There are a few RISC-V software versions out there, but my hope was to write something very simple and accessible. It only has 130 lines of code including comments!

Each loop though main() is effectively a single RISC-V clock tick. So one instruction per tick/loop. At the end of each loop I print out the program counter, the instruction’s name, some registers and decoded opcode parameters, then it waits for a keypress. This way you can single-step through your code and see the internals of the CPU!