1.3 Data Storage

Question 1

how are fractions stored in binary

Answer 1

for example a quarter which is 0.25 is stored in binary as 25 with an extra byte to store the position of the decimal point “.”

Question 2

how is text stored and processed in a computer

Answer 2

every character, upper or lowercase including punctation is stored with a number code, this character code usually is ASCII but has been improved to unicode

Question 3

what does ASCII stand for

Answer 3

American Standard Code for Information Interchange

Question 4

why are there file types

Answer 4

different ways of storing digital data are called formats, different types of files use different data formats

Question 5

what is a file extension

Answer 5

3 or 4 letters after the full stop of a file name to show the data type stored in the file

Question 6

give some examples of file types

Answer 6

.txt means file holds text stored in ASCII code
.doc means file holds text + document formatting
.exe means file holds instructions which the computer can carry out, execute

Question 7

why do different file types require software to open the file

Answer 7

all files uses binary however the numbers in different file types mean different things, the computer must detect the file type so it knows what the binary represents, in some cases you need a software to open a file format

Question 8

what does a bitmap file store

Answer 8

it stores the position of every pixel and its colour that makes up an image

Question 9

why are bitmap files so large

Answer 9

because bitmap files contain the position and colour of everypixel in a number code, the full dot by dot detail

Question 10

how do vector files store data

Answer 10

by storing the mathematical formula of how to draw the lines and shapes in an image

Question 11

why are vector graphics not good for photographs

Answer 11

because they store the mathematical formula for lines and shapes, they are not good for intricatly detailed photographs, they are good for clipart or cartoons

Question 12

what is high and low resolution

Answer 12

the resolution of the image depends on how many pixels and the size of them in an image. lots of small pixels is high

Question 13

what is pixelation

Answer 13

if an image is made larger, the pixels are get larger and the resolution decrease, we say that this image is pixelated

Question 14

why are vector graphics not affected by pixelation

Answer 14

because vector graphics store the mathematical formula on how to draw the shapes and lines in an image, so they can adjust to the screen resolution when you zoom in

Question 15

what is colour depth

Answer 15

the amount of colours that can be used in an image

Question 16

give some examples of different colour formats

Answer 16

monochrome - black or white so 0 or 1
16- colour, each pixel is half a byte
156 colour, each pixel is a byte

Question 17

what are the 3 different types of sound formats

Answer 17

WAV file, MP3 and MIDI

Question 18

why is compression used

Answer 18

to reduce the size of a file for it to take less space or send quicker

Question 19

what is lossy compression

Answer 19

compression which reduces the size of the file by using algorithms that reduce the data quality such as image quality, some data is purely lost

Question 20

what is lossless compression

Answer 20

reduces the file size however no loss of data quality

Question 21

give an example of lossless compression

Answer 21

an image where a particular colour is recurring greatly, a byte will be used to store the colour and other bytes will be used to store the amount of the colour before it changes in each row, this will be less data than storing the position of each and every white pixel, this compression works good on cartoon or clipart images, images with high detail cannot work well with this

Question 22

give an example of why certain file formats have to be compressed a certain way

Answer 22

for example an .exe file where it stores instruction for the pc, cannot be compressed lossy, because we cannot afford to lose a singal command

Question 23

what are the features of lossy compression

Answer 23

some data is lost
greatly reduces the size of the file
reduces quality of sound/image
cannot be used with text or executable files

Question 24

what are the features of lossy

Answer 24

no data is lost, just encoded differently
files are recovered to their original state
can be used with all file formats
less effective at reducing file size than lossy

Question 25

what is MP3

Answer 25

MP3 is a compression technology which is usuallly used to play music on computers or mobile devices

Question 26

how does MP3 compress audio files

Answer 26

by removing sounds outside the hearing range of the human ear, or if 2 sounds are played at the same time and one is slightly quite to the ear, it will remove the quit sound so the louder sound can play
this is called perceptual music shaping

Question 27

what type of compression is MP3

Answer 27

lossy

Question 28

what type of compression is JPEG

Answer 28

lossy

Question 29

how does JPEG compress image files

Answer 29

b removing the gradations of colour or brightness which the human eye can detect, if there are multiple shades of a colour which are stored in seperate bytes, depending if the human eye can see them, or if isnt too much of a deterioration, the file can make it all one colour

Question 30

what type of compression is huffman coding

Answer 30

lossless compression on text based data

Question 31

what type of compression is run length coding

Answer 31

lossless compression on bitmap images

Question 32

what are the types of lossy compression

Answer 32

information discarding
perceptual music shaping
JPEG, MP3, MP4, WMV, MPG

Question 33

what are the types of lossless compression

Answer 33

huffman coding, runlength encoding, TIF, PDF, GIF, PNG. ZIP

Question 34

What is run length encoding

Answer 34

a lossless compression where the amount of colours and their frequencies and set in pairs, rather than storing each and every pixel position, these are called frequency/ data pairs

Question 35

director