Complete OS handwritten notes with simple explanations
An Operating System (OS) is the core software that manages a computer's hardware and provides a platform for application programs to run. It acts as an interface between the user and the hardware, handling tasks like process scheduling, memory allocation, file management, and input/output operations. Understanding OS concepts is essential for every Computer Science and IT student, as it forms the foundation for subjects like Distributed Systems, Computer Networks, and System Design.
Our handwritten OS notes are designed to simplify complex topics such as process scheduling, deadlocks, memory management, paging, and disk scheduling algorithms — with clear diagrams and solved examples that match university exam patterns (AKTU, RGPV, GGSIPU, and more).
CPU scheduling, memory management, and deadlock handling are among the highest-weightage topics in most university OS exams. Numerical problems on scheduling algorithms (FCFS, SJF, Round Robin) and page replacement techniques (FIFO, LRU, Optimal) are almost guaranteed to appear in semester papers, so understanding both the theory and practical problem-solving is important.
Learn the basics of Operating System, objectives, functions, types, and its role in computer systems.
Understand Batch, Multiprogramming, Multitasking, Multiprocessing, Distributed, Network, and Real-Time Operating Systems.
Learn OS services including program execution, I/O operations, file management, communication, and protection.
Study system calls, their types, implementation, and how user programs interact with the operating system.
Learn processes, process states, Process Control Block (PCB), process scheduling, and context switching.
Understand multithreading, user-level threads, kernel-level threads, and the benefits of thread-based programming.
Learn FCFS, SJF, SRTF, Priority Scheduling, Round Robin, scheduling criteria, and solved numerical examples.
Study critical section, semaphores, mutex, monitors, synchronization problems, and their solutions.
Deadlock conditions, prevention, avoidance & detection.
Paging, segmentation, swapping & allocation.
Logical vs physical memory concepts.
Internal & external fragmentation explained.
Demand paging & page replacement.
FIFO, LRU, Optimal & other page replacement techniques.
File concepts, directory structure, access methods, and file system management.
Single-level, two-level, tree-structured and graph-structured directories with examples.
Contiguous, linked, and indexed file allocation techniques explained with diagrams and examples.
Disk management techniques and scheduling algorithms like FCFS, SSTF, SCAN, C-SCAN, LOOK explained clearly.
Start with process management and CPU scheduling, since these form the base for later topics. Then move to memory management, deadlocks, and finally file systems and disk scheduling. Practicing numerical problems alongside theory helps a lot in scoring well.
These notes are designed to align with standard B.Tech CS/IT syllabuses used across most Indian universities including AKTU, RGPV, GGSIPU, and others, since the core OS concepts remain largely the same across curriculums.
Yes, every chapter includes hand-drawn diagrams for concepts like paging, segmentation, deadlock resource graphs, and disk scheduling patterns to make revision faster before exams.
Yes, Operating System is one of the most frequently asked subjects in technical interviews. Topics like process scheduling, deadlock, paging, and semaphores are commonly asked in interviews for software development, system engineering, and backend roles.
No, most Operating System concepts are explained conceptually with diagrams and numerical examples rather than actual code. A basic understanding of computer fundamentals is enough to follow along, though familiarity with C helps when studying system calls in more depth.
These notes currently cover 18 chapters, starting from the basics of what an Operating System is, moving through process management, CPU scheduling, synchronization, and deadlock, and finishing with memory management, virtual memory, file systems, and disk scheduling.