So cool, thanks. As a kid I spent so much time in DEBUG, stepping through DOS's executables, and especially the Interrupt handlers. It's so neat to see the actual source code-- way easier to read and follow. I didn't know it was all written in assembly, from within Debug it sometimes seemed so messy and convoluted that I just assumed more was written in C.
NASA has a paper on how to not poop for days. It's on the Internet. Before space toilets there was only a space bag with finger scissor/scoop holes. It didn't work, poop got everywhere. The paper goes into detail about fecal matter being everywhere after early multi-day missions.
So they figured it out. Their system works -- I've also had my own reasons.