Operating Systems Principles Lecture 1: Introduction

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Operating Systems PrinciplesLecture 1
Introduction

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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

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Operating Systems PrinciplesLecture 1
Introduction

• The Role of Operating Systems

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PC Hardware Organization
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Users ?? Hardware
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Users ?? Hardware

• 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

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

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Fills the Gap
Software
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Fills the Gap

• 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

Software
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Single CPU System
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Single CPU System
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I/O Devices
I/O Devices
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Multiprocessor Systems
Share-Memory Model
Distributed-Memory Model
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Synchronization Communication of CPUs
Share-Memory Model
Distributed-Memory Model
through the shared memory
interconnection network required.
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Cash Coherence Problem
Cashes do not contain different values for the
same memory element.
Share-Memory Model
Distributed-Memory Model
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Multicomputer System
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Multicomputer System
Network Controller
Network Controller
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Local Area Networks

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

Ring Network
Broadcast Bus
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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.

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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

Applications/Services
Operating System
Bare Machine
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Three Views of OSs
Application Programmers View
Applications/Services
Operating System
Users View
Bare Machine
System Programmers View
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Users View

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

Application Programmers View
Applications/Services
Operating System
Users View
Bare Machine
System Programmers View
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Application Programmers View

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

Application Programmers View
Applications/Services
Operating System
Users View
Bare Machine
System Programmers View
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System Programmers View

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

Application Programmers View
Applications/Services
Operating System
Users View
Bare Machine
System Programmers View
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Operating Systems PrinciplesLecture 1
Introduction

• Organization of Operating Systems

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Structure Organization of OS
Library Calls
Kernel Calls
Operating System Kernel
Machine Instructions
Hardware
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Modes of CPU Execution
Dual-Mode Operation
Library Calls
(user mode)
nonprivileged mode
Kernel Calls
privileged mode
Operating System Kernel
(supervisor mode)
(system mode)
Machine Instructions
(monitor mode)
Hardware
(kernel mode)
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Supervisor Call (SVC)
SVCs are used to implement all kernel calls and
form the basic interface btw the OS kernel and
the rest of the software.
Library Calls
SVC
nonprivileged mode
Kernel Calls
privileged mode
Operating System Kernel
Machine Instructions
Hardware
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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)

SVC
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The Programming Interface

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

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The User Interface

• Text-based shell
• e.g., Unix, MS Dos
• command interpreter
• shell scripts
• Graphics-based GUI
• e.g., Mac, MS Windows
• windows
• icons
• menus
• pointer

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Runtime Organization
Service is an Autonomous Process (client-server)
Service is a Subroutine
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Operating Systems PrinciplesLecture 1
Introduction

• Operating System Evolution Concepts

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History of Operating Systems

• The First Generation (194555)
• Vacuum Tubes and Plugboards
• The Second Generation (195565)
• Transistors and Batch Systems
• The Third Generation (19651980)
• ICs and Multiprogramming
• The Fourth Generation (1980Present)
• Personal Computers

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The First Generation (194555) ? Vacuum Tubes and
Plugboards
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The First Generation (194555) ? Vacuum Tubes and
Plugboards
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The First Generation (194555) ? 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.

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The Second Generation (195565) ?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.

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The Second Generation (195565) ?Transistors and
Batch Systems
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The Second Generation (195565) ?Transistors and
Batch Systems
JOB user_spec identify the user for accounting
purposes FORTRAN load the FORTRAN
compiler source program cards LOAD load the
compiled program RUN run the program data
cards EOJ end of job JOB user_spec
identify a new user LOAD application RUN Data
EOJ
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The Second Generation (195565) ?Transistors and
Batch Systems
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The Second Generation (195565) ?Transistors and
Batch Systems
Monitor another name of OS.
Memory Layout of a Batch System
Monitor (permanently resident)

• 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.

User Space (compilers, programs, data, etc.)
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The Second Generation (195565) ?Transistors and
Batch Systems

• 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

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The Third Generation (19651980) ? ICs and
Multiprogramming
Have more than one active (running) program in
memory at any one time.
Why?
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The Third Generation (19651980) ? ICs and
Multiprogramming

• Main features of this generation
• CPU and I/O Overlap
• Spooling
• simultaneous peripheral operations on line
• Time-sharing technique

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The Third Generation (19651980) ? ICs and
Multiprogramming
The typical CPU and I/O overlap pattern in a
single program
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The Third Generation (19651980) ? ICs and
Multiprogramming
Goal of multiprogramming ? Keep CPUs and and I/O
devices busy.
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The Third Generation (19651980) ? ICs and
Multiprogramming

• CPU Bound Programs
• Perform calculation most of time
• Scientific computation
• I/O Bound Programs
• Perform I/O most of time
• Commercial data processing

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The Third Generation (19651980) ? ICs and
Multiprogramming
Time Saved
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The Third Generation (19651980) ? ICs and
Multiprogramming

• 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.

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The Third Generation (19651980) ? ICs and
Multiprogramming

• 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.

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The Fourth Generation (1980Present) ? 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.

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The Fourth Generation (1980Present) ? Personal
Computers

• CP/M (Control Program of Microcomputers)
• MS-Dos
• Windows
• Unix
• GUI

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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