babbage% gcc -o fork-2 fork-2.c && fork-2 
The child process is active.
The parent process is active.
The string received is 'Your parent is calling'
babbage% fork-2
The parent process is active.
babbage% The child process is active.
The string received is 'Your parent is calling'
fork-2
The parent process is active.
babbage% The child process is active.
The string received is 'Your parent is calling'