Operating Systems Principles Lecture 1: Introduction 主講人：虞台文

Operating Systems PrinciplesLecture 1: Introduction

主講人：虞台文

Content The Role of Operating Systems

– Bridge the Hardware/Application Gap– Three Views of Operating Systems

Organization of Operating Systems– Structural Organization– The Hardware Interface– The Programming Interface– The User Interface– Runtime Organization

Operating System Evolution & Concepts


The Role of Operating Systems

PC Hardware Organization

Users ←→ Hardware

The Gap

Users ←→ Hardware

The Gap

Hardware capabilities are very low level• Arithmetic and logical operators• Comparison of two bit-strings• Branching, reading, and writing bytes

Hardware capabilities are very low level• Arithmetic and logical operators• Comparison of two bit-strings• Branching, reading, and writing bytes

User needs to think in terms of problem to be solved• High-level data structures and corresponding operations• Simple, uniform interfaces to subsystems,• Treat programs and data files as single entities

User needs to think in terms of problem to be solved• High-level data structures and corresponding operations• Simple, uniform interfaces to subsystems,• Treat programs and data files as single entities

Fills the Gap

Software

Fills the Gap

Software

Use software to bridge this gap• Language processors e.g.,

- assemblers, compilers, interpreters• Editors and text processors, linkers and loaders.• Application programs, utility and service programs.• Operating Systems

Use software to bridge this gap• Language processors e.g.,

- assemblers, compilers, interpreters• Editors and text processors, linkers and loaders.• Application programs, utility and service programs.• Operating Systems

Single CPU System

Single CPU System

I/O Devices

I/O Devices

Multiprocessor Systems

Share-Memory Model

Distributed-Memory Model

Synchronization & Communication of CPU’s

Share-Memory Model

Distributed-Memory Modelthrough the shared memory

interconnection network required.

Cash Coherence Problem

Share-Memory Model

Distributed-Memory Model

Cashes do not contain different values for the same memory element.

Cashes do not contain different values for the same memory element.

Local Cash

Multicomputer System

Multicomputer System

Network Controller

Network Controller

Local Area Networks

Local area networks (LANs) connect computers within a building or a enterprise network.

LAN network topologies:

Ring Network Broadcast Bus

Wide Area Networks

A Wide Area Network (WAN) is a collection of Local Area Networks (LANs) that have been connected together.

The internet is an example of a WAN.

Applications/ServicesApplications/Services

OperatingSystem

OperatingSystem

What are done by OS?

Process Management– Scheduling of process– Synchronization

Memory Management– Virtual memory

Input/Output Systems– Device drivers– Spooling

File Systems Protection and Security

BareMachine

BareMachine


OperatingSystem

OperatingSystem

Three Views of OS’s

BareMachine

BareMachine

User’s View

ApplicationProgrammer’

s View

SystemProgrammer’

s View


OperatingSystem

OperatingSystem

User’s View

BareMachine

BareMachine

User’s View


s View

SystemProgrammer’

s View

OS is an extended machine• Abstraction — hides complexity• Provides high level operations


OperatingSystem

OperatingSystem

Application Programmer’s View

BareMachine

BareMachine

User’s View


s View

SystemProgrammer’

s View

OS is a virtual machine• Virtualization — supports sharing• Provides virtual CPU, memory, devices


OperatingSystem

OperatingSystem

System Programmer’s View

BareMachine

BareMachine

User’s View


s View

SystemProgrammer’

s View

OS is a resource manager• Balance overall performance with individual needs e.g., response time, deadlines


Organization of Operating Systems

Structure Organization of OS

HardwareHardware

OperatingSystemKernel


SystemLibrary

Applications(system & user)

User

MachineInstructions

KernelCalls

LibraryCalls

Modes of CPU Execution

HardwareHardware



SystemLibrary


User

MachineInstructions

KernelCalls

LibraryCalls

privileged mode

nonprivileged mode

Supervisor Call (SVC)

HardwareHardware



SystemLibrary


User

MachineInstructions

KernelCalls

LibraryCalls

privileged mode

nonprivileged modeSVC

SVCs are used to implement all kernel calls and form the basic interface btw the OS kernel and the rest of the software.

