Practice · free · no account

Practise the exact skills your first project needs

14 short exercises in C. You write code, press Run, and see what it does — in this page, with nothing to install and nobody to sign up to. Each one prepares you for a specific project in C & Systems Programming (Zero to the Kernel), the track your free first project comes from. About 92 minutes in total, and you can stop after one.

The code runs in a teaching runtime built for this site: a 32-bit model machine that understands a useful subset of C. It stops on the mistakes a real compiler lets through — reading memory you never wrote to, running off the end of an array, signed overflow — and explains them in words. It is not the compiler you will build your project with, and it does not pretend to be one.