C

wait system call

HC: hello from child
Bye
HP: hello from parent
CT: child has terminated
     (or)
HP: hello from parent
HC: hello from child
HC: Bye
CT: child has terminated    // this sentence does 
                            // not print before HC 
                            // because of wait.
Bye

wait system call

// C program to demonstrate working of wait()
#include<stdio.h>
#include<sys/wait.h>
#include<unistd.h>
 
int main()
{
    if (fork()== 0)
        printf("HC: hello from child
");
    else
    {
        printf("HP: hello from parent
");
        wait(NULL);
        printf("CT: child has terminated
");
    }
 
    printf("Bye
");
    return 0;
}