O0 to Hero

C and assembly side by side

O0 to Hero is a programming-learning game for PC, built around seeing how C becomes x86-64 assembly. You write a line of C, then read the matching output from the real gcc compiler beside it. Editing the C updates the assembly. The compiler runs at -O0, with optimization off, so variables keep their own stack slots and the resulting assembly follows the code in a more literal way.

Lessons start with what a program is, how source code becomes something a machine runs, and why memory is divided into numbered bytes. From there, the course teaches C, with each new idea read back through its assembly output. Real checks grade your code, and a failed submission costs nothing. Quiz cards you miss return until you answer them correctly.