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Summary CIE iGCSE Computer Science | Data Representation
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Contains all relevant notes for the Cambridge International GCSE Computer Science Paper 1 on compression and representing images, sound and text.
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🔉Theory 2 - Data Representation
Text
1.2.1
ASCII - Developed in 1960s as telegraph code.
Extended ASCII - Developed to include more characters.
Theory 2 - Data Representation 1
, Unicode - Uses up to 4 bytes per character — all emojis and languages can be
represented.
Sound
1.2.2
Amplitude - volume of the wave.
Frequency - pitch of the wave.
Sound sampling is used to convert the analogue wave to digital values; you can do
this by taking measurements at specific intervals. It uses an ADC (analogue to digital
converter).
An algorithm is then used to play a digital sound, however it creates a curve as it
moves from digital → analogue; there is some data loss.
To improve the representation of the sound wave:
1. Increase sample rate.
2. Increase bit depth.
How is sound stored?
MIDI allows digital music tools to produce sound: it is a series of instructions.
MP3 MIDI
Small file size. Compact and easy to modify.
Loss of quality from compression. Not as realistic.
Standard format. Same files can be played on different instruments.
Difficult to edit individual parts. Not a recording; only the notes are played.
Images
1.2.3
Resolution - total number of pixels in an image.
Pixel - smallest element in an image.
Bitmap - representing an image with an arrangement of pixels.
Theory 2 - Data Representation 2
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