Upload
adolfo-damaceno
View
13
Download
0
Embed Size (px)
DESCRIPTION
Visual Basic Lesson 9_ Looping
Citation preview
9/22/12 Visual Basic lesson 9: Looping
1/3www.vbtutor.net/vb6/lesson9.html
Search
Lesson 9: Looping
Custom Search
Another procedure that involves decision makingis looping. Visual Basic allows a procedure to berepeated many times until a condition or a set ofconditions is fulfilled. This is generallycalled looping . Looping is a very useful feature of VisualBasic because it makes repetitive works easier. Thereare two kinds of loops in Visual Basic, the Do...Loop and the For.......Next loop
9.1 Do Loop The formats are
a) Do While condition
Block of one or more VB statements
Loop
b) Do Block of one or more VB statements Loop While condition
c) Do Until condition Block of one or more VB statements Loop
d) Do
Block of one or more VB statements
Loop Until condition
9.2 Exiting the Loop
Sometime we need exit to exit a loop prematurely
Example 9.1
Do while counter 1000.
The above example can be rewritten as
Do
num.Text=counter counter=counter+1
Loop until counter>1000
Example 9.2
Dim sum, n As Integer
Private Sub Form_Activate()
List1.AddItem "n" & vbTab & "sum"
Do
n = n + 1
Sum = Sum + n
List1.AddItem n & vbTab & Sum
If n = 100 Then
Exit Do
End If
Loop
End Sub
Explanation
In the above example, we compute thesummation of 1+2+3+4++100. In thedesign stage, you need to insert a ListBoxinto the form for displaying the output,named List1. The program uses theAddItem method to populate the ListBox.The statement List1.AddItem "n" & vbTab& "sum" will display the headings in theListBox, where it uses the vbTab functionto create a space between the headings nand sum.
Example 9.3 a
For counter=1 to 10
display.Text=counter
Example 9.3 b
For counter=1 to1000 step 10
Ads by Google Excel Tutorial Design Tutorial Visual Basic VB
BASIC ProgrammingLiberty BASIC gives you a power toolkit forWindows programming!www.libertybasic.com
VisualBasic 2008 TutorialLearn Visual Basic 2008 in your own. Free VisualBasic Tutorials.f1visualbasic.com
Top15 Accounting Software2012 Top 15 Accounting Software Rankings.Download Free Report.Business-Software.com/2012Report
PowerBasic vs VisualBasicFaster. No Run-Times. No Bloat! CGI, Macros, ASM,Reg Expressionswww.powerbasic.com
9/22/12 Visual Basic lesson 9: Looping
2/3www.vbtutor.net/vb6/lesson9.html
Sometime we need exit to exit a loop prematurelybecause of a certain condition is fulfilled. Thesyntax to use is known as Exit Do. You canexamine Example 9.2 for its usage.
9.3 For....Next Loop
The format is:
For counter=startNumber toendNumber (Step increment)
One or more VB statements
Next
Please refer to example 9.3a,9.3b and 9.3 c for itsusage.
Sometimes the user might want to get out fromthe loop before the whole repetitive process isexecuted, the command to use is Exit For. Toexit a For.Next Loop, you can place the Exit Forstatement within the loop; and it is normally usedtogether with the If..Then statement. Letsexamine example 9.3 d.
display.Text=counter
Next
1000 step 10
counter=counter+1
Next
Example 9.3 c
For counter=1000 to 5step -5
counter=counter-10
Next
*Notice that incrementcan be negative
Example 9.3 d
Private SubForm_Activate( )
For n=1to 10
If n>6then
Exit For
End If
Else
Print n
End If
End Sub
< Next Lesson>
Copyright 2008 Dr.Liew Voon Kiong . All rights reserved |Contact: [email protected]
[Privacy Policy]
Ads by Google Excel Tutorial Design Tutorial Visual Basic VB
9/22/12 Visual Basic lesson 9: Looping
3/3www.vbtutor.net/vb6/lesson9.html