Algorithms: Clear Step-by-Step Instructions (Year 3–4) (Years 3–4) — Computer Science

An algorithm is a set of clear steps, in the right order, that tells someone (or a computer) exactly how to do a job.

An algorithm is a fancy word for a simple idea: a set of steps that tell you how to do a job, one bit at a time, in the right order.

Why this matters: Computers cannot guess. They do exactly what you tell them. If your steps are clear and in the right order, the job works. If not, it goes wrong. Learning to write good steps helps you think clearly about any task.

Steps in the right order

Think about making a jam sandwich. The order of the steps really matters — you cannot put the jam on before you have the bread!

Put these steps in order to make a jam sandwich:

Take two slices of bread
Open the jam jar
Spread jam on one slice
Put the other slice on top

Swap the last two steps and you would spread jam on a slice with nothing under it. Silly! The order is part of the algorithm.

Be exact

A computer follows your words very carefully. If you say "put jam on the bread" but do not say how much or which slice, a computer would not know what to do. Good steps are exact.

Woolly step	Exact step
Get ready	Put on your shoes
Clean up	Put the toys in the box
Go to school	Walk to the front door, then turn left

Everyday algorithms

You follow algorithms all the time without knowing it: brushing your teeth, tidying your room, following a treasure-hunt map. Each one is a set of steps in an order.