What is an Operating System? Introduction Guide

Operating System (OS)

An operating system is an intermediary (interface) between the user of a computer and the computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner. In other words it is also known as a system of software which may be viewed as an original collection of software consisting of processors for operating a computer and providing an environment for execution of program.

Function of an Operating System (OS)

It can act as an interface between the user and the hardware.
It is responsible for managing all the processes which are executed.
It is also responsible for managing the memory occupied by various processes.
It manages all the peripheral or I/O devices connected to the system.
It also manages the disc or the secondary storage device.
It helps in the proper functioning of the system and enables the user to interact effectively and provide instructions.

Goals of an Operating System (OS)

To execute the users program to make the process of solving the users program simple and easy.
To make the computer system convenient to use.
To use the computer hardware efficiently.

Types of Operating Systems

Type	Description	Examples
Batch OS	Jobs collected and processed in batches without user interaction	Early IBM systems
Time-Sharing OS	Multiple users share CPU time simultaneously	UNIX, Multics
Distributed OS	Multiple computers work together as one system	Amoeba, Plan 9
Real-Time OS (RTOS)	Processes data within strict time constraints	VxWorks, FreeRTOS
Network OS	Manages network resources and services	Windows Server, Novell NetWare
Mobile OS	Designed for mobile devices	Android, iOS
Embedded OS	Runs on embedded systems with limited resources	Embedded Linux, QNX

Key OS Components

Kernel: Core of the OS - manages CPU, memory, and device drivers.
Process Manager: Creates, schedules, and terminates processes.
Memory Manager: Allocates and deallocates memory to processes.
File System: Organizes and manages files on storage devices.
Device Drivers: Interface between OS and hardware devices.
Shell/CLI: Command-line interface for user interaction.

Key Takeaways

An OS acts as an intermediary between user applications and computer hardware.
The kernel is the core of the OS - it runs in privileged mode and has direct hardware access.
Process scheduling determines which process gets CPU time and for how long.
Virtual memory allows programs to use more memory than physically available by using disk space.
Modern OS use preemptive multitasking - the OS can interrupt a running process to give CPU to another.
Popular OS families: Windows (Microsoft), macOS/iOS (Apple), Linux (open-source), Android (Google).