checking process status using C function

Is there a unix C function that I can use to check the status of any
(non-child) process  on the system  if I know the process id and/or process name without using something  like system("ps") and checking the result.  wait/waitpid only works for child processes.

I believe there are win32 api that I can use to check the instance
of self running on the system and checking the status of other
process (WaitForSingleObject).

Thanks.

-clint