The Basics

What this is

The first step, before a machine and before even a language. A program is a list of instructions the computer follows in order. It can show you things, it can remember things, and it can ask you things. That is the whole of this module, and it is enough to write a program that greets you by name.

We write every idea in plain pseudocode: instructions in ordinary words, for a person to read. No language, no machine, nothing to install. Every real language spells these ideas its own way, and when you pick one up you will find you already know what its instructions are for.

Who it’s for

Anyone starting from nothing. If you have never written a line of code, start here. If you already think in variables and loops, move on to whichever module is new to you.

You do not need a computer to follow this. You need somewhere to think.

The shape

• A program is instructions — the computer does exactly what you wrote, in order.
• One thing after another — the order is part of the program.
• Showing your work — output, and the difference quotation marks make.
• A place to remember — a variable is a named box, and = means put this in.
• Asking the player — input, and a program that gives a different answer for a different person.

Next comes Working It Out, where the computer starts doing arithmetic with what you give it.