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Notes on Operating System - Chapter 1 - Operating Systems | CS 3204, Study notes of Operating Systems

Virginia Polytechnic Institute and State University (Virginia Tech)Operating Systems

Prof. C. Struble

Material Type: Notes; Professor: Struble; Class: Operating Systems; Subject: Computer Science; University: Virginia Polytechnic Institute And State University; Term: Unknown 1989;

Typology: Study notes

Pre 2010

Uploaded on 02/13/2009

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Chapter 1

Introduction

CS 3204 - Arthur 2

What is an Operating System (OS) ?

nDefinition 1:

nAn OS is the interface between the hardware and the

software environment

nDefinition 2:

nAn OS is a resource manager – provides “resource

abstraction”

nIn fact, it achieves 1 through 2.

nTherefore, both definitions are applicable at some

times.

Discover Study notes of Operating Systems Virginia Polytechnic Institute and State University (Virginia Tech)

Partial preview of the text

Download Notes on Operating System - Chapter 1 - Operating Systems | CS 3204 and more Study notes Operating Systems in PDF only on Docsity!

Chapter 1 Introduction

What is an Operating System (OS)?

n Definition 1:

n An OS is the interface between the hardware and the

software environment

n Definition 2:

n An OS is a resource manager – provides “resource

abstraction”

n In fact, it achieves 1 through 2.

n Therefore, both definitions are applicable at some

times.

CS 3204 - Arthur 3 System Software and the OS interface from the textbook

Your software

Editors

Compilers

Loaders

Drivers

Resource Abstraction n How does the OS “manage resources”?

n By providing Resource Abstraction to the other system

software and applications

n What is Abstraction?

n Abstraction hides the details

n Resource Abstraction

n hides the “nitty-gritty”details of the underlying resource

CS 3204 - Arthur 7 Resource Sharing n Managing resources through abstractions implies the ability to ‘share resources’ n Types of Sharing:

n Space Multiplexed

n Divided into 2 or more distinct units of resource

n Example: disk, memory

n Time multiplexed

n Exclusive control for a short period of time

n Example: processor

Resource Sharing n Multiple processors accessing same resource concurrently n Isolation: only one processor has access at any given time

CS 3204 - Arthur 9 Terminology n Concurrency

n The simultaneous execution of different programs

n Types of Concurrency

n Physical – multiple processors

n Example: CPU, I/O

n Logical – interleaved execution

n Example: processes

n Multiprogramming

n The concurrent execution of multiple programs on a single

processor

n Could be space-multiplexed into memory and time-

multiplexed in processors

Problems:

Simultaneous access

to memory

Lost updates

OS Strategies n Batch n Time share n PCs and Workstations n Process Control & Real-time systems n Networked

CS 3204 - Arthur 13 Time share system… from the textbook Time share… ctd. n TS eventually supported multitasking

n Multitasking:

n A time share system that support multiple processes per user,

where.

n A process is a “program in execution

n TS elevated the importance of

n Need for barriers and safeguards among users and there

processes - User/User & Process/Process

n Memory protection

n File Protection

CS 3204 - Arthur 15 Personal Computers (PCs) & Workstations n Originally

n Single User

n Single Processor

n Now

n Single or Multiple Users

n Multiprogrammed

PCs Workstations… Evolution n Earlier machines

n Too large, too expensive, and too fast for one person

n Mini-computers

n Smaller versions (like DEC PDP), yet they too grew in size

n Micro-computer

n Single chip processor

n Workstation

n Multiple user

n Multiprogrammed

n Multitasking

CS 3204 - Arthur 19 Real Time Systems… type n Hard RTS

n Had timing constraints that COULD NOT be missed

n Example: Chemical processes, Nuclear power plants,

Defense systems

n Soft RTS

n Make best effort to accommodate time constraints

n Example: Transaction processing (ATM)

RTS: Tradeoff of generality of operations/functionality to ensure that deadlines can be made Networks of Computers n Problem is too large

Notes on Operating System - Chapter 1 - Operating Systems | CS 3204, Study notes of Operating Systems

Related documents

Partial preview of the text

Download Notes on Operating System - Chapter 1 - Operating Systems | CS 3204 and more Study notes Operating Systems in PDF only on Docsity!

Chapter 1

Introduction

What is an Operating System (OS)?

n Definition 1:

n An OS is the interface between the hardware and the

software environment

n Definition 2:

n An OS is a resource manager – provides “resource

abstraction”

n In fact, it achieves 1 through 2.

n Therefore, both definitions are applicable at some

times.

Your software

Editors

Compilers

Loaders

Drivers

n By providing Resource Abstraction to the other system

software and applications

n Abstraction hides the details

n hides the “nitty-gritty”details of the underlying resource

n Space Multiplexed

n Divided into 2 or more distinct units of resource

n Example: disk, memory

n Time multiplexed

n Exclusive control for a short period of time

n Example: processor

n The simultaneous execution of different programs

n Types of Concurrency

n Physical – multiple processors

n Example: CPU, I/O

n Logical – interleaved execution

n Example: processes

n The concurrent execution of multiple programs on a single

processor

n Could be space-multiplexed into memory and time-

multiplexed in processors

Problems:

Simultaneous access

to memory

Lost updates

n Multitasking:

n A time share system that support multiple processes per user,

where.

n A process is a “program in execution

n Need for barriers and safeguards among users and there

processes - User/User & Process/Process

n Memory protection

n File Protection

n Single User

n Single Processor

n Single or Multiple Users

n Multiprogrammed

n Too large, too expensive, and too fast for one person

n Smaller versions (like DEC PDP), yet they too grew in size

n Single chip processor

n Multiple user

n Multiprogrammed

n Multitasking

n Had timing constraints that COULD NOT be missed

n Example: Chemical processes, Nuclear power plants,

Defense systems

n Make best effort to accommodate time constraints

n Example: Transaction processing (ATM)

n Partition it among machines

n Email

n File transfers

n File

n Printer

n Database

n LAN, WAN

n Client / Server