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					Representing Information


  Semester 1, Week 2, Lect 1
Types of Information
How many groups of „types of information‟ can
  you make from the following?
     A chess board diagram.
     A satellite photograph.
     A computer program.
     Your name and address.
     The value of ∏ (PI) to 100,000 decimal places.
     A set of directions to a particular street.
     Your favourite song.
     A recording of bird-calls.

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Types of Information (2)
 Five types of information the computer
  commonly manipulates:
      Numeric (we‟ll talk about it later)
      Character
      Visual (Graphic)
      Audio
      Instructional
First, the information must be transformed (converted)
    into an acceptable representation that the
    computer will accept.
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What is Information to a Computer?
 A computer functions on electricity and
  magnetism. The magnetism is very
  often a product of electrical flow.

 There is a great deal of light and
  reflection in modern hardware (lasers
  and fibre optics) but light is a medium
  generated by electrical flow.


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What is Information to a Computer? (2)
 Electricity in a computer circuit has
  voltages (DC - direct current):
   @ +12 Volt for a disk drive,
   @ + or -5 Volt or + or -3 Volt for
     buses and communications wiring,
   @ 1.5 or 1.3 Volt for the processor.
     (Now 1.7?)



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What is Information to a Computer? (3)
 Whatever the voltage the flow can be
  switched on and off - or be present or
  absent.
   Voltage on might equal a 1,
   Voltage off might equal a 0. Binary!

 All information (instructions, data, etc.)
  flows through the hardware system as
  'Power On' or 'Power Off„ - as 1s and 0s.
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Binary Numbers
 All modern computers work with a
  system of numbers that are binary
  numbers.

 The two symbols: 0 and 1.

 Each is called a „bit‟, short for 'binary
  digit„.
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Binary Numbers (2)
 Binary circuits: Electronic devices are
  cheapest and function most reliably if
  they assume only two states.



 Open                        Closed
 circuit                     circuit




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Representation of Symbols and Text
 To store any kind of information in the
  computer‟s memory, it must first be
  transformed into a binary numeric form.
 Symbols and Text
   Includes characters, punctuation,
    symbols representing numbers.
   Each symbol can be assigned a
    numeric value.

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Representation of Symbols and Text (2)
   Two standardized sets of codes for
    symbols:
     ASCII: American Standard Code for
      Information Interchange (128
      characters. 00000002 to 11111112.
      256 characters in extended ASCII,
      000000002 to 111111112)
     EBCDIC: Extended Binary Coded
      Decimal Interchange Code.

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Representation of Symbols and Text (3)
A partial listing of the ASCII-to-binary
   character set:
Ctrl+@    0000000
Ctrl+A    0000001
Ctrl+B    0000010
Ctrl+C    0000011
Ctrl+D    0000100
Ctrl+E    0000101
Ctrl+F    0000110
Ctrl+G    0000111
Space     0100000
Delete    1111111
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0   0110000
1   0110001
2   0110010
3   0110011
4   0110100
5   0110101
6   0110110
7   0110111
8   0111000
9   0111001
:   0111010
.   1011110
         DT211-1   Computer Technology   12
A   1000001
B   1000010
C   1000011
D   1000100
E   1000101
F   1000110
G   1000111
H   1001000
I   1001001
J   1001010
K   1001011

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Representation of Symbols and Text (4)
 The message “Hello.” in Binary




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Representation of Symbols and Text (5)
 Try decoding the following:

 1010100   1001000           1001001          1010011
 0100000   1001001           1010011          0100000
 1000001   0100000           1010011          1010100
 1010101   1010000           1001001          1000100
 0100000   1010000           1010010          1001111
 1000010   1001100           1000101          1001101
 0100001




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Representation of Images
 Pictures:
   A picture must be transformed into
    numeric form before it can be stored
    or manipulated by the computer.
   Each picture is subdivided into a grid
    of squares called pixels (picture
    elements).



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Representation of Images (2)

  An image on paper can be converted
   into pixels using a scanner.
  Digital cameras store their images as
   digital images, i.e. the picture is
   already stored in the cameras
   memory as pixels.



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Representation of Images (3)




A picture with only black and white pixels:
   1 represents black.
   0 represents white.


