My first exposure to assembly language was one of those computers that used self-modifying code for subroutine calls, the Control Data Cyber 6400. It had a spe

My first exposure to assembly language was one of those computers that used self-modifying code for subroutine calls, the Control Data Cyber 6400. It had a special instruction (I think it was called RJ) that replaced the first word of the subroutine with a jump instruction back to the caller. Every function had to start with a special no-op so that it could be replaced, and you returned from a function by jumping back to the beginning.