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Four Components of a Computer System

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Four Components of a Computer System Computer System Components Users (people, machines, other computers) Applications programs define the ways in which the ... – PowerPoint PPT presentation

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Title: Four Components of a Computer System


1
Four Components of a Computer System
2
Computer System Components
  • Users (people, machines, other computers)
  • Applications programs define the ways in which
    the system resources are used to solve the
    computing problems of the users (compilers,
    database systems, video games, business programs)
  • Operating System
  • Hardware provides basic computing resources
    (CPU, memory, I/O devices)

3
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

4
What is the role of the Operating System?
  • Explore the role of the operating system from
  • The users point of view
  • The systems point of view

5
User View of a Computer
  • Varies according to the interface being used
  • Most systems designed for single user
  • OS maximizes the work (or play) user is
    performing
  • OS designed mostly for ease of use, not for
    resource utilization

6
User View of a Computer
  • Some users interface to mainframe or minicomputer
  • OS is designed to maximize resource use (CPU,
    memory, I/O)

7
User View of a Computer
  • Some users sit at workstations connected to
    networks of servers
  • Dedicated and shared resources
  • OS compromises between individual usability and
    resource utilization

8
User View of a Computer
  • What about handheld systems? (easy of use or
    resource utilization?)

9
System View of a Computer
  • OS is program most involved with the hardware
  • OS is a resource allocator
  • Manages all resources
  • Decides between conflicting requests for
    efficient and fair resource use
  • OS is a control program
  • Controls execution of programs to prevent errors
    and improper use of the computer

10
What does an Operating System do?
  • Silberschatz and Gavin An OS is similar to a
    government
  • Coordinator and Traffic Cop
  • Manages all resources
  • Settles conflicting requests for resources
  • Prevent errors and improper use of the computer
  • Facilitator
  • Provides facilities that everyone needs
  • Standard Libraries, Windowing systems
  • Make application programming easier, faster, less
    error-prone

11
What if we didnt have an Operating System?
  • Source Code?Object Code?Executable Code
  • How do you get object code onto the hardware?
  • How do you print out the answer?
  • Ealier, had to Toggle in program in binary and
    read out answer from LEDs!

12
What is an Operating System, Really?
  • Most Likely
  • Memory Management
  • I/O Management
  • CPU Scheduling
  • Communications? (Does Email belong in OS?)
  • What about?
  • File System?
  • Multimedia Support?
  • User Interface?
  • Internet Browser? ?

13
Defining Operating Systems
  • No universally accepted definition
  • Everything a vendor ships when you order an
    operating system is good approximation
  • But varies wildly
  • The one program running at all times on the
    computer is the one generally used in this
    course
  • This is the kernel
  • Everything else is either a system program (ships
    with the operating system) or an application
    program

14
Operating Systems Definition
  • No universally accepted definition
  • Everything a vendor ships when you order an
    operating system is good approximation
  • But varies wildly
  • The one program running at all times on the
    computer is the one used in this course
  • This is the kernel
  • Everything else is either a system program (ships
    with the operating system) or an application
    program

15
Computer Startup and Execution
  • bootstrap program is loaded at power-up or reboot
  • Typically stored in ROM or EEPROM, generally
    known as firmware
  • Initializes all aspects of system
  • Loads operating system kernel and starts
    execution
  • Kernel runs, waits for event to occur
  • Interrupt from either hardware or software
  • Hardware sends trigger on bus at any time
  • Software triggers interrupt by system call
  • Stops current kernel execution, transfers
    execution to fixed location
  • Interrupt service routine executes and resumes
    kernel where interrupted
  • Usually a service routine for each device /
    function
  • Interrupt vector dispatches interrupt to
    appropriate routine
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