Ah, I'll give you the best answer ever in computing:

It depends.

Explicit paths for everything in your program sounds like overkill, since you have to maintain the paths and may end up with big headaches if you ever move stuff around.

Personally, I'd organize the files so I wouldn't have to do a lot of chdir'ing. Then set the path once and go about the rest of the business. But I don't want to make a blanket statement about how to organize files and i/o without knowing a whole lot more about what you're doing. (Not that I want to know -- I've got enough problems of my own. ;-)

HTH