An operating system (OS) is a software that acts as an intermediary between the computer hardware and the user applications. It manages computer resources, provides an interface for users to interact with the system, and ensures the proper execution of programs.
The main functions of an operating system include: Process management: Creating, scheduling, and terminating processes. Memory management: Allocating and managing memory resources for processes. File system management: Organizing and providing access to files and directories. Device management: Managing input/output devices and their interaction with the system.
There are several types of operating systems, including: Single-user, single-task: Supports one user and allows only one task to run at a time (e.g., early personal computers). Single-user, multi-task: Supports one user and allows multiple tasks to run concurrently (e.g., modern desktop operating systems). Multi-user: Supports multiple users simultaneously, each with their own individual sessions (e.g., server operating systems).
Process scheduling is the method by which the operating system determines the order in which processes (or threads) are executed on a CPU. It involves selecting a process from the ready queue and allocating CPU time to it. The scheduling algorithm can be based on various factors such as priority, CPU burst time, fairness, and resource availability.
Memory management involves allocating and managing the computer's primary memory (RAM) to processes and ensuring efficient utilization of memory resources. It includes tasks like memory allocation, deallocation, relocation, and swapping processes between main memory and secondary storage (like a hard disk). The operating system also handles memory protection to prevent unauthorized access or modification of memory by different processes.
There are various file systems used in operating systems, including: FAT (File Allocation Table): Used by older versions of Windows and some removable storage devices. NTFS (New Technology File System): Used by modern versions of Windows for better performance, reliability, and security. ext4 (Fourth Extended File System): Commonly used by Linux-based operating systems. HFS+ (Hierarchical File System Plus): Used by macOS.