Role of process control block

• At any instance, a process will be having various information associated with it like identifier, state, priority, program counters, memory pointers, accounting information etc. Such information are stored in a data structure called as Process Control block (PCB).
• It is an important tool that helps the OS support multiple processes and provide for multiprocessing.
• It contains sufficient information such that if an interrupt occurs, the process can begin from the point where it left later as if nothing had happened.
• The blocks are read and/or modified by every module in the OS including
  • Scheduling
  • Resource allocation
  • Interrupt processing
  • Performance monitoring and analysis
• It can be said that the process control block defines the state of OS.
• However, there comes the issue of Security; a bug in a single routine say the interrupt handler could damage the PCB which in turn can make it difficult for OS to manage the affected process.
• Changes made to the Process control block (like semantics or design changes) can affect various modules.