---
title: "What is process; process vs thread"
subject: "Operating System"
chapter: 2
key: "semester_6/operating_system:process-vs-thread-define"
source: https://www.bctengineer.com/q/semester_6/operating_system/process-vs-thread-define
site: BCT Engineering
---

# What is process; process vs thread

Operating System · Chapter 2: Process Management

- Asked in: 2072 Magh, 1+3 marks
- Video: [Process Management (Processes and Threads)](https://www.youtube.com/watch?v=OrM7nZcxXZU) — Neso Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/operating_system/process-vs-thread-define
- Whole chapter: https://www.bctengineer.com/md/semester_6/operating_system/chapter-2

## Question

What is a process? Differentiate between process and thread.

## Short answer

A process is a program in execution with its own resources and address space. Threads are lightweight execution units within a process, sharing the address space and resources, which makes creation and context switching cheaper than for processes.

## Answer

A **process** is a program in execution: an active entity that includes the program code, program counter, registers, stack, data and the resources (open files, address space) allocated to it. The OS keeps its details in a process control block.

#### Process vs thread

A **thread** is a lightweight process: the basic unit of CPU utilization within a process.

| Basis | Process | Thread |
|---|---|---|
| Definition | Program in execution, a resource owner | Unit of execution inside a process |
| Address space | Own address space | Shares the address space of its process |
| Resources | Own files, memory, I/O | Shares them; has only its own stack, registers and PC |
| Creation and switching cost | High | Low |
| Communication | Through IPC (slow) | Through shared memory (fast) |
| Independence | Independent, protected | Dependent; one thread can affect others |
| Example | Two separate programs, such as a browser and a text editor | The typing, spell-check and auto-save threads inside one word processor |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is a process?
   A. A passive file of instructions on disk
   B. A program in execution with code, program counter, registers, stack, data and allocated resources
   C. A lightweight unit inside a thread
   D. A hardware interrupt
   Answer: B. A process is an active entity: a program in execution, whose details the OS keeps in a PCB. (Key point: Process definition)

2. How do processes and threads typically communicate?
   A. Processes through shared memory (fast); threads through IPC (slow)
   B. Processes through IPC (slow); threads through shared memory (fast)
   C. Both only through files
   D. Neither can communicate
   Answer: B. Processes have separate address spaces so need IPC; threads share the address space and use it directly. (Key point: Communication difference)

3. Which statement is correct?
   A. Thread creation and switching cost is high, process is low
   B. Processes are independent and protected, while one thread can affect others
   C. Threads have their own address space
   D. Threads own separate open files
   Answer: B. Processes are isolated; threads share everything but stack, registers and PC, so one can affect the others, and they are cheap to create and switch. (Key point: Cost and independence)

## Related in Operating System

- [Process vs thread; multithreading advantages](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Aprocess-thread-multithreading) — Operating System, chapter 2
- [Process vs thread; context switching](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Athread-context-switching) — Operating System, chapter 2
- [Process vs thread; user and kernel threads](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Aprocess-vs-thread-user-kernel-threads) — Operating System, chapter 2
- [Preemptive vs non-preemptive; process states](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Apreemptive-nonpreemptive-process-states) — Operating System, chapter 2

## Related in other subjects

- [Process vs thread and task states](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aprocess-thread-and-task-states) — Embedded System, chapter 6
- [Process versus thread differences](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aprocess-vs-thread) — Embedded System, chapter 6, asked 4×
- [Instruction, thread, process level parallelism](https://www.bctengineer.com/question.md?key=semester_4%2Fmicroprocessor%3Ainstruction-thread-process-parallelism) — Microprocessor, chapter 6
- [Process vs threads; importance in DS](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Aprocess-vs-thread) — Distributed System, chapter 3, asked 3×