The different types of operating system used in the computer
(i) Single User and Single Task Operating System
(ii) Multi User Operating System
(iii) Multi Processing Operating System
(iv) Distributed Operating System
(v) Prominent Operating System

This is a one of the features of Operating System. It has two or more processors for a single running process (job).

The Operating System provides three levels of securities to the user end. They are
(i) File access level
(ii) System level
(iii) Network level.

(i) Controlling input and output devices.
(ii) Managing computer resources such as Central Processing Unit, memory, Disk drives and printers.
(iii) Executing and providing services for application software.
(iv) Establishing a user interface.

The GUI is a window based system with a pointing device to direct I/O, choose from menus, make selections and a keyboard to enter text. Its vibrant colours attract the user very easily.

(i) Keeping track of which portion of memory are currently being used and who is using them.
(ii) Determining which processes (or parts of processes) and data to move in and out of memory.
(iii) Allocation and de-allocation of memory blocks as needed by the program in main memory. (Garbage Collection).

(a) Multi-user OS
(b) Distributed OS
(c) Single user OS

(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.

(i) Multiprocessing is the use of two or more CPUs within a single computer system.
(ii) A system is said to be multiprocessing if it has more than one physical processors. Since it has multiple processors available, multiple processes can be executed at a time.
(iii) In Multiprocessing, processes can be assigned to a different processor for its execution.
(iv) With the help of multiprocessing system more work can be done in a shorter period of time.
(v) Multiprocessing system provides increased reliability means that if one processor fails, the other processor will continue its working. For example, if there are10 processors and 1 fails then the work does not halt, instead the remaining 9 processor will share the work of 10 th processor.
(vi) Multiprocessing system increases the Throughput i.e. if we increase the number of processors, more work can be completed.
(vii) As multiprocessing occurs by parallel processing, it is cost saving since it parallelly shares memory, buses, peripherals, etc.
(viii) Multiprocessor refers to hardware (CPU units) rather than software (running programs).

User interface:
(i) It is one of the important features of an Operating system.
(ii) User interface allows user to interact with computer effectively.
(iii) An interactive Operating system provides astonishing feature of Graphical User Interface.
(iv) GUI is one of the advanced features that have made Windows and other interactive Operating system highly popular.
(v) Some properties of GUI are display of icons, movement of cursor, etc.
Memory Management:
(i) Operating system performs the function of memory management. Memory Management is the process of controlling and coordinating with computers main memory.
(ii) The Operating system keeps a track of main memory/primary memory i.e. which portion of memory is currently being used and who is using them.
(iii) Memory Management involves allocation and de-allocation of memory blocks.
File Management:
(i) File Management is an important function of Operating System that maintains and manages file operation.
(ii) File Management manages files, folder and directory system on computer.
(iii) The process of File Management includes creating, modifying and deleting of files.
(iv) File Management of Operating system helps to create new files and place them at specific location and makes the process of sharing of files easy.
Process Management:
(i) Process Management includes creation and deletion of processes.
(ii) Process Management provides mechanism for communication and synchronization of processes.
I/O Management:
(i) The Operating system is responsible for all sorts of input from keyboard, mouse, desktop, etc.
(ii) Operating system effectively handle I/O operation to hide the peculiar behavior from the end-user.
Security Management:
(i) Operating system provides security by protecting unauthorize access to computer and uses password and other similar technique to protect user data

Time-Sharing Operating Systems
Advantages	Disadvantages
Provides the advantage of quick response.	Problem of reliability.
Avoids duplication of software.	Questions of security and integrity of uses programs and data
Reduces CPU idle time.	Problem of data communication.

(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).