Give and explain the view of OS as an extended machine

-> Operating systems perform two basically unrelated functions: providing a clean abstract set of resources instead of the messy hardware to application programmers and managing these hardware resources.
-> The architecture (instruction set, memory, I/O, and bus structure) of most computers at the machine level language is primitive and awkward to program, especially for input/output operations.
-> Users do not want to be involved in programming of storage devices.

-> Operating System provides a simple, high level abstraction such that these devices contain a collection of named files.

-> Such files consist of useful piece of information like a digital photo, e mail messages, or web page.

Operating System provides a set of basic commands or instructions to perform various operations such as read, write, modify, save or close. 

-> Dealing with them is easier than directly dealing with hardware.

-> Thus, Operating System hides the complexity of hardware and presents a beautiful interface to the users.

-> Just as the operating system shields (protect from an unpleasant experience) the programmer from the disk hardware and presents a simple file-oriented interface, it also conceals a lot of unpleasant business concerning interrupts, timers, memory management, and other low level features.

-> In each case, the abstraction offered by the operating system is simpler and easier to use than that offered by the underlying hardware.

-> In this view, the function of the operating system is to present the user with the equivalent of an extended machine or virtual machine that is easier to work with than the underlying hardware.

-> The operating system provides a variety of services that programs can obtain using special instructions called system calls.