It's trivial to say that a program describes its behavior exactly (so it's its own spec). But the whole point of a spec is to describe how a program should beh

It's trivial to say that a program describes its behavior exactly (so it's its own spec). But the whole point of a spec is to describe how a program should behave before writing it. Also you usually want some verification that the program matches the spec. When the program IS the spec what do you match?