MS-DOS, Windows, Linux, ios are common OS in the world.

1. MS-DOS:
MS-DOS which is short for Microsoft Disk Operating System is a non-graphical command line operating system developed for IBM compatible computers with x86 microprocessor. The operating system used a command line interface for the user to input commands to navigate, open and manipulate files on their computer.

Features:

1. It is a single user operating system meaning only one user can operate at a time.


2. It is a light weight operating system allowing users to have direct access to the BIOS and its underlying hardware.


3. Loads data and programs from external sources and bring them into the internal memory so they can be used on the computer.


4. Enables the computer to perform input and output operations such as taking commands from keyboard, printing information on the screen.


5. It is very helpful in making file management like creating, editing, deleting files, etc.


6. It also controls and manages other external devices such as the printer, keyboard or external hard drive using various drive utilities.

2. Windows Operating System:
Windows is an operating system designed by Microsoft to be used on a standard x86 Intel and AMD processors. It provides an interface, known as a graphical user interface(GUI) which eliminates the need to memorize commands for the command line by using a mouse to navigate through menus, dialog boxes, buttons, tabs, and icons. The operating system was named windows since the programs are displayed in the shape of a square. This Windows operating system has been designed for both a novice user just using at home as well as for professionals who are into development.

Features:

1. It is designed to run on any standard x86 Intel and AMD hence most of the hardware vendors make drivers for windows like Dell, HP, etc.


2. It supports enhanced performance by utilizing multi-core processors.


3. It comes preloaded with many productivity tools which helps to complete all types of everyday tasks on your computer.


4. Windows has a very large user base so there is a much larger selection of available software programs, utilities.


5. Windows is backward compatible meaning old programs can run on newer versions.


6. Hardware is automatically detected eliminating need of manually installing any device drivers.

3. LINUX Operating System:
The Linux OS is an open source operating system project that is a freely distributed, cross-platform operating system developed based on UNIX. This operating system is developed by Linus Torvalds. The name Linux comes from the Linux kernel. It is basically the system software on a computer that allows apps and users to perform some specific task on the computer. The development of Linux operating system pioneered the open source development and became the symbol of software collaboration.

Features:

1. Linux is free can be downloaded from the Internet or redistribute it under GNU licenses and has the best community support.


2. Linux OS is easily portable which means it can be installed on various types of devices like mobile, tablet computers.


3. It is a multi-user, multitasking operating system.


4. BASH is the Linux interpreter program which can be used to execute commands.


5. Linux provides multiple levels of file structures i.e. hierarchical structure in which all the files required by the system and those that are created by the user are arranged.


6. Linux provides user security using authentication features and also threat detection and solution is very fast because Linux is mainly community driven.

7. iOS  Operating System:
iOS which is short for iPhone OS is a mobile operating system created and developed by Apple Inc. exclusively for its hardware like A12 Bionic chip that presently powers many of its mobile devices, including the iPhone, iPad, and iPod. The iOS user interface is based upon using multi-touch gestures such as swipe, tap, pinch, and reverse pinch. The purpose of these finger actions is to provide the user with fast responsive inputs given from multiple fingers to the multi-touch capacitive screen display.

Features:

1. It is written in C, C++, Objective-C and Swift and is based on the Macintosh OS X.


2. Has excellent and intuitive user interface and very fluid response.


3. Performance of iOS is unbeatable.


4. iOS comes with a lot of default apps, including an email client, web browser, media player and the phone app.


5. Availability of higher quality apps which can be downloaded from the Appstore.


6. Apple has provided its own iOS software development kit (SDK) for the developers to create applications for Apple mobile devices.


7. iOS is much safer than other mobile operating systems and has fewer security breaches as well.


8. Provides regular updates and security patches.