Bug Hunt: Finding and Fixing Code Mistakes

Imagine you are baking a cake. The recipe says: 'Add 2 cups of sugar.' But you read it wrong and add 2 cups of salt. The cake tastes terrible! The recipe was fine — you just followed a wrong step. Computers have the same kind of problem. When someone writes code, they sometimes make a small mistake. The computer follows the wrong instruction and something goes wrong. Can you think of a time when following the wrong instructions caused a problem for you?

A bug is a mistake inside a set of coded instructions. The word 'bug' has been used by programmers for a very long time. When you fix a bug, you are debugging. Bugs come in a few common types: 1. Wrong instruction — the code tells the computer to do the wrong thing. For example, telling a sprite to move 10 steps to the LEFT when it should go RIGHT. 2. Missing instruction — a step has been left out. For example, a program that draws a square forgets one of the four sides. 3. Wrong order — the instructions are in the wrong sequence. For example, a program tells a character to jump BEFORE it starts running, so the jump looks strange. How do you debug? Follow these three steps: • READ the code carefully, line by line. • RUN it in your head (or on screen) and ask: 'What will happen at each step?' • FIX the line that causes the problem, then test again. Debugging is a skill all programmers use — even professional coders debug their work every day.