1. Case & Repetitive Statements
Skill Area 306.2
Materials Prepared by Dhimas Ruswanto, BMm

2. Lecture Overview Case Statement Do While…Loop Do…Loop While
Do Until…Loop
Do…Loop Until
For…Next

3. Case Statement

4. Case Statement
Its objective is to check several possible constant values for an expression.
Something similar to what we did at the beginning of this section with the concatenation of several if and else if instructions.

5. Case Statement Select Case (expression) Case constant1
The syntax for the case statement is as follows:
Select Case (expression)
Case constant1
group of statements 1
Case constant2
group of statements 2
. . .
Case Else
group of statements
End Select

6. Case Statement (Example)
Dim num As Integer Dim msg As String num = Val(txtDisplay.Text) Select Case num Case 1 To 50 msg = "Pass“ Case 71, 76, 79 To 100 msg = "High" Case Is > 101 msg = "Higher“ Case Else msg = "Invalid“ End Select MsgBox(msg)

7. Case Statement (Example)
Both of the following code fragments have the same behavior:
Case example
if-else equivalent
Select Case name
Case "Adam"
MsgBox(“Position is MANAGER")
Case "Bob”
MsgBox(“Position is SUPERVISOR")
Case "Charlie”
MsgBox(“Position is ACCOUNTANT")
Case "Eve"
MsgBox(“Position is SECRETARY")
Case Else
MsgBox("No data found")
End Select
If name = "Adam" Then
ElseIf name = "Bob" Then
ElseIf name = "Charlie" Then
ElseIf name = "Eve" Then
Else
End If

8. Types of repetition statements:
A repetition statement can repeat actions, depending on the value of a condition (which can be either truer or false)
Types of repetition statements:
Do While…Loop
Do…Loop While
Do Until…Loop
Do…Loop Until

9. Do While…loop & do Loop…while

10. Do While..Loop & Do..Loop While
Do While..Loop & Do..Loop While – a control statement that executes a set of body statements while its loop-continuation condition is True
Loop-continuation condition – the condition used in a repetition statement that enables repetition to continue while the condition is True and that causes repetition to terminate when the condition becomes False
Syntax:
Do While loop-continuation condition
block of statements
Loop Do
block of statements
Loop While loop-continuation condition

11. Do While..Loop & Do..Loop While
Example:
Do While product <= 50
product += 3
Loop Do
product +=3
Loop While product <= 50
In the Do While..Loop statement, the loop-continuation condition is tested at the beginning of the loop, before the body of the loop is performed.
In Do..Loop While statement performs the loop-continuation condition after the loop body if performed.
Therefore, in a Do..Loop While statement, the loop body always executes at least once. A Do While..Loop executes only if its loop-continuation condition evaluates to true.

12. Do While..Loop & Do..Loop While
Example:
Dim number As Integer
Do While number < 4 
MsgBox("The number is " & number) 
number = number + 1
Loop
Dim number As Integer
Do  
MsgBox("The number is " & number) 
number = number + 1
Loop While number < 4

13. Do While..Loop & Do..Loop While
Example:
Dim number As Integer
Do While number < 4 
MsgBox("The number is " & number) 
number = number + 1
Loop
The output of the code above will be different with the code below
Dim number As Integer
Do While number < 4  
number = number + 1
Loop
MsgBox("The number is " & number) 

14. Do until…loop & do Loop…until

15. Do Until..Loop & Do..Loop Until
Do Until..Loop & Do..Loop Until– a control statement that executes a set of body statements while its loop-termination condition becomes True.
Loop-termination condition – the condition used in a repetition statement that enables repetition to continue while the condition is False and that causes repetition to terminate when the condition becomes True
Syntax:
Do Until loop-termination condition
block of statements
Loop Do
block of statements
Loop Until loop-termination condition

16. Do Until..Loop & Do..Loop Until
Example:
Do Until product >= 50
product += 3
Loop Do
product +=3
Loop Until product >= 50
In the Do Until..Loop statement, the loop-termination condition is tested at the beginning of the loop, before the body of the loop is performed.
In Do..Loop Until statement performs the loop-termination condition after the loop body if performed.
Therefore, in a Do..Loop Until statement, the loop body always executes at least once. A Do Until..Loop executes only if its loop-termination condition evaluates to true.

17. Do While..Loop & Do Until..Loop
Dim number As Integer
Do While number < 4 
MsgBox("The number is " & number) 
number = number + 1
Loop
Do Until…Loop
Dim number As Integer
Do Until number > 4
MsgBox("The number is " & number)  
number = number + 1
Loop

18. For…next

19. Counter-controlled Repetition
Four essential elements of counter-controlled repetition:
The name of a control variable (or loop counter) that is used to determine whether the loop continues to iterate
The initial value of the control variable
The increment (or decrement) by which the control variable is modified during each iteration of the loop (that is, each time the loop is performed)
The condition that tests for the final value of the control variable (to determine whether looping should continue)

20. answer = answer + startNumber
For…Next Statement
Optional (depends on the program)
Syntax:
For controlVariable = initialValue To finalValue Step increment
statements
Next
Example
Dim counter As Integer
For counter = 2 To 10 Step 2
MsgBox("The number is " & counter)
Next
Dim answer As Integer
Dim startNumber As Integer
answer = 0
For startNumber = 1 To 4
answer += startNumber
MsgBox(answer)
Next
answer = answer + startNumber

21. For…Next vs. Do While..Loop vs. Do Until..Loop
Dim number As Integer
Do While number < 4 
MsgBox("The number is " & number) 
number = number + 1
Loop
Do Until…Loop
Dim number As Integer
Do Until number > 4
MsgBox("The number is " & number)  
number = number + 1
Loop
For..Next
Dim number As Integer
For number = 1 To 4
MsgBox("The number is " & number)  
Next

22. --- continue to next slide ---