Ch1 introduction-to-os

1.1 Silberschatz, Galvin and Gagne ©2009
Operating System Concepts – 8th Edition
Ch1: Introduction to OS
(12M)

What is an Operating System?
 A program that acts as an intermediary between a user of a computer
and the computer hardware
 Operating system goals:
 Execute user programs and make solving user problems easier
 Make the computer system convenient to use
 Use the computer hardware in an efficient manner

Four Components of a Computer System

Four Components of a Computer System
 Hardware : It is basic computing device e.g. CPU memory
 Application Program : It defines a way in which resources are used to solve
computing problem
 OS : It controls and co ordinate the use of h/w among application program
 User : who uses system

Evolution and generation
The evolutions of Operating System
 Batch Processing
 Multiprogramming
 Time Sharing
 Concurrent Programming
 Personal Computing
 Distributed Systems

Evolution and generation
There are four generation of Computer system
 1st Generation (1945-1950)
 2nd Generation (1955-1965)
 3rd Generation (1965-1980)
 4th Generation (1980-1990)

1st Generation (1945-1950)
 Mechanical part replaced by electrical
 Faster than mechanical
 Developed by Von Neumann and William Mauchely
 Make use of vacuum tube
 Due to vacuum tube occupies large space and produces heat
 Uses assembly language and no OS for this generation

2nd Generation (1955-1965)
 Vacuum tube part replaced by transistor
 Due to transistor large size and heat both problems were resolved
 Perform single job at a time
 Transistor leak some current

3rd Generation (1965-1980)
 Transistor was replaced by silicon chip
 IBM introduces range of system/360 series which is known as “family of
computer”
 DOS /360 was the OS which was used for small 360 system

4th Generation (1980-1990)
 LSI IC’s are used
 Thousands of transistor s can be mounted on single chip

Mainframe systems
 Batch
 Multi Programmed
 Multitasking
 Time sharing
 Desktop

Batch
 To speed up processing, operators batched together jobs with similar needs
and ran them through the computer as a group. Thus, the programmers
would leave their programs with the operator. The operator would sort
programs into batches with similar requirements and, as the computer
became available ,would run each batch

Multi Programmed
 Multiprogramming increases CPU utilization by organizing jobs so that the
CPU always has one to execute.
 The operating system keeps several jobs in memory simultaneously
 As long as at least one job needs to execute, the CPU is never idle
 provided an environment where the various system resources were
utilized effectively
 it did not provide user interaction with the computer system

Multitasking (time sharing)
 All the previous system utilizes resources effectively but doesn't
provide user interaction
 Time sharing (or multitasking) is a logical extension of multiprogramming
 The CPU executes multiple jobs by switching among them, but the
switches occur so frequently that the users can interact with each program
while it is running.
 the response time should be short typically within 1 second or so
 A time-shared operating system allows many users to share the
computer simultaneously

Clustered Systems
 Like multiprocessor systems, but multiple systems working together
 Usually sharing storage via a storage-area network (SAN)
 Provides a high-availability service which survives failures
 Asymmetric clustering has one machine in hot-standby mode
 Symmetric clustering has multiple nodes running applications,
monitoring each other
 Some clusters are for high-performance computing (HPC)
 Applications must be written to use parallelization

End of Chapter 1

Ch1 introduction-to-os

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