1.2 text, sound and images
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unicode vs ASCII
• unicode allow greater range of characters and symbols • unicode require more bits per character
how does a computer represent text a text in binary
use character set - collection of characters - and corresponding binary codes that represent them
describe data storage in ASCII
• 7bit • use 1 byte to store value (MSB is 0)
how does computer represent sound digitally
• sound wave sampled (convert from analogue to digital) • sampled at regular time intervals where amplitude is measured • cannot be measured precisely, so approx values stored
how is sound recorded
• amplitude of sound wave first determined at set time intervals • value converted to digital form • each sample of sound wave encoded as series of binary digits • series of readings gives approx representation of wave
what is sample resolution
number of bits per sample
effect of increasing sampling resolution
• increases accuracy of sampled sound (more detail stored about amplitude) • increases memory usage of file (more bits used to store data)
what is sampling rate
• number of sound samples taken per second • measured in hertz (Hz)
effect of increasing sample rate
• more accurate sound • fewer estimations done between samples
what is an image
• series of pixels that are converted to binary • which is processed by a computer
define character set
• all characters and symbols • that can be represented by a computer system • each chara/symbol assigned unique value
what is colour depth
• number of bits representing each colour
effect of increasing colour depth
• increases accuracy of colours • increases file size
what is image resolution
number of pixels that make up an image
effect of increasing image resolution
• more detailed images • increased memory use