Data Representations

Data Representations

1. Binary Number

   • Binary is base 2 and can be represented as a 1 or 0.
   • Conversions
     • 1 or 0 = 1 bit
     • 4 bits = 1 nybble
     • 8 bits = 1 byte
     • 1,024 bytes = 1 kilobyte
     • 1,024 kilobytes = 1 megabyte
     • 1,024 megabytes = 1 gigabyte
     • 1,024 gigabytes = 1 terabyte
   • Binary Denary conversions
     • use table: 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
       • Denary to binary
         • take the denary number and minus the largest number from the table, without making the denary number negative. at a 1 under the number from the table, and repeat until the denary number = 0
       • Binary to denary
         • in each slot that a 1 is present add the number it corasponds to the total

2. Graphics

   • Bit Map Image
     • Bit map images are made up of pixels
     • Bit map uses bits to represent colours
       • 1 bit can use 2 colours
       • 2 bits can use 4 colours
       • 4 bits can use 16 colours
       • 8 bits can use 256 colours
     • Working out how much data is needed for bit map images
       • Bits per Pixel x Resolution = bits needed to store image
     • Resolution
       • Width x Height of image
   • Vector Image
     • Vector images do not store data by pixels
     • Vector Images store data as instructions such as:
       • Colour line
       • Thickness of line
       • Fill Colour
       • Distance from origin
       • Coordinances of origin
     • Advantages:
       • Can be scaled without loss of quality
       • Use less storage space
   • Metadata
     • Term refers to "Data about data"
     • Tells about key properties needed to display the image
       • Resolution
         • Height
         • Width
       • Colour depth

3. Hexadecimal

   • Hex uses base 16 for its numbers
   • numbers up to 9 are the same in hex as in denary, however 10-15 use the alphabet A-F
   • Hex uses the table :16 | 1
     • to convert Denary to hex / by 16 for the first value, then use the remainder for the second value, then convert the numbers into hex.
     • To convert hex to denary: if any letters are present, covert them to numbers, the the first number, X by 16 then add the second number

4. ASCII

   • Stands for American Standard Code for Information Interchange
   • ASCII is used to represent all alphabetic upper and lower case characters and 32 punctuation and other symbols, which can then be stored as binary

5. Sound

   • Sound waves are analogue, making it hard for computers to store them as there is no specific measurable value so sound is stored digitally
     • The analogue wave is sampled then a digital representation of the original sound is saved.
       • The higher the sampling rate the better the quality of the sound is, however this needs more storage space.
         • The recommended sample rate is 48kHz(48,000 samples per second) because above 50kHz humans cannot tell any difference so cannot benefit from better quality.