What is absolute code and why is it known at compile time?

Question

While studying for my Operating System Concepts final, I stumbled across

Compile time: If memory location knows, **absolute code** can be generated;
must recompile code if starting location changes

And the example gives for absolute code is the interrupt vector table. I was wondering what exactly that statement means and why is the interrupt vector table known at compile time?

Answer 1

It means code that loads at a known, fixed memory address. Since that address is fixed, jumps can be compiled to point directly to their target memory addresses, with no need to use relative jump instructions or fixup anything at load time.