Repetition Statements Repeating an Action A specified number of times While a Condition is True Until a Condition is True

3 Requirements for a Successful Loop Initialize a Loop Control Variable Test the Loop Control Variable against an Exit Condition Update the Loop Control Variable Must be approaching exit criteria

Counted / For Loop Specified Number of Times Syntax: For loopVariable = start To End [Step StepValue] Statements Next [loopVariable] [ ] means optional

Example For counter = 1 to 10 Step 1 msgBox (“The current number is: “ & counter) Next

Try It Write 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 Again Write 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 Loops Continue Looping While a Condition is True Syntax: Do While (condition statement) statements Loop

Pre-Test Loop In a While Loop the Loop Exit condition is tested before the program enters the loop Pre-Test Loop If Condition is False, the Loop code may never execute Minimum number of executions of loop is 0

Example Do While (number <=10) MsgBox (“The current number is: “ & number) number = number + 1 Loop

Try It Write 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 Again Write 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 Loop Continues Executing Until a Condition is True Syntax Do statements Loop Until (condition)

Post Test Loop In a Do..Until Loop the loop checks Exit Condition After the Loop Executes Post Test Loop Minimum Number of Executions of Loop is 1

Example Dim strPassword Do strPassword = InputBox (“Enter Password”) Loop Until (strPassword = “Friday”)

Try It Note: All Loops can be written as Do While Loops Practice 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 Loops 3 Requirements for Successful Loop Initialize a Loop Control Variable Test the Loop Control Variable against an Exit Condition Update the Loop Control Variables 3 Types of Loops Counted Loop – executes a specific number of times While Loop – Pre-test loop Do Until Loop – Post-test loop ALL Loops can be written as While Loops