Operating system

·        An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.

·        Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.

Classification of Operating Systems

Operating systems can be classified as follows:

Multi-user: is the one that concede two or more users to use their programs at the same time. Some of O.S permits hundreds or even thousands of users simultaneously.

Single-User: just allows one user to use the programs at one time.

Multiprocessor: Supports opening the same program more than just in one CPU.

Multitasking: Allows multiple programs running at the same time.

Single-tasking: Allows different parts of a single program running at any one time.

Real time: Responds to input instantly. Operating systems such as DOS and UNIX, do not work in real time.