UNIX

(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.

Different operating system used:
1. Single user, single Task Operating system
2. Multi user operating system
3. Multiprocessing operating system
4. Distributed Operating system

Multiprocessing is one of the features of operating system. It has two or more processors for a single running process. Each processor works on different parts of the same task or two or more different tasks.

Security Management features:
File access level security, System level security, Network level security.

Operating systems for mobile devices
Mobile devices such as phones, tablets and MP3 players are different from desktop and laptop computers and hence they need special Operating Systems. Examples of mobile Operating Systems are Apple iOS and Google Android. The iOS running on an iPad is

Operating systems for mobile devices generally are not as fully featured as those made for desktop and laptop computers and they are not able to run all software.

(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.

(i) This algorithm is based on queuing technique. This is the basic logic of the FIFO algorithm.
(ii) Technically, the process that enters the queue first is executed first by the CPU, followed by the next and so on.
(iii) The processes are executed in the order of the queue (row).

(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 benefits of open source are tremendous and have gained huge popularity in the IT field in recent years. They are as follows:
1. Open source (OS) is free to use, distribute and modify.
2. Open source is independent of the company as author who originally created it.
3. It is accessible to everyone. Anyone can debug the coding.
4. It doesn't have the problem of incompatible formats that exists in proprietary software.
5. It is easy to customize as per our needs.
6. Excellent support will be provided by programmers who will assist in making solutions. Some of the disadvantages are:
7. Latest hardware are incompatible, i.e. lack of device drivers.
8. It is less user friendly and not as easy to use.
9. There may be some indirect costs involved such as paying for external support.
10. Malicious users can potentially view it and exploit any vulnerability.