That's what we did on the old swap based systems, on modern paged systems we don't read pages in untill there is a page fault, to do that efficiently we need to

That's what we did on the old swap based systems, on modern paged systems we don't read pages in untill there is a page fault, to do that efficiently we need to align page boundaries with disk block boundaries - elf (and coff before it) allowed you to do this while a.out doesn't