Introduction to Computer Science

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OS Introduction, History and Concepts(?????????
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What is an Operating System?
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Why care about OS? (1)

• Most critical software in a computer.
• OS performance influences the performance of all
  software on a computer
• How to extract the best performance out of an OS?
• How to work around design flaws? Write software
  that takes advantage of the design of the OS

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Why care about OS? (2)

• You need to understand enough to make informed
  decisions about things like
• Buying and using a personal computer
• Why do different PCs with the same CPU perform
  differently?
• Should I get Windows XP? Windows 2000? Linux?
  Whats the difference?
• Should I upgrade my hardware? Should I upgrade my
  OS?

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Why care about OS? (3)

• If youre going to be a software engineer then
  youll need to understand the environment offered
  by your OS
• What abstractions does the OS provide? E.g., the
  OS may (or may not) provide illusions such as
  infinite number of CPUs, infinite memory, single
  worldwide computing, etc.

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3 most important things youll get from this class

1. Learn how to reason about costs and tradeoffs in
   resource management at the operating systems
   level
2. Become comfortable with inter-process
   communication primitives
3. Become comfortable with system programming for
   Linux environment

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OS
File systems
I/O devices
Monitor
Memory management
Processes, threads, scheduling
Bus
Hardware components of a computer system
Memory hierarchy
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A Short History of Operating Systems(??????)
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Early Computers

• First Computer
• Charles Babbage (1791-1871) designed
• the first true digital computer called
• the Analytical Engine.
• That was purely mechanical and
• intended to do math operations
• The engine was supposed to be made of brass, and
  steam powered
• He did not actually built the machine but
  inspired others in the field.

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In 1991, on the occasion of the 200th anniversary
of the birth of Charles Babbage, the Science
Museum in Kensington, England, constructed a
complete Difference Engine from the drawings left
behind by Babbage.
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Early Computers

• Babbage also thought of the concept of software
• And hired the first programmer (Lady Ada,
  Countess of Lovelace) for his analytical engine
• From Ada Lovelaces notes The analytical machine
  was suited for "developping !!! and tabulating
  any function whatever. . . the engine is the
  material expression of any indefinite function of
  any degree of generality and complexity."
• Ada language named in her honor

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History of Operating Systems (1)

• First generation 1945 - 1955
• Technology vacuum tubes plugboards
• Programming setting some switches
• Programming language machine language
• Tasks tables of sine, cosine, logarithms
• OS none
• Computer designer is
• builder and
• programmer and
• operator and
• sys admin

Program from those days
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A Famous Remark (1943)

• "I think there is a world market for maybe five
  computers."
• Thomas Watson, chairman of IBM

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History of Operating Systems (2)

• Second generation 1955 1965
• Technology Transistors
• Programming Punched cards
• Programming languages FORTRAN Assembly
• Tasks Scientific
• Computer Mainframes
• OS Batch system
• Universities started to buy computers (millions
  )
• Separation between computer designers, builders,
  operators, programmers and maintenance personnel.

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Early Batch System

• bring cards to IBM 1401 machine (good at card
  reading)
• read cards to tape
• put tape on IBM 7094 which does computing
• put tape on IBM 1401 which prints output offline

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A Famous Remark (1957)

• "I have traveled the length and breadth of this
  country and talked with the best people, and I
  can assure you that data processing is a fad that
  won't last out the year.
• The editor in charge of business books for
  Prentice Hall

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History of Operating Systems (3)

• Third generation 1965 1980
• Technology Integrated circuits
• Programming Punched cards
• Programming languages FORTRAN Assembly
• Tasks Scientific commercial
• Computers IBM 360, DEC PDPs
• OS Multiprogramming/timesharing, spooling
• OSes Developed
• MULTICS (father of all modern OSes)
• UNIX (System V, BSD)
• POSIX (by IEEE)
• MINIX (by Tanenbaum)
• Linux (originated by Linus Torvalds, inspired by
  MINIX)

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A Famous Remark (1977)

• There is no reason anyone would want a computer
  in their home.
• Ken Olson, president, chairman and founder of
  Digital Equipment Corp.

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History of Operating Systems (4)

• Fourth generation 1980-Present
• Technology VLSI
• Programming High level
• Programming languages C/C, Java,
• Computer PC
• OS Windows, MacOS, Linux
• Cheap PCs

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A Famous Remark (1989)

• We don't see Windows as a long-term graphical
  interface for the masses.
• A Lotus Software Development official, while
  demonstrating a new DOS version

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Types of Operating Systems (1)

• Mainframe operating systems
• Room-size computers
• High I/O capacity
• Offers
• Batch processing (no interaction, such as large
  reports)
• Transaction processing (large number of small
  requests)
• Timesharing (multiple users sitting in front of
  clients)

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Famous Forecast (1949)

• "Computers in the future may weigh no more than
  1.5 tons."
• Popular Mechanics, forecasting the relentless
  march of science, 1949

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Types of Operating Systems (2)

• Server operating systems
• Offer services like print, file, or web
• UNIX, Windows 2000, Linux
• Multiprocessor operating systems
• Parallel computing
• Personal computer operating systems
• Single user with a good GUI, such as Windows 98,
  Windows 2000, Macintosh OS, Linux

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Operating Systems (3)

• Real-time operating systems
• E.g. industrial process control systems where
  each job must be completed in the specified time.
• Hard real-time (nuclear reactor control systems)
  or soft-real time systems (e.g multimedia
  systems) depending on the acceptance of missing
  deadlines
• Embedded operating systems
• Real-time systems with some resource constraints
  like memory, CPU, power.
• Smart card operating systems