Data Representation (paper 1) Flashcards
what is the order for the memory size
bit
nibble
byte
kibibyte
mebibyte
gibibyte
tebibyte
pebibyte
Bob Nibbled Bens Keish Made Gratefully To Paul
How many bits is in a byte
8
how many bits are in a nibble
4 bits (half a byte)
how many bytes are in a kibibyte
1024
how many bytes are in a mebibyte
1024 x 1024
how many bytes in a gibibyte
1024 x 1024 x 1024
how many bytes in a tebibyte
1024 x 1024 x 1024 x 1024
how do you work out how many mebibytes are in a value
divide it by 1024 x 1024
what is denary
the 10 number base number system (0-9)
what is binary
the 2 number base number system using the digits 0 and 1 and place values 1, 2, 4, 8, 16…
why do we use binary to represent data in computers
becuase anything further would make the data hard to deal with and possibly cause error, it is simpler being one of two values
what is one of the benefits of binary
takes up less storage so it makes computers cheaper and more reliable
what is hexadecimal
the base 16 number system that uses the values 0-9 and A-F
how do you convert a denery number to binary
divide it by 2 and take the answer or remainer and repeat with the answer
Which bit is most significant in binary
the biggest
what does CPU stand for
central processing unit
what does a CPU do
store data in registers
why do overflow errors occur when adding binary
because if the result is greater than 255 then another bit is needed
what makes hexadecimal to binary easier
each value cna be taken into 4 binary bits and then just put the bits together
how do you convert denary to hexadecimal
divide the denary by 16 and then take the remainder and divide the result again
what is a sign bit
when all the other bits of the binary are negative
what is two’s complement
when only the MSB is the negative placeholder
how do you convert nagtive denary numbers into binary using two’s complement
- write the binary as normal
- change the 0 to 1 and 1 to 0
- then add one
What is the affect when binary shifts left
you multiply but the powers of 2
what is the affect when the binary shifts right
you divide by the powers of 2
How many places must you shift the binary left to x2
one
How many places must you shift the binary left to x4
two
How many places must you shift the binary left to x8
three
State some uses of hexadecimal coding
- HTML colour codes
- MAC addresses
why would a programmer prefer hex to binary
- 4 binary numbers = 1 hex
= easier to understand and cheaper
what is the same given to a digit at the end of a sequence of values to calculate an error
check digit
how is a check digit used to detect errors
- value of check digit depends on other digits in sequence
- if any numbers in sequence contain an error, the check digit will be incorrect
how is text represented
each character on the keyboard has a binary value which is transmitted to the computer each time a key is pressed
what is the character set used to represent text in america
ASCII
what is a character set
it contains all the characters that are in that character set andd the binary value that is assigned to each character
what are the two ways sound can be recorded
- analogue
- digital
how is sounds recorded
the amiplitude of the wave must be recorded in regualr intervals - more intervals results in a better quality recording - this is called sound sampling
how is sound stored in a computer
- analogue sounds must be converted to digital to be stored and processed in a computer
- then a digital to audio converter is used to digital signals into outputs
how are images represented
a bitmap is made up of pixels
what is a pixel
a very small dot of colour that is displayed with many more others to create an image
what colour does 1 represeent
white
if more colours represented what happens to the colour(bit) depth
it also increases, as does the file size
how do you calculate the sile size in bytes of an image
(width in px x height in px x colour depth) / 8
what does the desity of pixels affect
the sharpness of an image = smoother edges and better overall quality
what do compression softwares do
use algorithms to remove repeated unneccessary data
what is the purpose of useding data compression
- reduce the size of a file on a disk
- easier for streaming data over the internet
what are the two types of data compression
- lossy
- lossless
what are the file types which use lossy compression
- JPG
- MP3
- WMV
- MPG
what are the benefits and disadvangtages of lossy compression
+ smaller file sizes
+ less transmission time
+ reduces internet traffic
-detail is permanently lost by reducing colour depth, resolution or sample rate
what are the uses of lossy compression
- music streaming
- online images & videos
- image libaries
what file types use lossless compression
- TIF
- GIF
- PNG
- ZIP
what are the benefits and disadvantages of lossless data compression
+ orignal quality is preserved , no information or data lots
-less significant reduction in file size
what are the uses of lossless data compression
- text documents
- electronic books
- high resolution print documents
Explain how sampling is used to store audio recordings
Multiple sound samples are taken in regular intivals to record the sound, the higher the sample rate the better the quatlity of the sound, taking analogue values into digital values for storage
why do computers use binary
because they have memory and NAND gate circuits which uses values of 0 and 1 to locate things out of storage
which number symbolises on
1
which number symbolises off
0
define binary
a base-2 number system that uses the values 0 and 1
what is the benefit of hexadecimal over binary
- hex is easier to read and write
- hex is smaller and takes up less space
- hex is easier to debug and locate errors
what is meant by the term analogue data
a continuous stream of data that is processed by humans
what is meant by the term digital data
discrete data that only uses the values of 0 or 1
can computers process hexadecimal
no
why is A-F used rather than 10-15 in hexadecimal
so only one symbol is needed for the denary number
what us meant by the term ‘MAC address
a unique address that is given to a computer at the manufactoring stage that can be used to identify the computer
give two character sets
- ASCII code
- Unicode
what is meant by the term ‘resolution’
the dimensions of an image (in pixels) it is called metadata
what is meant by the term ‘metadata’
additional data that is stored with an image that con provide information (dimensions, time and data taken)
what is meant by the term ‘colour depth’
the number of bits that are used to create each colour in an image
what is meant by the term ‘lossy compression’
a compression method that reduces the size of a file by permanently removing data
what is meant by the term ‘lossless compression’
a compression method that reduces the size of a file by temporarily alterning the data
explain how a sound file can be compressed
- remove sounds that cannot be heard by the human ear
- remove softer sounds played at the same time as loud sounds
- this is known as perceptual music shaping
what is the process called to compress sound files
perceptual music shaping
