Operating Systems: notes and questions
For CSE/IT students
Notes for each topic, a formula sheet, practice questions and 52 past GATE questions from 10 papers (2018–2026), 52 of them solved step by step.
- previous-year questions
- 52previous-year questions
- solved step by step
- 52solved step by step
- GATE papers, 2018–2026
- 10GATE papers, 2018–2026
- topics with notes
- 7topics with notes
Foundation
Learn the subject one topic at a time. Each topic has notes, the key formulas and practice questions.
Topic notes and formulas
Notes on every topic, with the key formulas and practice.
Processes, threads and system calls
A system call is the controlled way a user program asks the kernel to act for it, and a process is a program in execution with its own address space and kernel record (the PCB).
5 practice questions
Inter-process communication, concurrency and synchronisation
Concurrent processes that share data can interleave their instructions in many ways, so correctness needs a controlled way to enter critical sections.
5 practice questions
Deadlock: conditions, prevention, avoidance and detection
Deadlock is a state in which every process in a set waits for a resource held by another process in the same set, so none can ever proceed.
5 practice questions
CPU scheduling
CPU scheduling decides which ready process gets the processor next, and for how long.
6 practice questions
Memory management: allocation, paging and segmentation
Memory management decides how the operating system places processes in main memory and turns the addresses a program generates into physical addresses.
5 practice questions
Virtual memory: demand paging and page replacement
Virtual memory lets a process run with only some of its pages in RAM: a page is brought in from disk on demand, and when memory is full a replacement algorithm picks a victim.
5 practice questions
File systems and disk scheduling
A file system decides how files and directories are laid out on disk blocks, how a block is found from a file offset, and how free space is tracked.
5 practice questions
GATE
Past GATE questions on Operating Systems by topic and year, the full papers, practice and the GATE syllabus.
52 questions, by topic and year
How many questions each topic had in the CS papers of each year. This shows what was asked, not what will be asked. We placed each question under a topic ourselves; the exam paper does not label topics.
| Topic | 2018 | 2020 | 2022 | 2023 | 2024 | 2025 | 2026 | Total |
|---|---|---|---|---|---|---|---|---|
| Processes & threads | · | 1 | · | 2 | 4 | 1 | 1 | 9 |
| Synchronisation | 1 | 1 | 1 | 1 | 2 | · | 1 | 7 |
| Deadlock | 2 | · | 1 | · | · | 1 | 2 | 6 |
| CPU scheduling | · | 1 | 1 | 1 | 1 | 2 | 2 | 8 |
| Memory management | · | 1 | 1 | 1 | 3 | 2 | 2 | 10 |
| Virtual memory | 1 | 1 | 1 | 1 | · | 2 | · | 6 |
| File systems & disks | 1 | 1 | 1 | · | · | 1 | 2 | 6 |
Solved papers
GATE CSE question papers with solutions: 2026 Set 1, 2026 Set 2, 2025 Set 1, 2025 Set 2, 2024 Set 1, 2024 Set 2, 2023, 2022, 2020, 2018
GATE 2023 comes from IIT Kanpur's own copy of the paper and its answer key, which numbers the CS questions Q.11 to Q.65. For 2024, 2025 and 2026 both sessions (CS1 and CS2) are included.
36 practice questions
The GATE syllabus for Operating Systems, paper by paper
From the GATE 2027 syllabus PDF: CS Section 8, “Operating System”. Cache memory, interrupts and DMA are listed under Section 3 and are on the Computer Organization and Architecture page.
Show the GATE CS wordingHide the GATE CS wording
System calls, processes, threads, inter‐process communication, concurrency and synchronization. Deadlock. CPU and I/O scheduling. Memory management and virtual memory. File systems.
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Other exams
15 questions on Operating Systems from ISRO's Scientist/Engineer written test (ISRO CS 2025, ISRO CS 2023), by topic. They are not counted in the GATE numbers on this page.
Core jobs for CSE/IT
Skills named in Wadhwani AI's postings for freshers that IAE matched to Operating Systems (listed 19 October 2026).
computer systems
Listed by: Wadhwani AI (organisation): Engineering Trainee (146520000006160157), Delhi (fix-term); Wadhwani AI (organisation): Software Development Engineer - I (146520000005021055), New Delhi (permanent)
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