KS3 Computing/Iteration

Iteration
Iteration (looping) is a way of repeating a specific chunk of code several times. It might be a specific number of times, e.g. 10, or it might be until a certain condition is met. For example, if you want to repeat a phrase 3 times, you could do:

This is called a for loop and would output the following: Time for holidays! Time for holidays! Time for holidays!

Types of loops
The different types of loops include those that:
 * Repeat n times - where n is the number of times the code is executed
 * Repeat until - where the code is repeated until a certain condition is true/false
 * Repeat forever - where the code is repeated continuously until the end of the program

Loops in Python include: for while

Loops in Scratch include: repeat forever

Introducing the concept of looping
It is a good idea to let younger students write long sections of code first, then ask them how they might reduce the number of lines of code / make their code more 'efficient' (answer = by introducing a loop!).

A simple example of this would be asking them to print out the 3 times tables. At first they would manually print out all parts, e.g. print("1x3=3") written out 12 times. Once they have done this, show them how a loop can get the program to do all the hard work! Example code in Python would be:

Here is an example of introducing loops in Scratch