CCST01:Computer Science and the IT Revolution

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CCST01Computer Science and the IT Revolution

• Lecturers
• Sanjay Jain (sanjay_at_comp.nus.edu.sg. S17 04--22)
• Derek Kiong (dkiong_at_comp.nus.edu.sg. S17 05--18)
• Assessment
• Final 50
• Essay assignments 30
• Tutorials 20

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CCST01Computer Science and the IT Revolution

• Introduction
• Algorithms
• Hardware
• Virtual Machine
• Networks/WWW
• Modeling, Simulation
• Abstraction, Specification, Problem Decomposition
• Artificial Intelligence
• Theory

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CCST01Computer Science and the IT Revolution

• Cryptography, Security
• Past and Future Trends
• Computers and Society
• Revision

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Introduction

• Computers are everywhere.
• They are capable of doing things for us.
• Today we will briefly see some examples of what
  they can do, and how the work they do is both
  simple and complex, similar and different

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Example Email

• Say Professor Newton at MIT wants to send email
  to me (sanjay_at_comp.nus.edu.sg).
• --- Simple Prof Newtons computer takes a string
  of characters and passes on to my computer.
• --- Complicated How does Prof Newtons computer
  know what to do with the string of letters? What
  does address sanjay_at_comp.nus.edu.sg mean? Where
  is that?

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Example Email

• Text Processing.
• detect address to send to
• which is the message part
• etc
• Server/Router
• address ending with .sg --gt send to a computer
  in Princeton, which in turn will send it to a
  computer in Singapore.
• This computer in Singapore
• comp.nus.edu.sg --gt send to a computer in
  School of Computing.

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Example Email

• This computer in School of Computing stores it
  away in a mail file.
• When I log in and execute my mail reader, it
  shows me all the messages filed in the mail file.
  
• I can then ask it to show me the mail from Prof
  Newton.

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Example Email

• To do all this work we need various machines to
  be linked together --- network using
  communication lines--- Engineering people.
• Machines need to know what to do with individual
  messages, detect the addresses, sender, message
  content etc.
• Things become complex because we need to do this
  for hundreds of millions of users, sending and
  receiving tons of mail.
• Communication lines, networks may fail, etc.

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Example Bank Account

• Depositing money is just addition, and
  withdrawing is just subtraction.
• Simple?
• Thousands of customers, at hundreds of branches.
• To do the crediting to the correct account.
• Simultaneous access.
• Information needs to travel from the ATM machine
  to the computer, and back.

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Example Bank Account

• Similar to Email in some ways. That is why we can
  use lots of similar hardware and software.
• Different We need different kind of buttons on
  the ATM machine, we need to do printing on a
  different kind of paper, need to read the ATM
  card, count money etc.
• Linc, Registration.

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• Computer, hardware may be same.
• Different interface, Different software.
• MP3 music.
• Similar to Linc database. You may search, access
  information in similar way.
• Difference is that now your machine interprets
  the information differently. It converts the
  message into sound a different interface.

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• 3D walkthrough --- video game
• --- is it similar to what we have seen so far?
• The computer has a big file describing the 3D
  structure, and can work out mathematically what
  it would look like in 2D from a particular angle.
• The software receives your position, and
  appropriately updates the 2D picture.
• Similar to how your ATM showed a different
  picture based on which account you are accessing
  or what operation you did.
• The calculations for 3D walkthrough are very
  complicated, but still similarities are there
  with other applications.

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Intelligent Computer

• Can do Email, library search, etc.
• --- store large amount of information
• --- find a particular piece of wanted
  information
• --- move the information quickly
• --- produce new information from old
  information quickly
• ---- the changes need to be specified in a step
  by step manner --- Algorithm.
• --- the variety of algorithms that we can come up
  with is where the versatility of computers come
  from.

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Intelligent Computer

• Specifying an algorithm is however not simple,
• tedious, error prone,
• Requires professional training.
• You are able to use the computer because
  professionals have already done to hard work to
  make it look simple from your end.
• Word Processing, Email, etc. require thousands or
  millions of lines of code.
• Easy to make errors.
• Y2K.

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Adding 1 to 10

• 123.10

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• sum 0
• i 1
• repeat add i to sum
• add 1 to i
• i gt 10 ?
• no -gt repeat
• yes -gt finish

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• Computer
• Memory Box Which can identify contents by name
  (address)
• Arithmetic Unit Make calculations
• Pull data from memory, send to arithmetic unit,
  put back the answers to memory, etc.
• Know when to do what.
• Sort of pressing buttons on the calculator.
• You have to specify the algorithm in the
  particular language understood by the computer.
• Programming --gt algorithmlanguage

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Intelligent Computer

• So how are we able to use computers for solving
  complicated problems?
• First trick is to generalize
• sum 0
• i n
• repeat add i to sum
• add 1 to i
• i gt m ?
• no -gt repeat
• yes -gt finish

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Intelligent Computer

• sum 0
• i n
• repeat add i to sum
• add s to i
• i gt m ?
• no -gt repeat
• yes -gt finish

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Intelligent Computer

• Second We can combine programs by using later
  programs to work on results of earlier programs.
• If we can divide in simple enough parts, then
  each part can be done separately, and then
  combined to give us the final product.

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• We do not have working algorithms for all
  problems you may want to solve.
• Even not for some simple problems.
• Face recognition.
• --- problem What exactly are we recognizing
  that is same in the photographs/persons?
• --- Some other problems are a bit more simpler.
• Finding the book by particular author in the
  huge number of books in the library is trivial
  for the computer.

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• --- Diagnosing a sickness.
• --- What questions to ask. What to do with the
  answers?
• --- Knowledge database.
• --- software here works a bit differently than
  the sum of 1 to 10.