Data Flashcards
(33 cards)
what is a character set?
a character set is a table that matches together a character and a binary value
what are the two common character sets?
ASCII and unicode
why are character sets necessary?
they allow computers to exchange data
Describe 3 differences between ASCII and unicode?
ASCII
- uses binary
- tiny set of characters
- less memory required per character
Unicode
- uses hexadecimal
- large set of characters
- more memory required per character
what does ASCII stand for?
American standard code for information interchange
how many different data types are there?
5
what is a character ?
give an example
a single character , such as a letter, number, punctuation or symbol
e.g. T 8 ?
what is a string?
give an example
a sequence of characters, including letters, numbers and punctuation
e.g. harry styles
14:50 pm
cinderella 2
what is an integer?
give an example
a whole number
e.g. 475
-84
10
what is a real?
give an example
a decimal number
- 5.21
0. 01345
what is a boolean?
give an example
an answer that only has two possible values
true/false
yes/no
0/1
what data type are telephone numbers stored as ?
string
what are the two main type of graphics used in a computer system?
raster (aka bitmap)
vector
describe 3 differences between raster(bitmap) and vector images
give examples
Raster
- made up of a grid of pixels
- if scaled to a larger size, image loses image quality
- generally larger in size as data is stored for each pixel
e. g. photographs and screenshots
Vector
- use objects (lines and shapes) to mathematically form shapes
- if scaled to a larger size, does not lose any image quality
- generally smaller in file size
e. g. logos and cartoons
formula to calculate file size
file size = resolution x colour depth
what is the colour depth/bit depth?
the number of bits that are used to represent each pixel’s colour
how many colours can be represented with a colour depth of 1 bit 2 bit 3 bit 5 bit 1 byte ?
1 = 2 colours 2 = 4 colours 3 = 8 colours 5 = 32 colours 1 byte (8 bits) = 256 colours
what is the RGB colour model?
the red green blue colour model uses 3 bytes (a byte of 256 red green and blue shades ) that together can represent 16.7 million different colours
what is metadata?
give examples of image metadata
metadata is additional information about a file
e.g dimensions colour depth make model orientation exposure time
what is metadata?
give examples of image metadata
metadata is additional information about a file
e.g dimensions colour depth make model orientation exposure time
an image file has a width of 120 pixels , a height of 120 pixels and a colour depth of 1 . what is the file size in bytes
resolution is height x width
120 x 120 = 14400
colour depth = 1 bit
file size = resolution x colour depth
file size = 14400 x 1 = 14400
file size in bytes = 14400 / 8 = 1800 bytes
how is an analogue sound wave converted to digital data (binary) ?
the sound is sampled using an ADC (analogue to digital convertor) and stored as a binary value called a sample
what is a sample rate?
what is it measured in?
- the number of samples taken per second
- measured in kilohertz (kHz)
explain 2 ways an audio file will be affected if the sample rate is increased
- the higher the sample rate the better the audio quality as the digital data more closely resembles an analogue wave
- higher sample rates result in larger file sizes because more data is stored for each individual sample
