The child process must redirect its standard input to come from the down pipe, and its standard output to go to the up pipe. The child must then loop, reading text from its standard input and echoing the text, prepended with "Bounced", to it's standard output. Of course, due to the redirection, the child is actually reading from the down pipe and writing to the up pipe. The code that the child must use for the loop is:
while (fgets(Buffer,STRING_LENGTH,stdin) != NULL) { printf("Bounced %s",Buffer); fflush(stdout); }Note the use of fflush to force the output into the pipe.