Computer science 4th semester Operating system Notes:-
Operating system Notes
💻 Operating System (OS) Notes – CSE 4th Semester | Free PDF, MCQs & Guide
📘 1. Subject Overview – Operating System
An Operating System (OS) is the backbone of every computing system. It acts as an intermediary between the hardware and the user. It manages system resources, coordinates hardware, and ensures a smooth user interface.
Key Functions of an OS:
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Process Management
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Memory Management
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File System Handling
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Device Management
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Security & Protection
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I/O Management
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Multitasking & Multithreading
Operating Systems can be:
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Batch OS
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Time-sharing OS
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Real-Time OS
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Distributed OS
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Mobile OS (Android, iOS)
(Expand this into 100–120 sentences using simple examples, architecture overview, comparisons, and classification.)
🧠 2. Why OS is Important in CSE?
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It builds the foundation for advanced courses like Compiler Design, DBMS, Networking.
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OS helps students understand system-level programming and computer hardware interaction.
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Operating System concepts are key in placement interviews, competitive exams (GATE, JE, SSC Tech), and real-world coding tests.
💡 Every software developer must understand OS internals to build efficient, stable, and secure software systems.
📚 3. Chapter-wise OS Notes Breakdown
🧾 3.1 Introduction to OS
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Definition and purpose
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History and evolution (from punch cards to Android OS)
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OS components (kernel, shell, GUI, CLI)
⚙️ 3.2 Process Management
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Process vs Program
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PCB (Process Control Block)
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Process States and transitions
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Context Switching
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CPU Scheduling Algorithms: FCFS, SJF, Round Robin, Priority
💾 3.3 Memory Management
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RAM, ROM, Cache overview
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Paging, Segmentation
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Virtual memory, Thrashing, Page replacement algorithms (LRU, FIFO, Optimal)
📁 3.4 File System
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File structure and types
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Directory structure (single-level, tree, DAG)
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File allocation methods: contiguous, linked, indexed
🖨️ 3.5 I/O and Device Management
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Buffering, Spooling
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I/O hardware structure
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Device drivers
🔐 3.6 Security & Protection
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User authentication
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Access control list (ACL)
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Threats, malware types, antivirus concepts
🧪 3.7 Deadlocks
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Deadlock conditions
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Resource allocation graph
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Deadlock prevention, avoidance, detection, recovery
(Each topic above should be expanded with clear diagrams, simplified definitions, examples, and practice questions.)
📝 4. Previous Year Question Papers (PYQs) Insight
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Frequently asked topics: CPU Scheduling, Paging, File Allocation
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Repeated short answers: PCB, thrashing, context switching
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Long answer trends: Deadlocks, Memory Allocation, File System Diagrams
💡 Tip: Practice 5 PYQs per week and match with notes for 100% coverage.
📂 5. Downloadable Notes, Charts & PDFs (50+ Sentences)
✅ Handwritten notes
✅ One-pager charts (for revision)
✅ File management diagrams
✅ Algorithm tables (CPU scheduling, page replacement)
✅ Lab files (OS commands, shell script basics)
🧾 Download section on DiplomaYouth provides all PDFs for free.
📎 Visit Now to Download Free PDFs →
🧪 6. Lab Experiments & Practical's
Basic Linux/Unix commands: pwd, ls, chmod, mkdir, ps, etc.
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Shell scripts: Login validation, file handling, arithmetic operations
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Simulations: FCFS, SJF, RR in C/Java
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Virtual Memory simulation
📘 Viva questions included:
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What is a kernel?
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How does a process differ from a thread?
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What is virtual memory?
🎯 7. MCQs and Online Tests
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Topic-wise MCQs for:
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Process Scheduling
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Memory Management
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File Handling
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Deadlocks
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Each test includes 20–50 questions with answer keys and explanations.
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Good for self-assessment before semester and competitive exams.
🧠 Example:
Q: What is the main function of the OS?
A. File Reading B. User Interface C. Process Management D. Web Browsing
✅ Correct Answer: C
🧠 8. OS in Real World – Application and Relevance
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Used in Mobile Phones, ATMs, Servers, IoT Devices
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OS like Linux is used in AI, ML, and Cloud Computing
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Security in OS is vital for banking and defense systems
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Android is based on Linux Kernel
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Windows, macOS, and Linux power almost every laptop and PC
📝 9. Revision Plan & Study Strategy
📅 Weekly Strategy:
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Mon–Wed: Theory reading
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Thu: Practice PYQs
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Fri: MCQs + Test
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Sat: Notes revision
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Sun: Mock viva with friends
🧠 Make flashcards for terms like kernel, page fault, inode, deadlock, etc.
📘 Download CSE 4th Sem OS Notes – Free PDF!
Handwritten notes, MCQs, and PYQs for Operating System
