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

(i) Software must be available free or at a low cost
(ii) Source code must be included
(iii) Anyone must be allowed to modify the source code.
(iv) Modified versions can be redistributed.

Open source based "Software refers to those categories of software/programs whose licenses do not impose much condition.

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

Multi-processing is a one of the features of Operating System. It has two or more processors for a single running process (job). Processing takes place in parallel is known as parallel processing.

(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.

(i) Distributed computing is a field of computer science that studies distributed systems.
(ii) A distributed system is a model in which components located on networked computers communicate and coordinate their actions by passing messages.
(iii) The components interact with each other in order to achieve a common goal.

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

(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).

Memory Management:
(i) Memory Management is the process of controlling and coordinating computer's main memory and assigning memory block (space) to various running programs to optimize overall computer performance.
(ii) The Memory management involves the allocation of specific memory blocks to individual programs based on user demands. At the application level, memory management ensures the availability of adequate memory for each running program at all times.
(iii) The objective of Memory Management process is to improve both the utilization of the CPU and the speed of the computer's response to its users via main memory. For these reasons, the computers must keep several programs in main memory that associates with many different Memory Management schemes.
(iv) The Operating System is responsible for the following activities in connection with memory management.
(v) Keeping track of which portion of memory are currently being used and who is using them.
(vi) Determining which processes (or parts of processes) and data to move in and out of memory.
(vii) Allocation and de-allocation of memory blocks as needed by the program in main memory. (Garbage Collection).

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.

The following algorithms are mainly used to allocate the job (process) to the processor.
(i) FIFO
(ii) SJF
(iii) Round Robin
(iv) Based on Priority
(i) FIFO (First In First Out) Scheduling :This algorithm is based on queuing technique Assume that a student is standing in a queue (Row) to get grade sheet from his/her teacher. The other student who stands first in the queue gets his/her grade sheet first and leaves from the queue (Row). Followed by the next student in the queue gets it corrected and so on. This is the basic logic of the FIFO algorithm.
(ii) SJF (Shortest Job First) Scheduling : This algorithm works based on the size of the job being executed by the CPU. Consider two jobs A and B.
1) A = 6 kilo bytes
2) B = 9 kilo bytes
First the job "A" will be assigned and then job "B" gets its turn.
(iii) Round Robin Scheduling : The Round Robin (RR) scheduling algorithm is designed especially for time sharing systems. Jobs (processes) are assigned and processor time in a circular method. For example take three jobs A, B, C. First the job A is assigned to CPU then job B and job C and then again A, B and C and so on.
(iv) Based On Priority :The given job (process) is assigned based on a Priority. The job which has higher priority is more important than other jobs. Take two jobs A and B. Let the priority of A be 5 and priority B be 7. Job B is assigned to the processor before job A.