[C-CODE]How to fork process in unix?

/*Code open-sourced by http://codejar-lab.in
This is only for study purpose only and if you found any error use own logic to correct it so dont comment error.
*/
#include<stdio.h>
int main()
{
 int PId;
 PId = fork();
 if ( PId == 0 )
 {
  printf("Child Here.....\n");
  sleep(20);
  printf("   Parent Id   :  %d\n",getppid());
  printf("   My Id       :  %d\n",getpid());
 }
 else
 {
  printf("Parent Here.....\n");
  printf("   My Child     :  %d\n",PId);
  printf("   My Id        :  %d\n",getpid());
  printf("   My Parent    :  %d\n",getppid());
 }
}

How to run it? 
$gcc file.c
$./a.out