Text editor, Anti virus programs, Compression Tools.

It refers to the softwares which are available for use at no cost or for an optional fee.

The different types of operating system uscd in the computer:
(i) Single User and Single Task Operating Systems
(ii) Multi User Operating Systems
(iii) Multi Pocessing Operating Systems
(iv) Distributed Operating Systems
(v) Prominent Operating Systems

Ubuntu, Mint, Fedora, RedHat, Debian, Google's Android. Chrome OS, Chromium OS.

Multi-user Operating Systems:
1. It is used in computers and laptops that allow same data and applications to be accessed by multiple users at the same time.
2. The users can also communicate with each other. Windows, Linux and UNIX are examples for multi-user Operating System.

The functions of OS
(i) Process Management
(ii) Device management
(iii) Memory Management
(iv) File Management
(v) Security Management
(vi) Storage Management

(i) Single-user operating system
(ii) Multi-user Operating system
(iii) Distributed Operating system
(iv) Operating system
(v) Mobile Operating system.

(i) Easy interaction between the human and computer.
(ii) Starting computer operation automatically when power in turned on (Booting).
(iii) Controlling input & output devices.
(iv) Managing the utilization of main memory.
(v) Providing security to user program.

A mobile operating system controls a mobile device and its design supports wireless communication and different types of mobile applications. It operates 012 smart phones Tablets and Digital Mobile devices.
(i) Google Android
(ii) Apple iOS
(iii) Blackberry
(iv) Symbian

Microsoft Windows is a family of proprietary operating systems designed by Microsoft Corporation and primarily targeted to Intel architecture-based computers. Windows comes as pre-loaded on most of the new personal computers and laptops.

Microsoft Windows Home Screen
iOS - iPhone OS
iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, iPad and iPod Touch. It is the second most popular mobile operating system globally after Android.

    iPhone Home Screen

(i) File management is an important function of OS which handles the data storage techniques. The operating System manages the files, folders and directory systems on a computer.
(ii) Any type of data in a computer is stored in the form of files and directories/folders through File Allocation Table (FAT).
(iii) The FAT stores general information about files like filename, type (text or binary), size, starting address and access mode (sequential/indexed / indexed-sequential/direct/relative).
(iv) The file manager of the operating system helps to create, edit, copy, allocate memory to the files and also. updates the FAT.
(v) The OS also takes care of the files that are opened with proper access rights to read or edit them. There are few other file management techniques available like Next Generation File System (NTFS) and ext2(Linux).

The main purpose of using an operating system:
(i) It controls and coordinates all the activities of a computer system.
(ii) It provides an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner.
(iii) It enables the user to design the application, and also it provides an interface to interact with the computer and controls the execution of all kinds .of programs without knowing the internals of the hardware.
(iv) It interprets the command and instructions to perform the specified tasks.
(v) It coordinates and assigns the compilers, assemblers, utility programs to the users.
(vi) It detects errors present in the hardware and software.
(vii) It maintains the internal time clock.
(viii) It protects itself from being destroyed by any users.
(ix) It serves two major functions
1. Supervision (Prevent errors)
2. Management (Operation and control of I/O devices)
(x) It loads the programs itself into memory so that user can interact with hardware and software.

The Distributed Operating System is used to access shared data and files that reside in any machine around the world using internet / intranet. The users can access as if it is available on their own computer.
The advantages of distributed Operating System are as follows:
(i) A user at one location can make use of all the resources available at another location over the network.
(ii) Many computer resources can be added easily in the network
(iii) Improves the interaction with the customers and clients.
(iv) Reduces the load on the host computer.