# Operating System: replace the process's memory space with a new program

What does it mean that "replace the process's memory space with a new program"? So who's memory space will be replaced by whom?

• Re, "...and when we call exec after doing fork..." Just to be perfectly, crystal clear, it is the child process that calls exec(...) to replace its own address space with an image freshly loaded from some executable file. – Solomon Slow Jul 26 '18 at 19:41