---
title: "Short note: Distributed OS"
subject: "Distributed System"
chapter: 3
key: "semester_7/distributed_system:dos-note"
source: https://www.bctengineer.com/q/semester_7/distributed_system/dos-note
site: BCT Engineering
---

# Short note: Distributed OS

Distributed System · Chapter 3: Operating System Support

- Asked in: 2072 Chaitra, 4 marks
- Video: [Distributed Systems | OS | Lec-06 | Bhanu Priya](https://www.youtube.com/watch?v=fM7z0X08mzo) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/distributed_system/dos-note
- Whole chapter: https://www.bctengineer.com/md/semester_7/distributed_system/chapter-3

## Question

Write a short note on Distributed OS.

## Short answer

A distributed operating system manages networked computers as a single machine, providing transparency, global resource management, inter-process communication via RPC, distributed file system, and fault tolerance. It is rarely used directly; instead its functions are implemented as middleware over existing network OS.

## Answer

A **distributed operating system (DOS)** manages a group of independent, networked computers and presents them to users as a single computer. It hides the existence of many machines and controls their resources as one pool.

**Characteristics**
- **Transparency:** location, migration, replication, concurrency and failure.
- **Global resource management:** global scheduling, load balancing and process migration.
- **Inter-process communication:** message passing, RPC and group communication between nodes.
- **Distributed file system** with a common name space.
- **Fault tolerance** and reliability through replication and recovery.
- **Scalability** and flexibility, often built on a **microkernel**.

**Differences from a network OS:** the users in a DOS do not know on which machine their programs run, while in a NOS each machine has its own OS and users log in to a particular one.

**Examples:** Amoeba, Mach, Sprite, V-system, Plan 9.

**Problems:** needs same OS on all nodes, poor scalability, complex design; so in practice the idea is realised as middleware over network operating systems.

## Check yourself

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

1. What does a distributed OS present to its users?
   A. Many separate computers
   B. A single computer
   C. Only a file server
   D. A set of unrelated OSs
   Answer: B. A DOS manages networked computers as one pool and hides the existence of many machines. (Key point: DOS definition)

2. What is the main difference seen by the user between DOS and NOS?
   A. In a NOS users do not know where programs run
   B. In a DOS users log in to a particular machine
   C. In a DOS users do not know which machine runs their programs
   D. There is no difference
   Answer: C. In a NOS each machine has its own OS and users log in to one; a DOS hides this. (Key point: DOS vs NOS)

3. Which is a problem of a distributed OS?
   A. It supports many different OSs
   B. It needs the same OS on all nodes and scales poorly
   C. It has no transparency
   D. It is simple to design
   Answer: B. These problems are why the idea is realised as middleware over network OSs. (Key point: DOS problems)

## Related in Distributed System

- [Context switching; distributed vs network OS](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Acontext-switch-dos) — Distributed System, chapter 3
- [Network OS vs distributed OS](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Anos-vs-dos-diff) — Distributed System, chapter 3
- [JINI goals, CORBA services, OS support](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Aos-support-jini-corba) — Distributed System, chapter 3

## Related in other subjects

- [Multiprogramming, multiprocessing, distributed OS](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Amultiprog-multiproc-distributed-os) — Operating System, chapter 1