Introduction

Perera Corner Mart, Starlight Cinema and their prices are made up for this unit. Any resemblance to real businesses is a coincidence.

Before writing code, programmers plan the algorithm — the exact steps. Two common ways to write an algorithm down are:

• Flowcharts — diagrams made of standard symbols joined by arrows.
• Pseudocode — structured English that looks a little like code but is not tied to any language.

A clear plan makes the code quicker to write, and mistakes are much easier to spot on paper.

• Describe what an algorithm is and write one in plain steps.
• Name and draw every flowchart symbol.
• Draw flowcharts for sequence, selection (including nested decisions) and loops.
• Read a flowchart, work out its output, and fill in missing symbols.
• Write the same algorithms in pseudocode.
• Trace an algorithm with a trace table to check it works.