[jamessu]

Every single program that your computer runs is nothing but a 'pile of bytes' that is carefully set up by your compiler. There is no technical reason that you cannot manually set up said byte piles and execute them, and it is actually not hard at all. (The only 'gotcha' is that some parts of memory are not marked as executable, but this can be changed at runtime or compile-time).

execve does nothing more than swap out which bytes are loaded into the address space of a program (okay, it does some other book-keeping too, but from 100 feet...). It is not necessary for continuing execution outside of what the program has set up at compile-time. In fact, you can dynamically generate code on the fly, as JIT compilers do.