Foundations
Structure
Lists, jobs with names, jobs that take a value and hand one back, and the one skill that separates getting it done from getting stuck.
Begin — Unit 01 →What this is
Programs grow. A box that holds one value is not enough for a row of enemies, and a job that turns up in five places should be written once. This module is about giving a program shape so it stays readable as it gets bigger.
It ends with the most useful unit on the whole shelf: what to do when a program does the wrong thing, by looking at what it did rather than guessing.
Who it’s for
Anyone who has finished Repeating. A list and a loop belong together, and the debugging unit traces a loop by hand.
The shape
- A box that holds many — lists, reaching into them, and walking along them.
- A job with a name — write it once, call it wherever you need it, and leave a note.
- Telling a job what to work on — a job that takes a value and hands one back.
- When it’s wrong — look, narrow down, read; make the program show its working; suspect your own code first.
That is the end of the programming shelf. From here you pick a language to say these ideas in: Meet BASIC on a machine you like the look of. Or head for the metal, starting with Counting in Twos.