UNIX for Advanced & Expert Users

#include<stdio.h>
#include<sys/stat.h>
#include<sys/types.h>
main()
{
    int flag;
    flag=fork();
    if(flag==0)
    {
        printf("Child \n");    
        printf("Process id= %d\n",getpid());
        printf("Parent id= %d\n",getppid());
    }
    if(flag==-1)
        printf("Error!!!");
    else
    {
        printf("Parent\n");
        printf("Process id= %d\n",getpid());
        printf("Parent id= %d\n",getppid());
        printf("value of flag=%d\n",flag);
    }
}

Parent
Process id= 2332
Parent id= 1855
value of flag=2333
Child 
Process id= 2333
Parent id= 1
Parent
Process id= 2333
Parent id= 1
value of flag=0

main()
{
      int flag;
      flag = fork();

      if( flag == -1 ) // ERROR
      {
            //Error Message
      }
      if ( flag == 0 ) // Child
      {
           //Do child stuff
      }
      if( flag > 0 )
      {
         //Do parent stuff
      }

}