While and repeat loops

When to use a while loop?

If you are unsure how many times the loop must execute and also if you are unsure if the loop should repeat at all.

For example: The user enters a password. If the password is not 8 characters long you need to add stars (*) until it is 8 characters long. The user might enter a password that is more than 8 characters and then you do not need to add any stars.

ITC

1. Initialise before the loop
2. Tested in the while condition
3. Changed inside the loop.

The SAME variable

If you fail to do one of these steps your loop will either not execute at all or fall into an infinite loop.

In the example below sPassword is the variable that needs to be initialised before the loop, tested in the while condition and changed inside the loop.

When to use a Repeat loop?

If you are unsure how many times the loop must execute but the loop must execute at least once.

For example: Repeatedly ask the user to enter the answer to a multiple choice question, until they enter an answer from A - D. The user must enter an answer at least once.

CT

1. Changed inside the loop.
2. Tested in the repeat condition

The SAME variable

Failing to do so, will let you fall into an infinite loop. In the example below cAns is the variable that needs to be changed and tested

Practice from past final papers:

1. Temperature will drop by 6.5 °C every 1000m. Allow the user to enter a height and current temperature. Calculate and display the height and temperature until the temperature reaches 0°C or less.
   • Repeat loop: First complete the code to produce the correct output using a Repeat loop.
   • While loop: Now complete the same output but using a While loop
2. Ask the user to enter their current weight. Repeatedly ask the user to enter their goal weight until the goal weight is less than the current weight using a repeat loop. The average person is able to lose 2.25kg per week. Calculate and display in neat columns how the person will lose weight until they have reached their goal weight.
   • Repeat loop: First complete the code to produce the correct output using a Repeat loop.
   • While loop: Now complete the same output but using a While loop
3. An owner of a business would like to see when his initial layout of his business has been paid off. Add two EditBoxes and allow the user to enter the expected income for the first year as well as the initial cost for starting the business.
   • Repeat loop: First complete the code to produce the correct output using a Repeat loop.
   • While loop: Now complete the same output but using a While loop