets you see what data your program is storing and using
at any given time. That way if your program is supposed to print a name but
actually prints that person’s phone number, you can step through your program
line by line, and watch to see which line stores the wrong data for the
program to print.
Not only can you “watch” how your program stores data, but a debugger
also lets you change data while your program is running. By changing data,
you can see how your program responds.
Figure 4-7:
The step
over
command
lets you skip
or “step
over” the
lines stored
in a
subprogram.
Private Sub cmdOK_Click
HandleReply()
txtQuestion.Focus()
End Sub
With the Step Over command, the debugger
treats the HandleReply() subprogram as a
single line of code.
Without the Step Over command, the debugger
runs every line of code in the HandleReply()
subprogram, forcing you to step through 23 lines
of code.
Public Sub HandleReply()
Dim I As Object
Dim NL As Object
Const LOWER As Short = 0
Const UPPER As Short = 9
Static TalkArray(UPPER) As String
Dim OldReply As String
Dim TempString As String
NL = Chr(10) & Chr(13)
OldReply = lblReply.Text
If lblConversation Text “” Then
For I = LOWER To UPPER - 2
TalkArray(I) = TalkArray(I+2)
Next I
End If
TalkArray(UPPER - 1)= “ELIZA:” &lblReplay.Text
TalkArray(UPPER) = txtQuestion.Text
TempString = “”
For I = LOWER to UPPER
TempString = TempString & TalkArray(I) & NL
Next I
lblConversation.Text = TempString
lblReply.Text = NewReply(OldReply, (txtQuestion.Text))
txtQuestion.Text = “”
End Sub