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Introduction to Computer Science

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Title: Introduction to Computer Science


1
??????? Introduction to Computer Science
??? ?????? ???? www.jiahenglu.net
2
OS Introduction, History and Concepts(?????????
??)
3
What is an Operating System?
4
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

5
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?

6
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.

7
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

8
OS
File systems
I/O devices
Monitor
Memory management
Processes, threads, scheduling
Bus
Hardware components of a computer system
Memory hierarchy
9
A Short History of Operating Systems(??????)
10
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.

11
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.
12
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

13
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
14
A Famous Remark (1943)
  • "I think there is a world market for maybe five
    computers."
  • Thomas Watson, chairman of IBM

15
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.

16
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

17
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

18
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)

19
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.

20
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

21
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

22
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)

23
Famous Forecast (1949)
  • "Computers in the future may weigh no more than
    1.5 tons."
  • Popular Mechanics, forecasting the relentless
    march of science, 1949

24
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

25
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
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