Tuesday, June 06, 2006

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Tuesday, June 06, 2006

• I hear and I forget,
• I see and I remember,
• I do and I understand.
• -Chinese Proverb

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Today

• Course Overview
• Why a course on operating systems?
• What is an operating system?

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CS 381 Operating Systems

• Course URL
• http//suraj.lums.edu.pk/cs381m05
• Folder on indus
• \\indus\Common\cs381m05
• Website Check Regularly Course announcements,
  Slides, Resources, Policies
• Course Outline

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CS 381 Operating Systems

• Several programming exercises will be given
  throughout the course. The purpose of these
  exercises will be to give students practice in
  using the UNIX system calls, library functions,
  and algorithms.
• The development environment will be C on UNIX.

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Assumptions

• Unix shell commands
• gcc, gdb, makefile
• Text editor emacs, vi
• C programming

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Pre-requisites

• Computer Organization Assembly Language (CS
  223)
• Load registers, interrupts, DMA
• Data Structures

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What is an OS?

• Software between applications and reality
• Abstracts the underlying hardware.
• Gives illusion of changing finite into (almost)
  infinite.
• Provides protection (from malicious or buggy
  programs).

browser
spreadsheet
compiler
editor
OS
hardware
Makes reality pretty!
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Components of a simple personal computer?
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Components of a simple personal computer
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• Operating System
• Manages all the devices
• Provides users simpler interface to the
  hardware

• Efficiency.
• Convenience, ease of use.
• Optimize utilization
• E.g. mainframes expensive
• Fairness

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Intermediary between a user of a computer and the
computer hardware.
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• Extended Machine Simpler Interface
• Disk (Mechanical and Electrical components)
• Disk I/O?

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• Extended Machine Simpler Interface
• Disk I/O
• Instructions for loading device registers
• Motor On/Off, Speed, Movement of disk arm,
  sectors/tracks
• Different for different devices!

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Hide Complexity

• E.g. File interface.

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OS as Resource Manager

• Orderly and controlled access,
• Resolve conflicts
• Prevent illegal accesses
• Device I/O (Maintain queues)
• E.g. Printers
• Sharing Resources
• CPU (Time multiplexing)
• Memory (Space multiplexing)

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OS Extended example of a complex system

• Deal with complexity.
• Millions of lines of code.

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• Hardware and Operating Systems have influenced
  each other.

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• Charles Babbage (1792-1871)
• First analytical Engine
• Purely mechanical

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• Vacuum Tubes (1945-55)
• Calculating Engines
• Entire rooms
• Tens of thousands of Vacuum Tubes (problems of
  burn outs)
• Wiring up plug boards!

Seen a vacuum tube?
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• Vacuum Tubes (1945-55)
• Calculating Engines
• Entire rooms
• Tens of thousands of Vacuum Tubes (problems of
  burn outs)
• Wiring up plug boards!

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• Transistors (1955-65)
• Reliability
• FORTRAN Program punched on cards

• Problems
• CPU idle time
• I/O speeds vs CPU speeds (Mechanical vs
  Electrical)
• Costly equipment
• What if a missed?

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• Transistors (1955-65)
• Reliability
• FORTRAN Program punched on cards

• Problems
• CPU idle time
• I/O speeds vs CPU speeds (Mechanical vs
  Electrical)
• Costly equipment

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• Early batch system
• bring cards to 1401
• read cards to tape
• put tape on 7094 which does computing
• put tape on 1401 which prints output

Mostly used for scientific and engineering
calculations
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• What if a missed?
• What if it runs over the cards of another
  program?
• No protection between users

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ICs and Multiprogramming (1965-1980)

• IBM 360 series Software compatible machines
• Enormous and complex operating systems
• Costly machines
• Lead to multiprogramming
• CPU bound (scientific calculations)
• I/O bound

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ICs and Multiprogramming (1965-1980)

• Software compatible machines
• Enormous and complex operating systems
• Costly machines
• Lead to multiprogramming

Protection among users!
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• Introduction of key techniques
• Multiprogramming
• Spooling (Simultaneous Peripheral Operation On
  Line)
• From Batch systems to Timesharing

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• Introduction of key techniques (contd)
• From Batch systems to Timesharing
• I/O peoples speed
• Response time
• Memory management
• CPU scheduling
• Process Synchronization

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• MIT, Bell Labs and GE
• Machine that would support hundreds of time
  sharing users
• MULTICS (MULTIplexed Information and Computing
  Service)
• Ahead of time.

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• At Bell Labs
• One user version of MULTICS.
• Developed into UNIX

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• Linus Benedict Torvalds
• (August 1991)
• I'm doing a (free) operating system (just a
  hobby ) for 386(486) clones
• Linus himself didn't believe that his creation
  was going to be big enough to change computing
  forever.
• Linux version 0.01 was released by mid September
  1991, and was put on the net.
• Enthusiasm gathered around this project and codes
  were downloaded, tested, tweaked, and returned to
  Linus.

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• Personal Computers (1980 Present)
• Large Scale Integration (LSI)
• Intel came with 8080 which became hugely popular
• First microcontroller with disk
• DOS (Disk Operating Systems)
• Seattle Computer Products
• MS-DOS (does not support multiprogramming)
• Doug Engelbart (Mouse, GUI)
• Apple GUI
• Windows

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• Disk I/O
• Commands and accepts responses
• Instructions for loading device registers etc.
• Different for different devices!
• Device drivers (by each controller manufacturer)
• One for each OS supported.

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• Device drivers
• Run inside the kernel.
• Dynamically loaded drivers.

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• Input/Output
• Controllers have registers for communication
• Memory mapped I/O
• Separate I/O space
• Hybrid

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• Some design issues
• I/O Space
• Special IN/OUT instructions (use of assembly
  code)
• Memory mapped
• Caching of device registers should not be done!
• Multiple buses