1.2 Text,Sound Images

How computers represent text sounds and images

Character sets

What is a character set?

  • All characters and symbols that the computer recognises/uses
  • A list of characters recognised by the computer hardware and software
  • Each character and symbol has a unique value

Unicode Vs ASCII

  • UNICODE has greater range of characters than ASCII
  • UNICODE represents most written languages in the world while ASCII does not ASCII used for English only
  • UNICODE can represent emojis, ASCII does not
  • ASCII uses 7 or 8 bits per character whereas UNICODE uses 16/32 bits per character
  • UNICODE has 60/4billion characters, ASCII has 128/256 characters

Advantage of using Unicode instead of ASCII

  • It can represent more characters
  • It can represent emojis/symbols
  • It can represent more languages

Disadvantage of using Unicode instead of ASCII

  • Each character requires more storage space

Describe how text is converted to binary to be processed by the computer?

  • A character set is used
  • ..such as ASCII/UNICODE
  • Each character has a unique binary value

Explain how the word 'RED' is represented using character set

  • Unique binary/denary number given for each character
  • The code for R is stored, then the code for E then D in sequence 

Sound

Sound Definitions

  • Sample rate: the number of samples taken per second
  • Sample resolution: is the number of bits per sample
  • pixel: One square/circle of one colour// the smallest component of the image

How does a computer represent sound?

  • A sound wave is sampled for sound to be converted to binary, which is processed by a computer

How does a computer represent sound? (NEW)

  • Recorded using a microphone
  • Sound wave is sampled…
  • …measuring the height/amplitude
  • Each amplitude has a unique binary value
  • The sample rate is set
  • …that is the number of samples taken per second
  • The sample resolution is set
  • …that is the number of bits used for each sample
  • Each sample taken is converted to binary

What happens if the sample rate/sample resolution is increased?

  • The file size will increase
  • The accuracy of the recording will increase
  • Larger dynamic range
  • Will take a longer time to download/upload

Images

Image Definitions

  • Resolution: the number of pixels in an image
  • Colour depth: is the number of bits used to represent each colour
  • Pixel: smallest component of the image

How does a computer represent images?

  • An image is a series of pixels that are converted to binary which can be processed by a computer

What happens if the colour depth/resolution is increased?

  • The file size will increase
  • The quality of the image will be increased
  • Will take a longer time to download/upload