Repetition StatementsRepeating an Action

A specified number of timesWhile a Condition is TrueUntil a Condition is True

3 Requirements for a Successful LoopInitialize a Loop Control VariableTest the Loop Control Variable against an

Exit ConditionUpdate the Loop Control Variable

Must be approaching exit criteria

Counted / For LoopSpecified Number of TimesSyntax:

For loopVariable = start To End [Step StepValue]

StatementsNext [loopVariable]

[ ] means optional

ExampleFor counter = 1 to 10 Step 1

msgBox (“The current number is: “ & counter)

Next

Try ItWrite a program that uses a counted/for loop

to read in a 5 numbers (using an inputBox) and display their average in a label.

Try it AgainWrite a program using a counted/for loop

that will add the numbers from 1 – 50 and display the output in a label.

Write a program using a counted/for loop that will add the odd numbers from 1 – 50 and display the output in a label.

While LoopsContinue Looping While a Condition is TrueSyntax:

Do While (condition statement)statements

Loop

Pre-Test LoopIn a While Loop the Loop Exit condition is

tested before the program enters the loopPre-Test LoopIf Condition is False, the Loop code may never

execute Minimum number of executions of loop is 0

ExampleDo While (number <=10)

MsgBox (“The current number is: “ & number)

number = number + 1Loop

Try ItWrite a program to require the user to enter

a correct password (“Friday”). When they enter the correct password the program will display “Have a Great Week-end”.

Try it AgainWrite a program that will calculate the

number of years it will take for a given input deposit amount to increase to a million dollars at 6% annual interest.

Test $100,000 should take 40 years

Do Until LoopContinues Executing Until a Condition is

True

Syntax

Dostatements

Loop Until (condition)

Post Test LoopIn a Do..Until Loop the loop checks Exit

Condition After the Loop ExecutesPost Test LoopMinimum Number of Executions of Loop is 1

ExampleDim strPassword

DostrPassword = InputBox (“Enter Password”)

Loop Until (strPassword = “Friday”)

Try ItNote: All Loops can be written as Do While

LoopsPractice this example using a D0 Until Loop

Write a program that reads in a list of positive integers from the user until the user enters the value of -1 (a sentinel value – exit value). At that time the program should display the largest value in the input list.

Review of Loops3 Requirements for Successful Loop

Initialize a Loop Control VariableTest the Loop Control Variable against an Exit

ConditionUpdate the Loop Control Variables

3 Types of LoopsCounted Loop – executes a specific number of

timesWhile Loop – Pre-test loopDo Until Loop – Post-test loop

ALL Loops can be written as While Loops