The program uses fork() to create a child process from the parent process. fork() returns 0 to the child process and the new process ID to the parent. A switch statement checks the return value of fork() and causes the child process to immediately exit while the parent process continues on. The parent process then prints "XYZZY", so the magic word is printed by the parent process alone.

1. Consider the following valid C program:
Which process(es) print(s) out the magic word, XYZZY? Choose one of the following:
1. Both the parent and child processes
Solution
/* #include statements */
main()
{
pid_t spawnpid = fork();Â Â //Creates a new process with the fork(), and the return value is
assigned to spawnpid.
//The fork returns a negative value, if the child process creation fails.
//The fork returns a positive value, if the child process creation is successful.
//The fork returns a zero, to the child process.
//If the process creation is successful, all the instructions from hereafter will be executed by both
the processes.
switch (spawnpid)
{
case -1: exit(1); break;Â Â //The parent process spawnpid is a positive value, and the child
process spawnpid is 0.
case 0: exit(0); break;Â Â //The child process spawnpid is 0, and therefore, will exit at this
point.
default: break;Â Â Â Â Â Â Â Â //The parent process spawnpid is neither negative nor zero,
so this will come out of the switch.
}
printf("XYZZY ");Â Â Â Â Â Â Â Â //Therefore, the parent process executes this statement,
after coming out of the switch.
}
And therefore, the answer is: 3. The parent process.