Step by Step: How Computers Follow Instructions

Imagine you want to make a bowl of cereal. What do you do first — eat the cereal, pour the milk, or open the box? The order matters! If you pour the milk before you open the box, something goes wrong. Computers have exactly the same problem. They follow instructions one at a time, in order. If the order is wrong, things go wrong.

In coding, a sequence is a list of instructions that run one after another, in a set order. The computer reads the first instruction, carries it out, then moves to the next one, and so on. It never skips a step and never does two steps at the same time. Think of a sequence like a recipe. A recipe tells a cook exactly what to do and in what order. If the cook bakes the cake before mixing the ingredients, the cake will not turn out right. A computer is the same — it does whatever you tell it, in exactly the order you write it. Here is a simple sequence that tells a robot to move to a water fountain and drink: Step 1 — Stand up. Step 2 — Walk to the fountain. Step 3 — Press the button. Step 4 — Drink the water. Step 5 — Walk back to your seat. Every step must be in the right place. If Step 3 came before Step 2, the robot would press a button that is far away — and nothing would happen! In block-based coding tools (like Scratch), you stack coloured blocks on top of each other. The computer runs the top block first, then the next, then the next — always top to bottom. That stack of blocks is your sequence.