When studying protocols, you can compare apples-to-apples because the protocol has to work the same way by design, but the implementation can vary. With compilers, you're getting a look into programming in its maximally symbolic form - and every strategy a compiler uses is one you can directly apply to abstract your own code. And commercial video games have another mode of apples-to-apples in that the original release - the dirty, meets-deadline stuff - often can be compared with fan remakes and patches, which have the luxury of an exact specification and no deadlines. To actually ship in industry, you have to accept and know good dirty code hacks, but it's worth comparing them to their counterparts.
* Protocol implementations(e.g. TCP, HTTP, MIDI)
* Smaller compilers(PUC-Rio Lua, Forth-80)
* Commercial video game sources [0]
When studying protocols, you can compare apples-to-apples because the protocol has to work the same way by design, but the implementation can vary. With compilers, you're getting a look into programming in its maximally symbolic form - and every strategy a compiler uses is one you can directly apply to abstract your own code. And commercial video games have another mode of apples-to-apples in that the original release - the dirty, meets-deadline stuff - often can be compared with fan remakes and patches, which have the luxury of an exact specification and no deadlines. To actually ship in industry, you have to accept and know good dirty code hacks, but it's worth comparing them to their counterparts.
[0] https://en.m.wikipedia.org/wiki/List_of_commercial_video_gam...