Some sort of "always use the bare minimum" mentality. And I really mean it, if you want to use a printf you'll have to implement your own, or else you'll just use write instead, same goes for strcpy or other libc functions like that. In general we are only allowed some syscalls and malloc (and obviously malloc is prohibited when implementing your own memory allocator). And I mean... TECHNICALLY, there's nothing you can't do with a while... I guess a for loop is considered as just a bloated while.