Computer Programming Concepts and Visual Basic David I. Schneider

464 Computer Programming Concepts and Visual Basic
6. Click on the End icon to end the program.
7. If desired, step through the program again, entering a different age and predicting
which Case clause will be acted upon. (Some possible ages to try are 12, 14,
18, 33, and 67.)
STEPPING THROUGH A PROGRAM CONTAINING A DO LOOP: SECTION 5
Do Loops
The following walkthrough demonstrates use of the Immediate window to monitor the value
of a condition in a Do loop that searches for a name.
1. Access Windows’ Notepad, enter the following line of data, and save the file on
the A drive with the name DATA.TXT
Bert, Ernie, Grover, Oscar
2. Return to Visual Basic. Create a form with a command button (cmdButton) and
a picture box (picBox). Set the AutoRedraw property of the picture box to True.
Then double-click on the command button and enter the following procedure:
Private Sub cmdButton_Click()
‘Look for a specific name
Dim searchName As String, nom As String
picBox.Cls
searchName = InputBox(“Name:”) ‘Name to search for in list
Open “A:DATA.TXT”For Input As #1
nom = “”
Do While (nom [%6][lt>]20searchName) And Not EOF(1)
Input #1, nom
Loop
Close #1
If nom = searchName Then
picBox.Print nom
Else
picBox.Print “Name not found”
End If
End Sub
3. Press F8 and click on the command button. The heading of the event procedure
is highlighted in yellow.
4. Double-click on the variable searchName, click the right mouse button, click on
“Add Watch,” and click on OK. The variable searchName has been added to the
Watch window.
5. Repeat Step 4 for the variable nom.
6. Drag the mouse across the words
(nom searchName) And Not EOF(1)
to highlight them. Then click the right mouse button, click on “Add Watch,” and
click on OK. Widen the Watch window as much as possible in order to see the
entire expression.
7. Press F8 three more times to execute the picBox.Cls statement and the statement
containing InputBox. Enter the name “Ernie” at the prompt.
8. Press F8 repeatedly until the entire event procedure has been executed. Pause
after each keypress and notice how the values of the expressions in the Watch
window change.
9. Click on the End icon to end the program.