CSCI130

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Lecture 1 (1.1-2.3)

• CSCI130
• Instructor Dr. Imad Rahal

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General vs. Special Computers

• Labs are open book, need to bring books to lab
  every time
• Computers can either be
• Special-purpose computers (Majority)
• Hardwired to do specific tasks only (usually one)
• i.e. execute one program
• Ubiquitous --- we interact with them almost daily
  --- embedded
• Examples?
• General-purpose computers
• Provide means to change their programs thus
  becoming multi- or general-purpose machines
• Include desktops, laptops/notebooks, servers,
  etc
• People tend to associate the word computer only
  with them
• Limit ourselves to the latter type only

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Read

• 1.1-2.5
• Program Algorithms
• The History of Computing

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The History of Computing

• A computer originally meant a human being who
  did computations on paper
• Abacus was the first computing device

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The History of Computing

• Pascal (17th), Leibnitz (18th)
• Charles Babbages (19th) machine was the closest
  to todays computers
• Was programmable (not special purpose) using
  punched cards
• The punch card is a medium on which data are
  recorded by punching out holes
• Analogously, data are recorded on a DVD by
  stamping or burning much smaller holes

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An Example of a Punched Card
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The History of Digital Computing

• First generation computers
• First actual computer was developed during WWII
• Crack German code messages
• Calculate trajectories for launching shells
• Used vacuum tubes
• Can switch electricity on/off or amplify a
  current
• Much like a light bulb
• generates a lot of heat and has a tendency to
  burn out
• Slow, big (4-5 inches) and bulky

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The History of Computing

• ENIAC (shown on previous slide)
• weighed over 30 tons, and consumed 200 kilowatts
  of electrical power
• had around 18,000 vacuum tubes that constantly
  burned out, making it very unreliable
• Computers were large, programmed in machine code,
  suffered from mechanical malfunctions, expensive
  and not easy to maintain

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The History of Computing

• Second generation computers
• The transistor was invented in 1947
• Small (½ inch), fast, reliable and effective, it
  quickly replaced the vacuum tube (mid 1960s in
  computers)
• A vacuum tube had a size of 4 to 5 inches
• Machines got smaller, faster, reliable
  (transistors vs. vacuum tubes), cheaper, more
  energy-efficient with much more memory (more
  transistors could be connected in a small space)
• Development of advanced programming languages
  and applications
• No machine language anymore
• Computers became much more wide spread
• Initially restricted to governments and big
  businesses

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The History of Computing

• Third generation computers
• Late 1960s with the advent of integrated circuits
  (ICs)
• Scientists found a way to reduce the size of
  transistors so they could place hundreds of them
  on small silicon chips
• Rather than using (discrete) transistors
  separately as units, transistors were
  miniaturized and placed on silicon chips
• ICs are often classified by the number of
  transistors they hold
• More ? better
• More complicated operations

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The History of Computing

• Increased the speed and efficiency of computers
  and decreased their sizes
• Enabled whole computers to sit upon a desk top
  instead of requiring a whole room (desktops)
• More reliable, cheaper, easier to maintain with
  more memory
• Operating systems
• We are still in the 3rd generation
• IC chips are getting smaller and faster

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Analog and Digital Signals

• Signals are the basis of all communications
• Any communication that encodes a message is a
  signal
• Lights on traffic signals (G, R, Y), grade
  (performance), etc
• Phones Computers (electric signals)
• A piece of data moving from place to another that
  calls for action

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Analog and Digital Signals

• Analog signals take on a continuous set of values
• Grades
• Between any two analog signal values points, you
  can always find a 3rd value no matter what!
• Infinite possibilities
• Instruments for measurement usually give
  estimates since any value is possible
• Thermometer
• Weight scale

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Analog and Digital Signals

• Digital signals take on a discrete/finite set of
  values
• Traffic signals
• R, Y, and G
• Letter grades
• Between any two adjacent digital signal values
  points, you cant find a 3rd value
• Finite possibilities
• We can measure the exact value cannot have
  fractions
• What makes them attractive for use in computers?
• Store them in a fixed space (continuous cant)
• E.g. of students in a CSBSJU can surely be
  represented by less than 6 digits 0 - 100,000
• We have bits
• hence the name digital computers

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Overview of Computer Design

• Computers composed of 4 main components
• CPU (brain)
• Main Memory (STM)
• I/O devices (Mouth, Eyes Ears)
• Auxiliary/secondary storage (LTM)
• theoretically not needed for a functional
  computer

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Overview of Computer Design

• Data (e.g. math equation) is input through some
  input device
• Keyboard, mouse, etc
• Stored in main memory
• Think of it as our short term memory where we
  keep all things we are thinking of right now
• Stores data before and after CPU processes it
• Processed by CPU and result is stored again in
  main memory
• CPU only processes data in main memory
• Output to the user through some output device
• Screen, printer, etc
• Main memory is emptied when we turn off computer,
  if we want to save data for some period of time
• Transferred to some secondary/auxiliary storage
• Hard disk, CD, DVD, floppy disk
• Analogous to our long term memory

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Overview of Computer Design

• Memory is divided into locations/registers/words
• Each holds a fixed amount of data
• Numbers, characters
• Each has an address used to access its contents
• P.O. boxes number is address and the box is the
  register
• Each word is made of a fixed number of memory
  units called bits (Binary digITs) each having one
  of two states
• 1 means electric current is strong
• 0 no/weak electric current
• Digital or analog?
• A word is usually 8 bits (1 byte)
• Data and addresses are represented in binary
• Memory sizes are measured in bytes in groups of
• 1024 103(KB) or 1,048,576106 (MB) or 109 (GB)

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Overview of Computer Design

• The number system that we use daily is called the
  decimal system
• How many different digits?
• In computers, we have only two possibilities (0
  or 1) ? we can use the binary system
• 104103102101100 becomes 2423222120
  ...168421
• 37 3x101 7x100
• 100101 1x25 0x24 0x23 1x22 0x21 1x20

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Binary to Decimal and Vice Versa

• Binary ? decimal
• 1100 10012 ?
• 1001 10012 ?
• 0010 10012 ?
• Decimal ? Binary
• 1410 ?
• 910 ?
• 129 10 ?
• This is how we can represent (positive) numbers

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Hexadecimal

• Binary is not very convenient for humans to use
• 1001000010010010
• Instead we use the hexadecimal system (base 16)
• Group every four binary digits into a single hexa
  value
• In base 10, we have 10 digits (0-9)
• In base 2, we have 2 digits (0-1)
• What about base 16 (hexadecimal)?
• 0, 1, 2, 3.. 9, A, B, C, D, E, and F
• 163162161160 4096256161
• A1F A162 1161 F160 101616
  116 15 259110

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Binary to Hexa and Vice Versa

• From binary ? hexadecimal group 4 bits at a time
  as one hexa digit
• 10011111100100102 1001 1111 1001 0010 9F9216
• 110010012 ?
• 100110012 ?
• Group starting from left or right?
• 01010012 ?
• From hexadecimal ? binary
• 9A9216 1001 1010 1001 0010 2
• A416 ?
• 916 ?
• BC16 ?

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Unsigned Integers

• Range of values for 8-bit unsigned?
• What if we want to represent higher values? Say
  up to 300? Up to 600?
• How many bytes (or memory locations) would that
  require?