[SOLVED] 0 = false, 1 = true?

So I think I've got this right. As above 0 = false, 1 = true. Standard boolean with C. My problem is I'm getting true, or 0 results from things that are true. Shouldn't they be 1? I found it by accident while playing with the access() function. It returns 0 when the file exists, otherwise 1. Yet if 1 is true...

So do I have it wrong or have I been taught wrong?

*EDIT* or is there an inconsistency problem in the standard libs?