Structure of Operating System

Introduction

• The Operating System (OS) works as an interface between computer hardware and applications.
• Main Objectives: Memory management, process scheduling, disk management, and process management.

Types of Operating Systems

• Android: For mobile devices
• iOS: For Apple's devices
• Windows: For personal computers
• Linux/Unix: For servers and other uses
• RTOS (Real-Time OS): For military applications and IoT devices

Multiprogramming, Multiprocessing, Multitasking, and Multithreading

• Multiprogramming: Presence of multiple programs in the memory at one time
• Multiprocessing: Running multiple processes simultaneously in a system
• Multitasking: Dividing CPU time
• Multithreading: Inclusion of multiple threads in a process

Process States

• New: Process is being created
• Ready: Process is ready for execution
• Running: CPU is executing the process
• Waiting: Waiting for input/output operation
• Terminated: Process has completed

CPU Scheduling Algorithms

• FCFS (First-Come, First-Served): First process comes first
• SJFS (Shortest Job First): Shortest process comes first
• Round Robin: Equal time quantum
• Priority Scheduling: Process with highest priority comes first

Process Synchronization

• Mutual Exclusion: Only one process accesses the critical section at a time
• Progress: At least one process should progress
• Bounded Waiting: Limited waiting time
• Locks/Mutex: Locks for one process
• Semaphore: Locking with count limit
• Read-Lock/Write-Lock: Locking for reading and writing

Deadlock

• Conditions: Mutual exclusion, hold and wait, no preemption, circular wait
• Handling Techniques: Prevention, avoidance, detection, recovery, ignorance

Memory Management

• Fixed Partitioning: Fixed-size partitions
• Dynamic Partitioning: Dynamic size partitions
• Paging: Small, fixed-size pages
• Virtual Memory: Optimal memory utilization
• Page Replacement Algorithms: FIFO, LRU, avoiding thrashing

Secondary Storage

• Disk Structure: Tracks and sectors
• Disk Scheduling Algorithms: FCFS, SSTF, SCAN, LOOK

Conclusion

• The purpose of all the above points is to ensure that you have complete knowledge about the operating system. This lecture is important for both interviews and exams.