OPERATING SYSTEMS
Exam Power Notes • Quick Revision Guide
Description: Exam-focused notes covering OS fundamentals, processes, threads, CPU scheduling, memory
management, virtual memory, file systems, deadlocks, synchronization, system calls, short questions and MCQs.
Keywords: Operating Systems, OS Notes, Operating System Exam, Process Management, CPU Scheduling, Memory
Management, Virtual Memory, Deadlock, Threads, File Systems, OS MCQs, Exam Preparation, Study Notes
1. What is an Operating System?
• An Operating System (OS) is system software that manages computer hardware and provides services to application
programs.
• Main responsibilities include process management, memory management, file management, device management,
security, and resource allocation.
2. Processes & Threads
• A process is a program in execution.
• A thread is a unit of execution within a process; threads of one process can share resources.
• Common process states: New, Ready, Running, Waiting/Blocked, Terminated.
3. CPU Scheduling
• CPU scheduling selects a ready process for CPU execution.
• FCFS: First Come, First Served.
• SJF: Shortest Job First.
• Round Robin: each process receives a time slice.
• Priority Scheduling: selection based on priority.
4. Memory Management
• The OS allocates and manages memory for processes.
• Paging divides logical memory into fixed-size pages and physical memory into frames.
• Virtual memory provides a larger logical address space using secondary storage as part of the memory system.
5. File System
• A file system organizes files and directories on storage devices.
• Common operations include create, open, read, write, rename, and delete.
6. Deadlocks
• A deadlock occurs when processes wait indefinitely for resources held by one another.
• Four classic necessary conditions: Mutual Exclusion, Hold and Wait, No Preemption, Circular Wait.
• Strategies include prevention, avoidance, detection, and recovery.
7. Synchronization
• Synchronization coordinates concurrent processes or threads when they share data or resources.
• A critical section is code that accesses shared resources. Locks, mutexes, and semaphores can help control access.
8. System Calls
Exam Power Notes • Quick Revision Guide
Description: Exam-focused notes covering OS fundamentals, processes, threads, CPU scheduling, memory
management, virtual memory, file systems, deadlocks, synchronization, system calls, short questions and MCQs.
Keywords: Operating Systems, OS Notes, Operating System Exam, Process Management, CPU Scheduling, Memory
Management, Virtual Memory, Deadlock, Threads, File Systems, OS MCQs, Exam Preparation, Study Notes
1. What is an Operating System?
• An Operating System (OS) is system software that manages computer hardware and provides services to application
programs.
• Main responsibilities include process management, memory management, file management, device management,
security, and resource allocation.
2. Processes & Threads
• A process is a program in execution.
• A thread is a unit of execution within a process; threads of one process can share resources.
• Common process states: New, Ready, Running, Waiting/Blocked, Terminated.
3. CPU Scheduling
• CPU scheduling selects a ready process for CPU execution.
• FCFS: First Come, First Served.
• SJF: Shortest Job First.
• Round Robin: each process receives a time slice.
• Priority Scheduling: selection based on priority.
4. Memory Management
• The OS allocates and manages memory for processes.
• Paging divides logical memory into fixed-size pages and physical memory into frames.
• Virtual memory provides a larger logical address space using secondary storage as part of the memory system.
5. File System
• A file system organizes files and directories on storage devices.
• Common operations include create, open, read, write, rename, and delete.
6. Deadlocks
• A deadlock occurs when processes wait indefinitely for resources held by one another.
• Four classic necessary conditions: Mutual Exclusion, Hold and Wait, No Preemption, Circular Wait.
• Strategies include prevention, avoidance, detection, and recovery.
7. Synchronization
• Synchronization coordinates concurrent processes or threads when they share data or resources.
• A critical section is code that accesses shared resources. Locks, mutexes, and semaphores can help control access.
8. System Calls
