why putting \n alters the order of execution

while I am trying to code in c for zombie process simulation ,I am getting alteration in output due to putting of \n in printf statements:

code1:

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

 if(id>0)
  {
     printf("Parent will sleep");//pf1//
     sleep(5);
     //system("ps -u");
  }
 if(id==0)
     printf("I am child");//pf2//
}

output:

I am childParent will sleep

but while putting \n in pf1 or pf2 the order of execution of statements changes.what is the reason behind \n altering the order ?