In any modern operating system, the Process Control Block (PCB) is the fundamental data structure used by the OS to manage processes. For a 10-mark answer, structure your response as follows:

Definition and Role of the PCB

• The PCB is a kernel data structure that contains all the information about a single process.
• Role:
  1. Identification: Uniquely identifies the process to the OS (via Process ID).
  2. State Maintenance: Tracks the current state (New, Ready, Running, Waiting, Terminated).
  3. Context Switching: Stores CPU context (registers, program counter) so the OS can suspend and resume processes.
  4. Resource Management: Keeps track of allocated resources (memory, I/O devices, files).
  5. Scheduling & Accounting: Holds scheduling parameters (priority, scheduling queues) and accounting data (CPU time used, user ID).

Advantages of the PCB

1. Efficient Context Switching
   • All required CPU context is stored/restored in one place.
2. Isolation & Protection
   • Each process’s data is encapsulated; prevents accidental interference.
3. Resource Tracking
   • Simplifies management of memory, files, and devices per process.
4. Fair Scheduling & Accounting
   • Enables precise tracking of CPU usage for scheduling and billing.

Disadvantages of the PCB

1. Memory Overhead
   • Each PCB consumes kernel memory; many processes can tax OS memory.
2. Complexity
   • Maintaining and updating PCBs (especially in multiprocessor systems) adds implementation complexity.
3. Overhead in Context Switches
   • Saving/restoring large PCBs during context switches can degrade performance.