The Hardware Interface

Applications and OS compiled into machine instructions

Interrupts and Traps allow OS to seize control

– process management (time-sharing)

– device management (I/O completion)

HardwareHardware



SystemLibrary


User

HardwareHardware



SystemLibrarySystemLibrary



UserUser

SVC

The Programming Interface

HardwareHardware






UserUser

MachineI nstructions

KernelCalls

LibraryCalls

Invoking system services• Library call (nonprivileged)• Kernel call (privileged)

The User Interface

HardwareHardware






UserUser

MachineI nstructions

KernelCalls

LibraryCalls

Text-based shell e.g., Unix, MS Dos– command interpreter– shell scripts

Graphics-based GUIe.g., Mac, MS Windows– windows– icons– menus– pointer

Runtime Organization

Service isa Subroutine

Service is an Autonomous Process

(client-server)


Operating System Evolution & Concepts

History of Operating Systems

The First Generation (1945–55) – Vacuum Tubes and Plugboards

The Second Generation (1955–65)– Transistors and Batch Systems

The Third Generation (1965–1980)– ICs and Multiprogramming

The Fourth Generation (1980–Present)– Personal Computers

The First Generation (1945–55) Vacuum Tubes and Plugboards



Machines of the time were so primitive that programs were often entered one bit at time on rows of mechanical switches (plugboards).

Programming languages were unknown (not even assembly languages).

Operating systems were unheard of.

The Second Generation (1955–65) Transistors and Batch Systems

A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.

Often jobs of a similar nature can be bundled together to further increase economy.



$JOB user_spec ;identify the user for accounting purposes$FORTRAN ;load the FORTRAN compilersource program cards$LOAD ;load the compiled program$RUN ;run the programdata cards$EOJ ;end of job $JOB user_spec ;identify a new user$LOAD application$RUNData$EOJ


Memory Layout of a Batch

System


The monitor is system software that is responsible for interpreting and carrying out the instructions in the batch jobs.

When the monitor started a job, it handed over control of the entire computer to the job, which then controlled the computer until it finished.

Monitor(permanently resident)

Monitor(permanently resident)

User Space

(compilers, programs,

data, etc.)

User Space

(compilers, programs,

data, etc.)

Monitor: another name of OS.


Advantages of batch systems – move much of the work of the operator to the computer – increased performance since it was possible for job to

start as soon as the previous job finished

Disadvantages – turn-around time can be large from user standpoint – more difficult to debug program – due to lack of protection scheme, one batch job can

affect pending jobs (read too many cards, etc) – a job could corrupt the monitor, thus affecting pending

jobs – a job could enter an infinite loop

The Third Generation (1965–1980) ICs and Multiprogramming

Have more than one active (running) program in memory at any one time.

Why?


Main features of this generation

CPU and I/O Overlap

Spooling

– simultaneous peripheral operations on line

Time-sharing technique


The typical CPU and I/O overlap patternin a single program


Goal of multiprogramming Keep CPUs and and I/O devices busy.


CPU Bound Programs– Perform calculation most of time– Scientific computation

I/O Bound Programs– Perform I/O most of time– Commercial data processing


TimeSaved


Spooling (simultaneous peripheral operations on line).

In spooling, a high-speed device like a disk interposed between a running program and a low-speed device involved with the program in input/output.

Example: Instead of writing directly to a printer, outputs are written to the disk. – Programs can run to completion faster; and – other programs can be initiated sooner when the

printer becomes available, the outputs may be printed.


Time Sharing Technique A variant of multiprogramming technique. Each user has an on-line terminal. Because the user is present and interacting with the

computer, the computer system must respond quickly to user requests, otherwise user productivity could suffer.

Timesharing systems were developed to multiprogram large number of simultaneous interactive users.

The Fourth Generation (1980–Present) Personal Computers

With the development of LSI circuits, chips, operating system entered entered in the personal computer and the workstation age.

Microprocessor technology evolved to the point that it become possible to build desktop computers as powerful as the mainframes of the 1970s.

The Fourth Generation (1980–Present) Personal Computers

CP/M (Control Program of Microcomputers)

MS-Dos Windows Unix

GUI

The Evolution

Early systems No Operating System

Batch Operating Systems

Multiprogramming Systems

Interactive operating Systems

Personal Computer and Workstation Operating Systems

Real-time Operating Systems

Distributed Operating Systems

Documents

Operating Systems Principles Lecture 1: Introduction 主講人：虞台文