title: Why does fork return 0 for child and return the child's PID for parent and not VICE VERSA?
body: <p>I know that when you call fork() a child process is created and returns a value of 0 to the child process and returns the process ID of the child process to the parent process.  Otherwise, a value of -1 is returned to the parent process, no
  child process is created, and the global variable errno is set to indicate the error. (<a href="https://stackoverflow.com/questions/2562602/how-does-fork-return-for-child-process">How does fork() return for child process</a>)</p>
  
  <p>I know this because my professor said it to me, I can search the net and get the answer etc. But I can't find why it isn't vice versa?</p>
  
  <p>For example parent get 0 and child 12867235. Does anyone have a good explanation on this?</p>
  
  <p>Thansk in advance and excuse my English.</p>