---
title: "Kernel and its types"
subject: "Embedded System"
chapter: 6
key: "semester_6/embedded_system:kernel-types"
source: https://www.bctengineer.com/q/semester_6/embedded_system/kernel-types
site: BCT Engineering
---

# Kernel and its types

Embedded System · Chapter 6: RTOS

- Asked in: 2073 Bhadra, 3 marks; 2076 Baisakh, 3 marks (asked 2 times)
- Video: [What is kernel | ES | Embedded Systems | Lec-32 |  Bhanu Priya](https://www.youtube.com/watch?v=iocgVBWj7Vk) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/kernel-types
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-6

## Question

Define kernel and explain its types (differentiate between monolithic kernel and micro kernel).

## Short answer

A kernel is the OS core managing CPU, memory, devices, and system calls. Monolithic kernels (Linux) run all services in kernel space for speed but risk crashes. Microkernels (QNX) keep only scheduling, IPC, and basic memory in kernel, running drivers/filesystems in user space for reliability and modularity.

## Answer

The **kernel** is the central part of an operating system. It runs in privileged mode, manages the CPU (scheduling), memory, devices and system calls, and provides the interface between applications and hardware.

#### Types of kernel
1. **Monolithic kernel:** the whole OS (scheduler, memory manager, file system, device drivers, IPC) runs as one large program in kernel space. Examples: Linux, UNIX.
2. **Microkernel:** only the minimum services (basic scheduling, IPC, low-level memory management) stay in the kernel. File systems, drivers and others run as separate servers in user space. Examples: QNX, MINIX, Mach.
3. **Hybrid kernel:** a mix of both (Windows NT, macOS).
4. **Exokernel / nanokernel** are other minimal designs.

| Point | Monolithic kernel | Microkernel |
|---|---|---|
| Size | Large | Small |
| Services in kernel space | All | Only essential (IPC, scheduling, basic memory) |
| Speed | Faster (direct function calls) | Slower (message passing between servers) |
| Reliability | A faulty driver can crash the entire system | More reliable; a failed server does not crash the kernel |
| Modification | Harder; kernel must be rebuilt | Easy; add/replace servers |
| Security | Lower | Higher |
| Examples | Linux, UNIX | QNX, MINIX |

## Check yourself

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

1. What runs in kernel space in a monolithic kernel?
   A. Nothing
   B. Only drivers
   C. The whole OS: scheduler, memory manager, file system, drivers, IPC
   D. Only scheduling and IPC
   Answer: C. Examples: Linux, UNIX. (Key point: Monolithic kernel)

2. What stays in a microkernel?
   A. Nothing
   B. Only minimal services (basic scheduling, IPC, low-level memory); drivers/file systems run as user-space servers
   C. Only the GUI
   D. Everything
   Answer: B. Examples: QNX, MINIX. (Key point: Microkernel)

3. Which comparison is correct?
   A. Monolithic is faster; microkernel is more reliable
   B. Monolithic is more secure
   C. Microkernel is faster; monolithic more reliable
   D. Both identical
   Answer: A. Microkernel message passing is slower, but a failed server does not crash the kernel. (Key point: Speed vs reliability)

## Related in Embedded System

- [User-level versus kernel-level threads](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Auser-vs-kernel-threads) — Embedded System, chapter 6, asked 2×

## Related in other subjects

- [Monolithic vs micro-kernel structure](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Amonolithic-vs-microkernel) — Operating System, chapter 1
- [Microkernel vs monolithic kernel](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Amicrokernel-advantages) — Distributed System, chapter 3