Orphan Process
===============
If in a process, the parent process is terminated before the child process, the child process become orphan
- It takes the lowest possible process as its parent
- And its PPID is changed to the PID of its new parent process.
- Mostly the new parent process in init process (PID = 1).
- It is because init adopts the orphan process.
- The child is then terminated normally by the init process.
