1.User Interface: All operating systems have a user interface that allows users to communicate with the system. Three types of user interfaces are available:
a. Command line interface (CLI)
b. Batch interface
c. Graphical user interface (GUI)
2. Program execution: The operating system provides an environment where the user can conveniently run programs. It also performs other important tasks like allocation and deallocation of memory, CPU scheduling etc. It also provides service to end process execution either normally or abnormally by indicating error.
3. I/O operations: When a program is running, it may require input/output resources such as a file or devices such as printer. So the operating system provides a service to do I/O.
4.File system manipulation: Programs may need to read and write data from and to the files and directories. Operating system manages the secondary storage. Operating system makes it easier for user programs to accomplish their task such as opening a file, saving a file and deleting a file from the storage disk.
5.Communication: In the system, one process may need to exchange information with another process. Communication can be implemented via shared memory or through message passing, in which packets of information are moved between processes by the operating system.
6.Error detection: Operating systems detects CPU and memory hardware such as a memory error or power failure, a connection failure on a network or lack of paper in the printer etc.
7.Resource allocation: Operating system manages resource allocation to the processes. These resources are CPU, main memory, file storage and I/O devices.
8.Accounting: Operating system keeps track of usages of various computer resources allocated to users.
9.Protection & security: When several separate processes execute concurrently, one process should not interfere with the other processes or operating system itself. Protection provides controlled access to system resources. Security is provided by user authentication such as password for accessing information.