2.1.4 Data Representation

Binary
1. Binary To Denary Conversion
  1. Every normal number we deal with everyday there is a binary equivalent
    1. Eg. The number 5 is 101
    2. The conversion table looks like this...
2. Binary code is made up of only 0s and 1s because its base 2
3. Computers read everything in binary. Every letter, symbol or number.
4. Binary addition is simple...
  1. You simply take your numbers and add them using these rules...
    1. 1+1=0 but you carry the one to the next column
    2. 1+0 or 0+1 = 1 with no carried numbers
    3. 0+0 = 0
Hexadecimal
1. Hexadecimal (or hex) is a number system which uses base 16
2. As we only have 10 digits, it uses 0-9 and then letters A to F
  1. Less likely to make an error with fewer characters
3. Much simpler to remember a hex value than a binary value
4. Quicker to write or type since a hex digit only takes up 1 character, not 4
  1. Easy to convert to and from binary
Images
1. The main image types are...
  1. JPEG or JPG
  2. Bitmap or BMP
  3. GIF
  4. PNG
  5. TIF
2. Pixels
  1. A pixel is the smallest identifiable area of an image
  2. Each pixel is a single colour and is given a binary value which represents that colour e.g. 11000000 might equal Red
  3. A pixel’s colour can be changed by changing this value
3. Resolution
  1. Resolution is the concentration of pixels within a specific area
  2. The area is defined by the image width and height in pixels e.g. 3264x2448
  3. 72dpi = screen resolution
  4. 300 dpi = print quality resolution
  5. The higher the resolution the better the image looks but the file size becomes a lot bigger
4. Creating Images
  1. 1. Each Pixel is given a binary value
  2. 2. Each value represents a different colour
  3. 3. Using one bit per pixel allows only 2 values, 0 and 1
  4. Eg. 1=Black White=0
Sound
1. Sampling
  1. Recording quality improves: the more frequently we sample the sound and the more accurately we record the wave height
  2. Increasing sampling rate and resolution means recording more data points
  3. Sound sampling is turning this --->
    1. To this --->
2. Lossy Compression
  1. Lossy compression removes the sounds in the frequency ranges that we can’t so easily hear or that least affect the perceived playback quality
  2. Lossy compression leaves out some data – this can affect the sound quality
3. Analogue and Digital Sounds
  1. Analogue sounds are continuous and digital sounds are discrete
  2. Sound is digitized by repeatedly measuring and recording the sound wave
4. Lossless Compression
  1. Lossless compression leaves out repeated data and instead makes a note of how many times it is repeated
5. File Formats
  1. .WAV – uncompressed files
  2. .FLAC or .M4A lossless compression, slightly smaller files
  3. .MP3 – Lossy compression, much smaller files
Machine Code
1. Machine code is the ONLY language computers can understand
  1. An instruction code is written in the form 0101 01 01001101
    1. Its made up of 0s and 1s
  2. Operands
    1. The operands are the data or memory location actually used in the operation
  3. OP Codes
    1. The 1st four binary digits are the 'op code'. Op codes are operations the computer has been coded to do automatically
    2. Eg. the code 0101 could make the computer copy a register to a memory location.
  4. Register
    1. All computers have registers. They are a volatile area to store data
    2. Computers have different amounts of registers. If the register number is two digits long, the computer has 4 registers.

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2.1.4 Data Representation

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