digital data encoding Flashcards
what do computers run on?
electrical energy
what do binary numbers represent?
ALL data in computers, including text, images, and sound.
what does ASCII do
has codes for every character on a standard American English keyboard
what does text file size depend on?
bits required to store each character - total number of characters in the file
what is the text file size in bits
πππ₯π‘ πΉπππ πππ§π ππ πππ‘π
= πππ‘π πππ πΆhπππππ‘ππ Γ ππ’ππππ ππ πΆhπππππ‘πππ
what are the advantages of using Unicode over ASCII
- regularly updated to support more symbols
- can represent more characters than ASCII
what are the disadvantages of using Unicode
requires more storage space, sometimes over 1 byte per character
how are images in computers represented
images in computers are represented using dots
what are the dots called
pixels
what does βpixelsβ stand for
PICture Elements
how many colours do the pixels contain
contains only ONE colour
how to form an image on a computer
- each colour is assigned a binary code
- each pixel is encoded with its colour code
- the codes for all the pixels in the image are arranged to form a bitmap
how do you determine the size of an image
the size of an image is the total number of pixels in the image
how do you calculate the size of the image
πΌππππ π ππ§π ππ πππ₯πππ = ππππ‘h Γ π»πππhπ‘.
what is colour depth
the number of colours in an image measured by the number of bits required to encode each pixel as a binary number
what is a colour scale
the RGB scale β 24 bits indicating the respective intensity of red, green and blue from 0 to 255 for each colour
what is a CLUT
colour look up table
how many bits are needed to form a colour code
2 bits
what does image file size depend on
πΆππππ’π π·πππ‘h Γ ππ’ππππ ππ πππ₯πππ
what does the quality of image depend on
- colour depth β with more colour depth,
more colours can be displayed - size β an image with more pixels is
clearer due to a higher resolution
what is sampling
the amplitude of a wave picked up at fixed times
how many bits does ASCII use per character
7 bits
how many unique values are there in ASCII
128
why does ASCII have 128 unique characters
because 7 is the base, therefore; 2^7 = 128
how does ASCII represent β48-57β in code
numbers 0 to 9 in order (eg: 48 = 0, 49 = 1, etc)
how does ASCII represent β65-90β in code
capital letters A to Z in order (eg: 65 = A, 66 = B, etc)
how does ASCII represent β97-122β in code
small letters βaβ to βzβ in order (eg: 97 = a, 98 = b, etc)
define βsample rateβ
number of samples collected in one
second
define βsample resolutionβ
number of bits used to store a single sample
how does sampling work
- a microphone picks up sound wave and converts it to an electrical analogue signal
- the signal amplitude is sampled at regular intervals
- each sample is stored as a binary value
why is sampling required
real world sound are analogue waves, which are continuous, continuous sound waves have an infinite number of amplitudes; computers do not have enough storage, so sampling is required to create digital waves (has limited number of values) which can be stored in a computer
