Why can't programs be proven?

Question

Why can\'t a computer program be proven just as a mathematical statement can? A mathematical proof is built up on other proofs, which are built up from yet more proofs and

Answer 1

I don't come from a mathematical background, so forgive my ignorance, but what does "to prove a program" mean? What are you proving? The correctness? The correctness is a specification that the program must verify to be "correct". But this specification is decided by a human, and how do you verify that this specification is correct?

To my mind, there are bugs in program because humans have difficulties expressing what they really want. alt text http://www.processdevelopers.com/images/PM_Build_Swing.gif

So what are you proving? Bugs caused by lack of attention?