operating systems

what is an operating system

An operating system (OS) is a program that, after being initially loaded into the computer by a boot program, manages all of the other application programs in a computer.

 
The application programs make use of the operating system by making requests for services through a defined application program interface (API).

 In addition, users can interact directly with the operating system through a user interface, such as a command-line interface (CLI) or a graphical UI (GUI).

Functions of an operating system

An operating system provides three essential capabilities: It offers a UI through a CLI or GUI; it launches and manages the application execution; and it identifies and exposes system hardware resources to those applications -- typically, through a standardized API.

Characteristics of Operating System

Memory Management: The operating system manages memory. It has complete knowledge of primary memory; which part of the memory is used by which program. Whenever a program requests, it allocates memory.
Processor Management: It allocates the program to the processor (CPU) and also deallocates it when a program runs out of the CPU needs.
Device Management: The operating system keeps the information about all devices. It is also called the I/O controller, and the operating system also decides which devices are used to which program, when, and for how long.
Security: It prevents unauthorized access to any program. It uses passwords and other technologies.
Reliability: It is very reliable because no any virus and harmful code can be detected in it.
File Management: It allocates and deallocates resources and decides which program to allocate resources.
Easy to use: It can be easily used as it also has a GUI interface.