1. What is a Process?

A process is a program in execution, including the program code, data, and resources like CPU, memory, and files.

2. Process States

  1. New – Process is being created.

  2. Ready – Waiting to be assigned CPU.

  3. Running – Currently executing.

  4. Waiting/Blocked – Waiting for an event (I/O completion).

  5. Terminated – Execution finished.

3. Process Control Block (PCB)

A PCB is a data structure maintained by the OS for each process, containing:

  • Process ID (PID)

  • Process state

  • CPU registers

  • Program counter

  • Memory management info

  • I/O status

4. Context Switching

Process of saving the state of the current process and loading the state of another process.
🔹 Occurs during multitasking and CPU scheduling.

5. Threads

  • Thread = lightweight process.

  • Share same code, data, and OS resources, but have independent registers & stack.

  • Multithreading improves CPU utilization.

6. Types of Scheduling

  • Preemptive – CPU can be taken from a process before completion (e.g., Round Robin).

  • Non-Preemptive – CPU given until process finishes or blocks (e.g., FCFS, SJF).

7. GATE Important Points

  • Process is dynamic; program is static.

  • PCB is essential for context switching.

  • Thread creation is faster than process creation.

Day 2 – Practice Questions (with Answers)

Q1. Define process in one line.

Answer: A process is a program in execution along with its resources and current state.

Q2. Name the 5 classic process states.

Answer: New, Ready, Running, Waiting/Blocked, Terminated.

Q3. What does a PCB store?

Answer: PID, process state, CPU registers, program counter, memory info, I/O status.

Q4. What is context switching?

Answer: Switching CPU from one process to another by saving and restoring process states.

Q5. Which is faster: process creation or thread creation?

Answer: Thread creation.

Q6. Which scheduling type allows interruption?

Answer: Preemptive Scheduling.

Q7. FCFS scheduling is preemptive or non-preemptive?

Answer: Non-preemptive.

Q8. In which state is a process when waiting for I/O completion?

Answer: Waiting/Blocked state.

Q9. What is a lightweight process?

Answer: Thread.

Q10. Which data structure is most important for process management?

Answer: Process Control Block (PCB).