What is an Operating System?

An operating system (OS) is system software that manages hardware resources and provides services for application software. It acts as an intermediary between the user/applications and the computer hardware. Examples include Windows, macOS, Linux, Android, and iOS.

Functions of an Operating System

1. User Interface

The OS provides a way for users to interact with the computer:

• GUI (Graphical User Interface) — windows, icons, menus, and pointer (WIMP); used in Windows and macOS
• CLI (Command Line Interface) — text-based commands typed by the user; used in Linux terminal, older systems

2. Memory Management

The OS controls how RAM is allocated to programs. It ensures programs do not access each other's memory space, and manages virtual memory when RAM is full (swapping data to secondary storage).

3. Processor (CPU) Management / Multitasking

The OS uses scheduling to share CPU time between multiple processes. It decides which process runs next and for how long, giving the impression that multiple programs run simultaneously. Common scheduling algorithms include round-robin and priority scheduling.

4. File Management

The OS organises files in a hierarchical directory (folder) structure. It controls:

• Creating, renaming, moving, and deleting files and folders
• File permissions — who can read, write, or execute a file
• File system types (e.g. FAT32, NTFS, ext4)

5. Device Management (Peripheral Management)

The OS uses device drivers — small programs that allow the OS to communicate with hardware peripherals (printers, keyboards, graphics cards, etc.). Without a driver, the OS cannot use the device.

6. Security

The OS enforces access control — requiring user authentication (login), managing user accounts and permissions, and providing firewall and encryption features.

OS Functions Summary