How to make parent process wait till Completion of Child Process (Joining parent with child process)

How to make the parent process wait till the completion of execution of child process. The following C program makes the parent process to wait till the completion of its child process.

#include<stdio.h>
main()
{

C Program to Show Process ID in Linux

This program is to show the process id (pid) in UNIX or Linx
The system call getpid() returns the process id of current process.

#include<stdio.h>
int main()
{
printf("\n Parent Process ID %d",getppid());
}

Creating A Process in Linux (UNIX) - fork() Example Program

The system call fork() is used to  create a new process in UNIX based operating systems and Linux systems. The fork() system call creates a child process when called from a parent process. Unix will make an exact copy of the parent's address space and give it to the child. Therefore, the parent and child processes have separate address spaces. Here is a C program which uses the fork() system call to create a process during execution. The program is commented well for better understanding.

Program

/*The program (parent process) reads an array from the user.
It sorts it in descending order.