Process

Process

1. Process Model

   • sequential Processes
     • Process is just an instance of executing program, including the current values of the program counters, registers and variables.
     • Program
     • input/output
     • state
   • daemons

2. Process Creation

   • System Initialization
   • Exec of process-creation system call
   • User request to create process
   • Initiation of batch job
   • UNIX
     • fork
       • This call creates an exact clone of the calling process. After fork, the two processes have the same memory image, the same environment strings, and the same open files.
       • execve
   • Windows
     • CreateProcess
       • Handles both process creation and load the correct program in the new process.

3. Process Termination

   • Normal exit
   • Error exit
   • Fatal error
   • Killed
   • UNIX
     • exit
     • kill
   • Windows
     • ExitProcess
     • TerminateProcess

4. Process States

   • Running
     • Running can be Blocked, or it can be Ready (Scheduler).
   • Ready
     • Ready can be Running (Scheduler).
   • Blocked
     • Blocked can be Ready.