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Friday, August 16, 2013

PPT On Operating System Overview


Operating System Overview Presentation Transcript: 
1.Operating System Overview - 2

2.Operating System
A program that controls the execution of application programs
An interface between applications and hardware

Makes the computer more convenient to use
Allows computer system resources to be used in an efficient manner
Ability to evolve
Permit effective development, testing, and introduction of new system functions without interfering with service

4.Layers of Computer System

Portion of operating system that is in main memory
Contains most frequently used functions
Also called the nucleus

6.Evolution of an Operating System
Hardware upgrades plus new types of hardware
New services

7.Evolution of Operating Systems
Serial Processing
No operating system
Machines run from a console with display lights, toggle switches, input device, and printer
Schedule time
Setup included loading the compiler, source program, saving compiled program, and loading and linking

8.Simple Batch Systems
Software that controls the sequence of events
Batch jobs together
Program branches back to monitor when finished

9.Special type of programming language
Provides instruction to the monitor
What compiler to use
What data to use

10.Hardware Features
Memory protection
Do not allow the memory area containing the monitor to be altered
Prevents a job from monopolizing the system

11.Privileged instructions
Certain machine level instructions can only be executed by the monitor
Early computer models did not have this capability

12.Memory Protection
User program executes in user mode
Certain instructions may not be executed
Monitor executes in system mode
Kernel mode
Privileged instructions are executed
Protected areas of memory may be accessed

Processor must wait for I/O instruction to complete before preceding

When one job needs to wait for I/O, the processor can switch to the other job

15.Time Sharing
Using multiprogramming to handle multiple interactive jobs
Processor’s time is shared among multiple users
Multiple users simultaneously access the system through terminals 

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