MAME is a really impressive piece of software. It emulates tens of thousands of machines and goes into painstaking detail to get things right.

One of the coolest aspects of their codebase is the ASCII-art diagrams of arcade circuit boards[1], dip switches, and memory maps. These are used to help document each machine driver.

[1] https://github.com/mamedev/mame/blob/f548e02647523b87b269ff7...