Data Representation

Data Representation

1. Binary conversions

   • Adding binary
     • 1011 +1111 11010
     • If it's a double 1 it's makes 1 and you carry another 1
     • If it's a 1 and a 0 you put a 0 and carry the 1
   • Hexadecimal and Deanery
     • 0-9 are numbers 10-15 are A-F
     • 10110111
       • First split it down the middle
         • 1011|0111
       • Then it becomes a nibble each side
       • Add up each nibble
         • 11|7
       • Then see if any are to be converted into letters
         • 11=B
       • You answer is B7
   • ASCII code
     • A=65 a=97
     • ASCII code does represent emojis Unicode does
   • Bits/nibbles
     • Bit is a single binary integer
     • 4 bits make a nibble
     • 8 bits make a bite

2. Binary images

   • Pixels
     • Pixels are the picture element so what the screen is made up of
     • You can find out how many pixels there are but finding the area of the screen
   • Black+white images/ colour images
     • If it's a black and white image 1=black and 0=white
     • For colour images black would be the highest integer and white would be the lowest
     • A bit depth is how many bits are used to represent the colours or the colour depth
     • 2 to the power of colours used x W x H = bit depth
   • Meta data
     • The resolution of the picture and colour depth
   • Lossy/lossless compression
     • Lossy compression
       • Reducing the file size
       • But you can't get it back once it's deleted
       • JPEG uses lossy compression
     • Lossless compression
       • Reducing the file size
       • You can get the data back if you want
       • PNG uses lossless compression
     • Lossless and lossy compression is when the photo becomes compressed and the quality of the photo goes down

3. Sound representation

   • The wave
     • Amplitude is how loud the sound is
     • Wavelength is the distance between a on one wave and the same point on another wave
     • It's easier to measure from the crest of one wave and the same point on the next wave
   • Frequency and pitch
     • Frequency is the pitch of a sound the closer the wave the higher the pitch. The longer the wave the lower the pitch
     • The frequency is measured in Hertz (Hz), Kilohertz (KHz) and Gigahertz (GHz)
     • A frequency of 1 Hz means one wave per cycle per second. A frequency of 10 Hz means 10 wave cycles per second where the cycles are short and closer together
   • Sound on a computer
     • Sound created on a computer exist as digital information encoded as audio files
     • Stages of making digital sound
       • 4. The computer then displays the digitalised sound for manipulation
       • 3. An analogue to digital converter digitalises the electrical voltage to bytes of information
       • 2. Microphone changes the air pressure into electrical voltage
       • 1. Microphone measures changes in air pressure