Data Representation

Data Representation

1. Images

   • Bitmaps
     • Image divided into a grid of pixels
       • Each pixel set to a number of bits, which can contain a set number of colours
         • If the pixel contains 4 bits, it can contain up to 2^^4 number of colours (16)
           • Increasing the size of the image increases the size of the file as there are more pixels
             • Increasing the resolution (quality) also increases file size
     • The width of the picture is needed in pixels as well as the number of bits assigned to each pixel
   • Vector Images
     • These images do not have any data pixels but they are a specific set of instructions needed to reproduce the picture
       • Certain elements of the picture are required to make the instructions
         • Shape
         • Line thickness
         • FIll
         • Colour Depth
     • Vector images build their instructions in relation to the photo's point of origin
       • As the picture is only a set of instructions, resizing the photo does not affect the resolution of the picture
         • Therefore file size is small

2. Metadata

   • Known as "data about data"
     • vector images need metadata

3. Number systems

   • Binary
     • Base 2 counting system, where only the numbers 0 or 1 are used
       • Computers read data in binary
   • Denary
     • Base 10 counting system where the numbers 0 to 9 are used
       • Humans use denary to count
   • Hexadecimal
     • Base 16 counting system where the numbers 0 to 9 are used, and the letters A, B, C, D, E, F are used to represent the numbers 10, 11, 12 ,13 ,14 15 respectively

4. Units of Information

   • Bit
     • Nybble
       • Byte
         • Kilobyte
           • Megabyte
             • Gigabyte
               • Terabyte
                 • Petabyte
                   • Exabyte
                     • Yottabyte
                       • Zettabyte

5. Sound

   • Sound waves are analogue, so they must be converted to digital information for computers
     • This is done by sampling the wave and storing a digital representation of the sound
       • Sampling frequency is how often a sound wave is sampled
         • Increasing sample frequency produces a better quality of sound but increases file size
       • Sample rate determines how many different tones can be represented
         • High sample rate means more tones can be represented