...that's probably why algorithms are never too big to hold in your head (except crypto, for my head at least :) ), at least once you understand them ...and software tends to be "overgrown" at the interfaces, be it UI or IPC or some networking protocol, not where the "complex" algorithms are anyway (probably because if you can find a mathematically expressible algorithm to do something it doesn't overgrow like a mad bush, even if you add a dozen branches for special cases...)

...and I'm not entirely sure that most algorithms are truly "hermetic" ...maybe in some areas most of them are, dunno...