what is an Operation system and operating system as an extented machine.

OPERATING SYSTEM-DEFINITION

·        An operating system is a program that acts as an interface between the user of a computer and the computer hardware. The purpose of operating system is provide an environment in which a user can execute programs in a convenient and efficient manner.

·        An eperating system is a fist program that gets loaded into the memory through a pročess called booting.

·        We can say that an operating system is an integrated set of programs that manages the various hardware resources such as processors, memory, I/o devices, communication devices and the overall operations of a computer system.

·        Its primary objective is to improve the performance and efficiency of a computer system and make it user friendly. Thus, like a manager of a company, an operating system is responsible for smooth and efficient operation of the entire computer system .

·        An operating system also acts as a platform on which various application programs such as word processor and excel are executed.

·        The most common operating system are the windows family of operating system (Windows 98, Windows 2000, NT, Vista and Windows 7), UNIX and Macintosh operating system.

Operating System as an Extended Machine

·        An operating system is a layer of software on the top of the bare hardware of a computer system.

·        This operating system manages all parts of the system, and presents to the user with an interface or virtual machine, that is easier to program and use.

·        It means, that the operating system hides the details of the hardware resources from the programmer and provides the programmer with a convenient interface for using the computer system. This is called abstraction.

·        Thus, the abstraction feature of operating system hides the lower level details from users and provides a set of higher level function to users.

·        The operating system acts as an intermediary between the hardware and its users, providing a high level interface to low level resources, and making it easier for the programmer and other users to access and use those resources.

·        Figure shows the logical architecture of computer system. The hardware resources are surrounded by the operating system layer which in turn is surrounded by a layer of other system softwares such as compilers, editors, assemblers, loaders etc. and by a set of application programs such data processing applications, scientific and engineering application, entertainment and education applications etc.

Finally, the end users view the computer system in terms of the user interfaces provided by the application programs.

·        Thus the purpose of the operating system is to present the user wi equivalent of an extended machine or virtual machine that is easier to program than the underlying hardware.