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Representation of Images (4)
                    010101010101010101010110101101001001000111110000
                    011010101010101010101001011010010110010100000110
                    100101010101010101010110110001010000101001010100
                    101101101011011010110101100110010110100010001001
                    011010010110100101101010001001100100101101010010
                    100101101100101011010101110110011001010010101100
                    011010010011010110010010001001100110101010010001
                    010101101100101100100101110110011001010100100101
                    010101010101010011011010001001100010100001010100
                    101010101010101100010010110010001101001110100001
                    010101010101010001000101000101101000010000001101

         =          110110101010010100110100011010010011100101101000
                    101001010100100010100101100101101100001010000010
                    101011010001001001001001011110101011010100101100
                    101010000100010010010111110101111100101001001001
                    010100101001000100101010101110101011010010010000
                    101001000010011001101111101011101010101000100101
                    010010010100100011011000011110111011010110101000
                    000100000001001100100111111111110110111000000010
                    101000101010010011011000010101011101000010101000
                    000010000100101101010011111111111111011101000101
                    001000101001101010100100011101111110100010010000
                    010010010110001001001001111011110101101100100101
                    100100100000111010010010010111111111011001001000

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Representation of Images (5)
 Photographic quality images have a
  gray-scale.
  Several shades between black and
  white are used.




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Representation of Images (6)
 4 level gray-scale
   means 4 shades are
   used.
Each pixel needs 2 bits:
   00   -   represents   white
   01   -   represents   light gray
   10   -   represents   dark gray
   11   -   represents   black

This picture has 4 levels of gray
(this uses four bits).

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Representation of Images (7)
 256 level gray-scale
   means
8 bits per pixel are needed
   for 256 shades of gray.




This picture has 256 levels of gray
(this uses eight bits).

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Representation of Images (8)
 We could also use 8 bits
  (known as a byte) to
  represent the colour of a
  pixel.
 A byte can represent 256
  different numbers, so we
  can have 256 different
  colours in the image.

This picture uses 256 colours.


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Graphics Colours
 Red, Green, Blue (RGB)
   The primary light colours use three
    values per pixel.
   One number is used for each of the
    amounts of Red, Green and Blue on the
    computer screen.
                                 Red         Green       Blue




                                       Colour of pixel


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Representation of Images (again)




This is a full colour image.


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Image Resolution
 Image resolution is measured by the
  number of pixels from left to right
  across an image and the number of
  pixels from top to bottom down an
  image.
 More pixels = higher resolution = better
  quality image.



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Image Resolution (2)
 What are two specifications/attributes
  of digital cameras that indicate their
  power?
 Answer: Pixel quantity and memory
  capacity.
 E.G. Nikon Coolpix S640 (12.2 MPx, 45
  Mb) that has over twelve million pixels
  and forty-five megabytes of 'on-board'
  memory.
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Representing Sound
 Representation of any sound by using
  digital recording:
   The sound is divided into tiny
    segments and stored as binary
    numbers.
   The computer transforms these
    binary numbers and reproduces the
    voltages.


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Representing Sound (2)
    These voltages are
     sent down the
     speaker wires to
     produce sound.




                                 A sound wave represented by the sequence:

                                 0, 1.5, 2.0, 1.5, 2.0, 3.0, 4.0, 3.0, 0 (Amps)




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Representing the Instructions of
Programs
 Instructions are described as being
  imperative in the sense that they
  command action - or, at least, advise
  action.
 In most aspects of life:
   Instructions must be clearly
    understood by its intended receiver.
   The information needed to process
    the instruction must be readily
    available.
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Representing the Instructions of
Programs (2)
 Examples:
   Setting a microwave oven.
   Following a cooking recipe. (Consider
     that a recipe has a method
     (instructions) and ingredients (data)).
 It is similar with computer programs.
  Programs are all (essentially) sequential
  instructions and need to be structured
  with 'complete information'.
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Representing the Instructions of
Programs (3)
 A common book definition:
   Program: A collection or list of
     commands designed for a computer
     to follow, which gives some desired
     result.
 The structure of a program instruction
  is often logical and may include
  mathematical principles. There may
  need to be operands - also known as
  data.
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Representing the Instructions of
Programs (4)
 The difference between a recipe
  instruction and a program instruction is
  that the recipe will still work if you vary
  the method, whereas a program will
  have 'bugs' if it is not sequentially
  perfect.
 A computer‟s instructions must be
  stored in binary form within the
  computer before they can be used.

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Conclusion
 The „things‟ that a computer uses;
       Input such as data,
       That which is processed,
       Outputs
       „Feedback‟ (if used)
-   these can all be described as
    information of one sort or another.
Whatever a computer is used for, its information
  requires a method of representation for
  manipulation and storage.
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Next…

 … Number Systems -
   (Binary, Octal, Hexadecimal)




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