[Kevin Sevcik]

Alright, at the very least, I can state that IF statements won't cost much programming time. The PIC isn't a pipelined processor, so you don't lose time from a branch, so it's not particularly costly. Secondly, doing a calculation in a function/subroutine incurs a fairly significant processing cost versus not doing so. This is mostly because when you call a function, the program has to build a stack saving the current processor state and possibly passing arguments so the instructions in the function can operate in a clean environment. It's not a huge hit, something on the order of 10-20 instructions depending on things, but it does take time.

Edit: X-Istence, computation time can be very very important if you're coding an interrupt service routine or other bits of code where you want things to happen very very quickly. Calling 20 different functions in an interrupt just to keep your code clean isn't a good idea at all. If you want to use functions to keep code clean, I think you can make them inline functions. An inline function basically tells the compiler to take the function and paste it into where your function is called. I'm not positive the C18 compiler supports them out of the box, but I'll look into it.