Unit 2.6 - Data Representation

Unit 2.6 - Data Representation

1. Data Types

   • Bit - Binary Digit. Smallest piece of data a computer store. 1 (true) or 0 (false)
   • Nibble - 4 bits. Useful for binary > Hexadecimal
   • Byte - 8 bits. One letter is one byte
   • Kilobyte (kB) - 1,024 bytes. Document file sizes
   • Megabytes (MB) - 1,024 Kilobytes. Transmission speeds
   • Gigabytes (GB) - 1,024 Megabytes. Hard-drive sizes
   • Terabytes - 1,024 (TB) Gigabytes. V. big hard drive sizes
   • Petabytes (PB) - 1,024 Terabytes

2. Image types

   • Bitmap
     • The page is divided into an invisible grid, each pixel is assigned a colour
   • Vector
     • Drawn by following a set of mathematical instructions
     • Never blurs when zoomed in
     • Takes up less room

3. Representation methods

   • Binary
     • A number system made of 1s and 0s only
     • Only 2 possibilities, known as a base 2 number system
     • Binary is used because a CPU is made of millions of transistors that can only be in one of two states
     • Computers use it to represent data
   • Hexadecimals
     • Base 16 number system
     • 16 possibilities (0-9, A-F)
     • Convert denary into into hexadecimal by dividing by 16 and using the nth term, then add on the remainder.
     • Eg - 167/16 = 10 (A) Remainder = 7 (A7)
     • Benefits over binary
       • Binary produces long strings making it difficult to work with
       • Hex is less susceptible to error
       • Shorter = Less for programmers to remember & takes up less room
   • ASCII
     • Seven bits of data, extended ASCII uses 8 bits
     • Allows the computer to make characters
   • Unicode
     • 2 bytes - 2*16 possibilities
     • Any language covered

4. Digital Audio

   • Sample frequency - The number of audio samples captured every second
   • Sample size & Bit Depth - Number of bits available for each sample
   • Bit Rate - The number of bits used per second of audio

5. Data Compression

   • The process of encoding data so it needs fewer bits to represent it
   • Lossless
     • Compresses data files without losing information
     • Reversible, original data can be reconstructed
   • Lossy
     • Loses some of the original data
     • Can produce smaller data files
     • Deletes random characters from txt files