Operating Systems
Mid-Sem Master
Unit I + Unit II of CIC-305, mapped question by question against the 2023–2025
previous-year papers. Built offline — open index.html and nothing else is needed.
Sources: OS Akash.pdf (primary — Mid-Term Nov 2023, End-Term Jan 2024, Mid-Term Oct 2024, End-Term Dec 2024, Mid-Term Oct 2025, End-Term Dec 2025) and os-akash.pdf (secondary — ETCS-304 papers from 2016, 2017, 2018, 2019 and July 2023). Both books are scanned images with no text layer, so every question was read visually from 200-DPI renders.
How to use this site
30 secondsThe order that works
- Read the coverage matrix below once. It tells you which topics carry the marks.
- Study Unit I, Synchronization and Memory Management in that order, opening every answer.
- Do Numericals with a pen — hide the answer, solve, then compare.
- Use Diagram Bank to learn the 27 drawings that carry the most marks per minute spent.
- Finish with Revision — difference tables, formula sheet, and the 30-minute final pass.
Things worth knowing
- Question wording is verbatim. Where the book's English is confusing it is reproduced as printed, and the answer is rewritten clearly.
- Marks and years appear only where they are legible. Anything unclear is labelled Scan unclear rather than guessed.
- Every numerical was independently re-solved. Where the printed book answer is wrong, the correct value is shown and the printed one sits in an orange Verification note. There are 10 such places.
- Deadlocks, disk scheduling, file systems and Units III–IV are deliberately absent, because they are outside your mid-sem syllabus.
- Ticks, filters and dark mode are saved in this browser and survive a refresh. Use Reset ticks on the Revision page to start over.
- Every page prints cleanly — the sidebar and controls drop out and all answers expand, so you can make a PDF per page.
Study pages
GoUnit I
Introduction, types of OS, OS as resource manager, processes, interrupts, IPC, threads and processor scheduling theory.
Synchronization
Race condition, critical section and its three requirements, software and hardware solutions, semaphores, Dining Philosophers, Producer–Consumer, Sleeping Barber.
Memory Management
Memory organisation and hierarchy, contiguous vs non-contiguous, partition strategies, logical vs physical, paging, TLB, segmentation, virtual memory, demand paging, thrashing, overlays.
Numericals
CPU scheduling with Gantt charts, memory allocation, paging and address translation, page replacement with frame-by-frame traces. All independently re-solved.
Diagram Bank
27 drawn diagrams, each with a “how to draw this in exam” recipe. Process states, threading models, memory hierarchy, paging, fragmentation, page faults, thrashing curve, overlays.
Revision
Most important questions ranked with their PYQ evidence, the difference tables, the formula sheet, common mistakes, the 30-minute final plan and the full syllabus checklist.
Syllabus coverage dashboard
Where the marks arePriority is assigned from recency and repetition in the papers, not from a guessed probability. Very high means the topic comes back repeatedly across the 2023–2025 papers — page replacement and CPU-scheduling numericals appear in all six. High means it was asked once or twice recently. Medium means only the older papers ask it. Cover for safety means it is named in your syllabus but asked in neither book.
PYQ coverage matrix — Unit I
| Unit | Topic | Recent PYQ | Old PYQ | Priority |
|---|---|---|---|---|
| I | What is an Operating System | Yes — Dec-2025, Jan-2024 | Yes | Very high |
| I | Simple batch systems | Yes — Jan-2024, Oct-2024 | Yes — May-June 2017 | High |
| I | Multi-programmed batch systems | Yes — Nov-2023, Oct-2024, Dec-2024 | Yes — May-2016 | Very high |
| I | Time-sharing systems | Yes — 4 papers | Yes — Feb-2018 | Very high |
| I | Personal-computer systems | None | None | Cover for safety |
| I | Parallel systems | None | Yes — May-2016, Jun-2019 | Medium |
| I | Distributed systems | Partly — inside Jan-2024 IPC | Yes — May-2016, Jun-2019 | High |
| I | Real-time systems | Yes — 4 papers | Yes — Feb-2019 | Very high |
| I | OS as a resource manager | Yes — 3 papers | Yes — May-June 2017 | Very high |
| I | Processes — introduction | Yes — 3 papers | Yes — Feb-2017 | Very high |
| I | Process states | Yes — Nov-2023, Oct-2025 | Yes — May-2016, Feb-2017 | Very high |
| I | Process management / PCB | Yes — Jan-2024, Oct-2024, Oct-2025 | Yes — Jul-2023, Jul-2016 | Very high |
| I | Interrupts | None standalone | None | Cover for safety |
| I | Interprocess communication | Yes — Jan-2024 (7.5) | Yes — May-2016, May-June 2018 | Very high |
| I | Threads — introduction | Yes — 4 papers | Yes — Jul-2023, Feb-2018 | Very high |
| I | Thread states | Yes — Jan-2024 | Yes — Feb-2018 | High |
| I | Thread operation / ULT vs KLT | Yes — Dec-2024, Dec-2025 | Yes — Jul-2023, Jun-2019 | Very high |
