What is an Operating System?

An operating system (OS) is a software that takes control of your machine after it is turned on. After basic power-on self-test occurs, control is transferred to the operating system, which becomes the manager of your entire machine. Every application you run - whether Chrome, a word processor, or your own programs - must interact with the operating system to function.

The OS serves as both a manager and an interface for applications, eliminating the need for direct hardware interaction. Applications communicate with the operating system, which then handles all hardware communications on their behalf.

Why Do We Need Operating Systems?

Abstraction

Without an operating system, application development would be a nightmare. Developers would need to:

• Program the monitor to display content on screen
• Program the mouse to move the cursor
• Program the hard disk to write and save data
• Handle all hardware interactions directly in assembly or binary code

Operating systems provide system calls - standardized functions for common operations like:

• Writing data to hard disk
• Reading data from storage
• Managing mouse movements
• Displaying content on screen

These system calls work with libraries to make application development significantly easier by abstracting away hardware complexity.

Resource Management

Modern machines have limited resources but run multiple processes simultaneously. Consider a system running Chrome, Firefox, and a word processor with only a single CPU (or limited CPUs):

CPU Management: A manager must decide which process gets CPU time and when to switch between processes.

Memory Management: With limited RAM and multiple processes wanting to load, the OS determines: