Introduction to Operating System and Operating System Components

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Lecture 1

• Introduction to Operating System and Operating
  System Components

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Lecture Highlights

• What is an operating system
• Definition
• Purpose and Goals
• Operating system as part of a computer system
• Operating system components
• A closer look at some critical operating system
  functions
• Operating system classification

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Operating System Definition

• An operating system is simply a system
  application which manages user applications and
  their interaction with the system hardware.
• An operating is a program that acts as an
  intermediary between a user of a computer and the
  computer hardware.
• Operating system is a resource allocator. Much of
  the operating system theory concentrates on
  optimal use of computing resources.

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Purpose and Goals of an operating system

• The purpose of an operating system is to provide
  an environment in which a user can execute
  programs
• The two goals
• Make the computer system convenient to use
• Use the computer hardware in an efficient manner

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Goals of an operating systemConvenience vs.
Efficiency

• Convenience for user Operating systems exist
  because they are supposed to make it easier to
  compute than without one. This view is
  particularly clear when you look at operating
  systems for small personal computers.
• Efficient operation This goal is particularly
  important for large, shared multiuser systems.
  These systems are typically expensive, so it is
  desirable to make them as efficient as possible.
• These two goals, convenience and efficiency, are
  sometimes contradictory. In the past, efficiency
  considerations were often more important than
  convenience. Thus, much of the operating-system
  theory concentrates on optimal use of computing
  resources.

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Operating system as part of a computer system

• The four components of a computer system
• Hardware
• Operating system
• Application programs
• Users

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Four components of a computer system - Hardware

• It is comprised of the CPU, memory, and
  input/output devices.
• It provides the basic computing resources.

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Four components of a computer system
Application Programs

• They define the ways in which the hardware
  resources are used to solve the computing
  problems of the users.
• There are many different application programs
  e.g. compilers, database systems, games, business
  programs, etc.

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Four components of a computer system Operating
System

• The operating system controls and coordinates the
  use of the hardware among the various application
  programs for the various users.
• It provides an environment within which other
  programs can do useful work.
• It is a control program that controls the
  execution of user programs to prevent errors and
  improper use of the computer.

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Operating System Components

• Interface
• Process management
• Memory management
• I/O system management
• File Management
• Security / Protection System
• Networking
• Command-Interpreter System

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Operating System Components Interface

• The interface can be a fancy windows based or a
  command line interpreter. The issue is usually
  efficiency versus convenience. Various operating
  systems try to strike a balance between the two
  depending on specific needs.

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Operating System Components Process Management

• This component is related to the concept of
  time multiplexing for the CPU. It aims at making
  the process of switching between two programs
  transparent to the user.

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Operating System Components Memory Management

• This component is tied with the concept of space
  multiplexing.
• It entails both main memory management as well as
  secondary management.

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Operating System Components I/O System Management

• The operating system hides the peculiarities of
  specific hardware devices from the user by
  providing drivers for specific hardware devices
  on one hand and a general device-driver interface
  on the other hand.

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Operating System Components File Management

• The operating system provides a uniform logical
  view of information storage.
• It maps files onto physical media, and accesses
  these files via the storage devices.

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Operating System Components Security/Protection
Management

• In multi-user and multitasking systems, the
  various processes must be protected from one
  anothers activities. For that purpose,
  mechanisms are provided to ensure that the files,
  memory segments, CPU, and other resources can be
  operated on by only those processes that have
  gained proper authorization from the operating
  system.

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Operating System Components Networking

• Operating system usually generalizes network
  access as a form of file access, with the details
  of networking being contained in the network
  interfaces device driver.

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Operating System Components Command Interpreter
System

• Command interpreter provides the interface
  between the user and the operating system.
• The command statements deal with process creating
  and management, I/O handling, memory management,
  file-system access, protection, and networking.

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Operating System ComponentsCommand Interpreter
System (..contd)

• Operating systems are frequently differentiated
  in the area of command interpretation, with a
  user-friendly interpreter making the system more
  agreeable to some users.An example of a
  user-friendly interface is the Macintosh
  interpreter, a window and menu system that is
  almost exclusively mouse based. Depending on the
  cursor location, clicking the mouses button can
  invoke a program, select a file or directory, or
  pull down a menu containing commands.

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Operating System ComponentsCommand Interpreter
System (..contd)

• More powerful, complex, and difficult-to-learn
  interpreters are appreciated by other, more
  sophisticated users. On these interpreters,
  commands are typed on a keyboard and displayed on
  a screen or printing terminal, with the enter key
  signaling that a command is complete and is ready
  to be executed. The UNIX shells run in this mode.

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Some Critical Operating System Functions A
Closer Look

• Process Management
• Memory Management
• Input/Output Management
• General Support Functions

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Process Management A Closer Look

• Creation and Termination of processes
• Scheduling, Dispatching and Switching processes
• Synchronization, Communication and Deadlock
  Avoidance

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Process Management A Closer Look

• Creation and Termination of processes
• A process is a pre-written set of ordered
  instructions which when executed causes the
  computer to behave in a manner determined by the
  code
• A process is a program in execution
• New process are spawned either by a user or by
  other processes.

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Process Management A Closer Look

• Scheduling, Dispatching and Switching processes
• An operating system must select processes for
  execution in some fashion.
• CPU scheduling deals with the problem of deciding
  which of the processes in the ready queue is to
  be allocated the CPU.
• The selection process is carried out by an
  appropriate scheduling algorithm.

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Process Management A Closer Look

• Synchronization, Communication and Deadlock
  Avoidance
• Concurrent access to shared data can result in
  data inconsistency.
• To ensure orderly execution of processes , the
  operating system provides mechanisms for job
  synchronization and communication.
• A deadlock state is a state of indefinite wait by
  one or more processes for an event that can be
  triggered only by one of the waiting processes.
• Operating system also provides mechanisms to
  ensure that jobs do not get stuck in a deadlock,
  forever waiting for each other.

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Memory Management A Closer Look

• Memory Allocation
• Swapping
• Page and Segment Management

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Memory Management A Closer Look

• Memory management primarily deals with space
  multiplexing.
• All the processes need to be scheduled in such a
  way that all the users get the illusion that
  their processes reside on the RAM.
• The job of the memory manager
• keep track of which parts of memory are in use
  and which parts are not in use
• to allocate memory to processes when they need it
  and deallocate it when they are done
• to manage swapping between main memory and disk
  when main memory is not big enough to hold all
  the processes.

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Input/Output Management A Closer Look

• Buffer Management
• Device Allocation

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Input/Output Management A Closer Look

• One of the purposes of an operating system is
  to hide the peculiarities of specific hardware
  devices from the user. For example, in UNIX, the
  peculiarities of I/O devices are hidden from the
  bulk of the operating system itself by the I/O
  system. The I/O system consists of
• A buffer-caching system
• A general device-driver interface
• Drivers for specific hardware devices
• Only the device driver knows the peculiarities
  of the specific device to which it is assigned.

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General Support Functions A Closer Look

• Interrupt Handling
• Accounting
• Monitoring

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General Support Functions A Closer Look

• Interrupt Handling
• The occurrence of an event is usually signaled by
  an interrupt from either the hardware or the
  software.
• There are many different types of events that may
  trigger an interrupt, for example, the completion
  of I/O operation, division by zero, invalid
  memory access, and a request for some operating
  system service.
• For each such interrupt, a service routine is
  provided that is responsible for dealing with the
  interrupt.

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General Support Functions A Closer Look

• Accounting
• Accounting entails keeping track of which users
  use how much and what kinds of computing
  resources.
• This record keeping may be for billing purposes
  or simply for accumulating usage statistics.
• Usage statistics may be a valuable tool for
  researchers who wish to reconfigure the system to
  improve computing services.

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Operating System Classification

• Operating system can be classified as follows
• Multi-user
• Multiprocessing
• Multitasking
• Multithreading
• Real time

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Multi-user operating system

• A multi-user operating system allows two or more
  users to run programs at the same time. Some
  operating systems permit hundreds or even
  thousands of concurrent users.

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Multiprocessing Operating System

• A multiprocessing operating system supports
  running a program on more than one CPU.

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Multitasking Operating System

• A multitasking operating system allows more than
  one program to run concurrently.

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Multithreading Operating System

• A multithreading operating system allows
  different parts of a single program to run
  concurrently.

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Real time operating system

• A real time operating system responds to input
  instantly. General purpose operating systems,
  such as DOS and UNIX, are not real time.

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Lecture Summary

• What is an operating system
• Definition
• Purpose and Goals
• Operating system as part of a computer system
• Operating system components
• A closer look at some critical operating system
  functions
• Operating system classification

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Preview of next lecture

• The following topics shall be covered in the
  next lecture
• Process Concepts
• Performance Measures
• Evaluation Techniques