What is operating System? Explain the abstract view of the components of a computer system.

-> An operating system (OS) is a collection of software that manages computer hardware resources and provides various services for computer programs. It acts as an intermediary between the user of a computer and the computer hardware.

-> The placement of the operating system is shown in Figure. At the bottom is the hardware, which, consists of integrated circuit chips, wires, disks, a keyboard, a monitor and similar physical devices.

-> On the top of the hardware is the software.

-> Operating system runs on the bare hardware and it provides base for the rest of the software.

-> Most computers have two modes of operation: kernel mode and user mode.

-> The operating system is the most fundamental piece of software and runs in kernel mode.

-> In this mode it has complete access to all the hardware and can execute any instruction that the machine is capable of executing.

-> The rest of the software runs in user mode, in which only a subset of the machine instructions is available. Here we find the command interpreter (shell), compilers, editors, and other system programs.

-> Finally, above the system programs are the application programs. These programs are purchased or written by the users to solve their particular problems, such as word processing,  spreadsheets, web browser or music player.

-> To hide complexity of hardware an operating system is provided. It consists of a layer of software that (partially) hides the hardware and gives the programmer a more convenient set of instructions to work with.