Ghosts of Unix past, part 2: Conflated designs

Sorry, of course exec does not create a thread, that would be spawn(), another conflated call. By the way, fork/exec is an example of bad design, see the interaction of fork with pthreads, or the problems of open file descriptors being inherited unwillingly (FD_CLOEXEC). People who write portable software learn to forget about fork and exec very quickly.