Operating System Processes & Memory Management Revision Sheet

1. 📌 Essentials

• Processes are the fundamental units of execution, identified by PID.
• System calls like fork() create new processes; exec() replaces process image.
• Process states: ready, running, blocked; managed by the scheduler.
• Threads are lightweight subprocesses sharing the same address space.
• Virtual memory uses paging and segmentation; managed via tables.
• Page replacement algorithms include, LRU, and Clock.
• Synchronization mechanisms: semaphores, mutexes, monitors prevent race conditions.
• Hardware features: registers, interrupts, privilege modes, cache, and protection.
• Deadlock occurs with mutual exclusion, hold-and-wait, no preemption, circular wait.
• Modern OS evolution: mechanical → vacuum tube → transistor → integrated → distributed/virtualized.

2. 🧩 Key Structures & Components