Operating system (OS)

An operating system is a program that acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs.

Some of the existing OS are:

~MS-DOS

~Windows OS

~Linus OS

~iOS mobile OS

~Android mobile OS etc

Why an os is used?

An operating system brings powerful benefits to computer software and software development. Without an operating system, every application would need to include its own User Interfaxe design, as well as the comprehensive code needed to handle all low-level functionality of the underlying computer, such as disk storage, network interfaces and so on. Considering the vast array of underlying hardware available, this would vastly bloat the size of every application and make software development impractical.

There are many different types of operating system like

**Batch OS: 

The users who using a batch operating system do not interact with the computer directly. Each user prepares its job on an off-line device like punch cards and submits it to the computer operator. To speed up the processing, jobs with similar needs are batched together and run as a group. The programmers exit their programs with the operator and the operator then sorts the programs with similar requirements into batches.

**Distributed OS:

A distributed operating system is system software over a collection of independent, networked, communicating, and physically separate computational nodes. They handle jobs which are serviced by multiple CPUs. Each individual node holds a specific software subset of the global aggregate operating system. 

**Multitasking OS:

Multitasking operating system provides the interface for executing the multiple program tasks by single user at a same time on the one computer system. For example, any editing task can be performed while other programs are executing concurrently. Other example, user can open Gmail and Power Point same time.

**Network OS:

A network operating system (NOS) is a computer operating system (OS) that is designed primarily to support workstations, personal computers and, in some instances, older terminals that are connected on a local area network (LAN). The software behind a NOS allows multiple devices within a network to communicate and share resources with each other.

**Real-OS:

real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time sharing operating system, such as Unix, which manages the sharing of system resources with a scheduler, data buffers, or fixed task prioritization in a multitasking or multiprogramming environment.

**Mobile OS:

There are numerous mobile device operating systems available today, and two of the most widely adopted are the iPhone's OS, Apple iOS, and Google's open source OS, Google Android. These two mobile OSes take different approaches to the mobile operating system.