| I | Threading models | None | Partly — May-2016 (M:1 vs 1:1 only) | Medium |
| I | Scheduling levels | Yes — 3 papers | Yes — Feb-2017, May-2016 | Very high |
| I | Preemptive vs non-preemptive | Yes — 3 papers | Yes — Feb-2017 | Very high |
| I | Priorities | Yes — Dec-2025 | Yes — May-June 2018 | High |
| I | Scheduling objectives | Yes — Jan-2024, Dec-2024 | Yes — Feb-2017 | High |
| I | Scheduling criteria | Yes — Jan-2024, Dec-2025 | Yes — 2018, 2017, 2016 | Very high |
| I | Scheduling algorithms | Yes — all 6 papers | Yes — all years | Very high |
| I | Demand scheduling | Yes — Jan-2024 | None | High |
| I | Real-time scheduling | Yes — Jan-2024 | Yes — Jun-2019 | High |
PYQ coverage matrix — Unit II
| Unit | Topic | Recent PYQ | Old PYQ | Priority |
|---|---|---|---|---|
| II | Mutual exclusion | Yes — Jan-2024 (7.5) | Yes — May-June 2017 | Very high |
| II | Software solutions (Peterson, Dekker, Bakery) | Yes — Oct-2024 Bakery | Yes — 2019, 2017, 2016 | Very high |
| II | Hardware solutions (Test-and-Set, Swap) | Yes — Jan-2024 | Swap only, 2017 | Very high |
| II | Semaphores | Yes — 4 papers | Yes — 2018, 2016 | Very high |
| II | Critical section problem | Yes — 3 papers | Yes — Feb-2019, Jun-2019 | Very high |
| II | Dining philosophers | Yes — 4 papers | Yes — 2018, 2016, 2023 | Very high |
| II | Barber shop (Sleeping Barber) | None | None | Cover for safety |
| II | Race condition | Yes — Dec-2024 | Yes — 2023, 2016, 2019 | High |
| II | Producer–Consumer | Yes — inside Jan-2024 IPC | Yes — May-June 2018 | High |
| II | Memory organization | Yes — Jan-2024 caching/buffering | Yes — May-June 2018 | High |
| II | Memory hierarchy | None | Yes — May-June 2017 | Medium |
| II | Memory management strategies | Partly — Oct-2025 | Yes — May-2016, May-June 2018 | High |
| II | Contiguous vs non-contiguous | Partly — Oct-2025 | Yes — May-2016 | High |
| II | Partition management (first/best/worst fit) | Yes — Dec-2025 (6) | Yes — 2023, 2017, 2018, 2016 | Very high |
| II | Internal vs external fragmentation | Yes — 3 papers | Yes — Feb-2018, May-June 2018 | Very high |
| II | Logical vs physical address space | Yes — Nov-2023, Dec-2025 | Yes — 2016, 2023, 2018 | Very high |
| II | Swapping | None | None | Cover for safety |
| II | Paging / page table / TLB | Yes — 4 papers | Yes — 2023, 2016, 2019 | Very high |
| II | Segmentation | Yes — 3 papers | Yes — May-June 2018 | Very high |
| II | Segmentation with paging | Yes — Jan-2024 (7) | Yes — 2016, 2018, 2019 | Very high |
| II | Virtual memory | Yes — 3 papers | Yes — Feb-2019 | Very high |
| II | Demand paging | Yes — Dec-2025 | Yes — Jun-2019 | Very high |
| II | Page replacement | Yes — all 6 papers | Yes — all years | Very high |
| II | Page-replacement algorithms | Yes — FIFO, LRU, Optimal, MFU | Yes — plus Belady, MFU | Very high |
| II | Performance of demand paging | Yes — Dec-2024 TLB | Yes — 2016, 2019 | High |
| II | Thrashing | Yes — Nov-2023, Oct-2025 | Yes — 2019, 2018, 2017, 2016 | Very high |
| II | Demand segmentation | None | None | Cover for safety |
| II | Overlay concepts | None | Yes — Feb-2019 | Medium |
Topic priority matrix
Study order| Tier | Topics | Why it sits here |
|---|---|---|
| Very high | Page-replacement numericals · CPU-scheduling numericals · internal vs external fragmentation · paging vs segmentation · segmentation with paging · critical-section requirements · Dining Philosophers · semaphores and busy waiting · thrashing · process states and PCB · the three schedulers · preemptive vs non-preemptive · OS as resource manager · types of OS · real-time systems · process vs thread and ULT/KLT · IPC · logical vs physical address · scheduling criteria · mutual exclusion · partition allocation strategies | Each appears in four or more of the six 2023–2025 papers, and most repeat in the older papers too. Page replacement and CPU-scheduling numericals appear in every paper. |
| High | Bakery algorithm · race condition · Producer–Consumer · caching vs buffering · demand paging · TLB and effective access time · convoy effect · page size as a power of two · demand and real-time scheduling · scheduling objectives · memory management strategies · queueing diagram · simple batch systems · distributed systems | Asked once or twice in the recent set. Usually a 2–5 mark part-question rather than a full one. |
| Medium | Parallel systems · threading models · memory hierarchy · overlays · multiprocessing detail | No recent paper asks them; the older ETCS-304 papers do. Cheap marks if you spend twenty minutes on each. |
| Cover for safety | Sleeping Barber · Test-and-Set explicitly · Peterson's and Dekker's · swapping · demand segmentation · personal-computer systems · interrupts · many-to-many model | Named in your syllabus but asked in neither book. One paragraph each is the right amount of effort — do not lose sleep over them, but do not walk in blank either. |