How to inform the parent process that I am done

view story

http://stackoverflow.com – This is a very basic question. The parent process will create some shared memory where it will put two integers in there, then it forked a child which will go to the shared memory and compute the sum of them. All this is fine, but how would the child inform the parent that it's done computing the sum? Do I need to create a pipe between the two processes to do this? or waitpid() is sufficient to achieve this? Thank you! (HowTos)