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A Level AQA Computer Science > Data representation > Flashcards

Flashcards in Data representation Deck (41)
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1

what is a rational number?

any value expressed as a ratio or fraction.

2

what is a irrational number?

can't be express as a fraction has endless series of digits and rounding would cause a rounding error. e.g Pi.

3

what is a Ordinal numbers?

rating or ranking like first second numbers.

4

how do you convert between decimal to binary?

divide the decimal by 2 because binary use base 2.

5

how do you convert binary to hexadecimal?

uses nibble 4 bits 2 sets not 8 bits and only add the 1's that can't go above 8 decimal.

6

how to convert hexadecimal to decimal?

16 x the first hex digit and 1 x the second digit add together = decimal.

7

how to convert decimal to hexadecimal?

divide decimal by 16 get first digit and remainder becomes second one.

8

why is hexadecimal used?

Less likely to write a mistake, easy to remember, quicker to write, define colours and is easy to convert.

9

what is gibi/Giga 2 to the power of?

30

10

how many combinations does ASCII 7 bit use?

128

11

how many bits does Unicode use?

16

12

what is a parity bit?

A bit used to check errors by making the 1's add up to even or odd depending on the parity bit and is found at the start of line of binary.

13

what is majority voting?

sends each bit three times so if one is flipped it takes the bit what is in majority as the correct number.

14

How does binary addition work?

Add bits together right to left one bit from each line

15

How do you multiply binary by 2

Add a 0 to the end

16

How would you multiply binary in general?

Line binary one above other and for each bit on second line times it by the bit above each of first line. So for the first bit in second line you should have a line under it. Do this again for second bit but add a 0 to the start and 2 0 to the 3 red bit on second line then add the lines of bits you create together

17

what is a real number?

a rational or irrational number used for measuring.

18

how many combinations does ASCII 8 bit use?

255

19

what can cause errors transmission?

Electrical interference, power surge, synchronisation issues and wear and tear on cables

20

what is check digit?

An extra digit at the end of string of digit used in bar-codes.

To complicated to explain here i suggest you look how to work it out.

21

what is checksum and how does it work?

Total sum of all bytes add up sent with data and is check other side if data matches the checksum.

22

how does two's complement work?

Flip all the bits in the even of that number and add one to the end.

23

What is two's complement used for?

to ensure that subtraction occurs when adding negative numbers.

24

when representing a fraction in binary what 4 fraction do you use to represent the digits after the decimal point ?

1/2, 1/4 , 1/8, 1/16. think of after decimal it's 2 to the power of -1 and so on.

25

what is a pixel?

The smallest value of colour that can be displayed.

26

define resolution?

The number of pixels contained in any graphic.

27

how is resolution calculated?

width x height in pixels.

28

when a image is made bigger are there more pixels or are the pixels just bigger?

They only get bigger.

29

what is bit colour depth?

The number of bits that represents one pixel.

30

how do you calculate image file size?

resolution x bit depth / 8 (8 bits in a byte).

31

what is metadata?

data about data e.g when it was made the bit depth.

32

name a analogue to digital converter?

microphone.

33

how are analogue sounds recorded?

Amplifier.

34

In sampling amplitude is referred to as?

sample resolution.

35

what is sampling rate and what is it measured in?

samples taken per second.

36

what is sampling?

when you record a sound by only recording it at specific time.

37

what is sample resolution?

the number of bits used to record each sample.

38

how does sample rate affect the sound?

bigger sample rate better quality.

39

how do you work out the file length of a sound file?

sample rate x resolution x length in seconds.

40

How big does the sample rate have to be to record the sound accurately?

double the size of the highest frequency because sound is made of many waves of sound with different frequency.

41

what is human hearing range?

20Hz to 20kHz.