KS2 Computing: Algorithms and Programming Basics Guide

What is an algorithm?

An algorithm is a precise set of step-by-step instructions for completing a task, followed in order. A recipe or a set of directions are both everyday examples of algorithms.

Sequence, selection and repetition

Sequence means instructions run one after another in order. Selection (using "if" statements) lets a program make a decision and follow different paths. Repetition (using loops) lets a program repeat a set of instructions multiple times without writing them out again.

Debugging

Debugging means finding and fixing errors ("bugs") in a program. A common approach is to run the program step by step, checking what each part actually does compared to what you expected.

Block-based programming

Tools like Scratch let you build programs by snapping together blocks representing instructions, making sequence, selection and repetition easier to see and understand before moving on to text-based code.

Common mistakes

• Confusing an algorithm with the program itself — an algorithm is the plan, the program is the implementation.
• Forgetting a loop needs a clear condition for when to stop.
• Assuming debugging means starting again, rather than testing each part to isolate the problem.