Os Basics

OS Basics

What is an Operating System?

Basics of Operating Systems
bound 4, 2001

Adapted from Operating Systems Lecture Notes, Copyright 1997 Martin C. Rinard.

! Many definitions - remedy to describe what OSs do ! Provide an abstraction over computer hardware ! Standard interfaces to a variety of hardware ! Provide a user interface (not required, but most do) ! Provide an application program Programming Interface ! Manage resource sharing ! central processor, dish antenna drives, network, sound, video, keyboard, mouse, ... ! Key objectives depend on OS (e.g., Linux vs. Windows vs. PalmOS)

2

OS Basics, cont.

OS Basics, cont.

communication virtual(prenominal) railroad cars
! When hardware was expensive, objective was to keep processor fully utilized (batch processing) ! As hardware became less expensive, think shifted towards human usability ! E.g., share large servers among many simultaneous users ! straight off: At least 1 physical CPU per user ! Run many user programs on a CPU ! Complexity managed by creating an abstraction: communicating virtual machines

Communicating virtual machines, cont.
! Simple Model: Write programs as if it was the still one running on the machine ! Virtual machine implemented over a lot of interfaces that abstract a computers hardware ! Many virtual machines run concurrently on the same physical machine !



Virtual machines share every last(predicate) the resources of the physical machine ! Operating system Kernel runs and manages the virtual machines

3

4

1

OS Basics, cont.

OS Basics, cont.

Concurrency: CPU
! Process (a virtual machine): a set of instructions + a state ! The virtual machine executes from each one instruction against its state ! A state includes all the info used by the execution stream ! States implemented by a variety of hardware registers, stack, RAM, hard drive ! objective lens: Fair sharing, protection - processes cannot directly change each others states (enforced by OS) ! Communication: done through shared memory or other resources 5

Processes
! Context...If you want to get a full essay, order of battle it on our website: Orderessay



If you want to get a full essay, wisit our page: write my essay .