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computer science > data representation > Flashcards

data representation Flashcards

1
Q

use of ordinal number

A

to describe the numerical positions of objects

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2
Q

use of natural number

A

for counting

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3
Q

use for real numbers

A

for measurement

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4
Q

base number for decimal

A

10

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5
Q

base number for binary

A

2

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6
Q

base number for hexadecimal

A

16

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7
Q

pros for hexidecimal

A

more compact
takes less space

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8
Q

bit

A

fundamental unit of information

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9
Q

byte

A

group of 8 bits

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10
Q

binary prefix for kibi, mebi, gibi, tebi

A

kibi, Ki - 2^10
mebi, Mi - 2^20
gibi, Gi - 2^30
tebi, Ti - 2^40

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11
Q

binary prefix for kilo, mega, giga, tera

A

kilo, k - 10^3
mega, M - 10^6
giga, G - 10^9
tera, T - 10^12

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12
Q

difference between unsigned binary and signed binary

A

unsigned: holds only positive numbers

signed: holds positive and negative numbers

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13
Q

the minimum and maximum values for a given number of bits, n fo a unsigned binary

A

0 and 2^n -1

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14
Q

explain why both fixed point and floating point representation of decimal numbers may be inaccurate

A

Rounding errors can occur

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15
Q

Relative Error

e.g. calculate the relative error of 0.94 +- 0.2:

A

(0.2 / 0.94 ) x 100

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16
Q

Absolute Error

A

in 0.94 +- 0.2 , the 0.2 is the absolute error

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17
Q

Compare the advantages and disadvantages of fixed point in terms of range, precision and speed of calculation

A

pros:
Numbers are represented with precision

cons:
Limited range

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18
Q

Compare the advantages and disadvantages of floating point in terms of range, precision and speed of calculation

A

pros:
Provides a large range

cons:
Rounds off large numbers which is time consuming

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19
Q

why are floating point numbers normalised

A

To increase consistency. If each number is represented always by the same bit pattern comparisons would become easier

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20
Q

Overflow

A

When the result of addition or subtraction goes beyond range

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21
Q

Underflow

A

When the result of addition or subtraction is less than the range

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22
Q

Differentiate between the character code representation of a decimal digit and its pure binary representation

A

pure binary representation:
Represents numbers using only 0s and 1s in their binary form

character code representation:
It allows for the representation of decimal digits and characters such as letters, symbols, and control characters

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23
Q

ASCII and unicode

A

Binary coding system for characters and numbers

Binary coding system that includes international characters

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24
Q

explain why Unicode is preferred

A

Unicode can represent characters from different languages around the world

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25
Q

check digit

A

Digit calculated using an algorithm and is generated using other digits in a sequence

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26
Q

check sum

A

checks codes for errors during data transmission by calculating
the sum of transmitted digits

27
Q

majority voting

A

Method of checking errors by producing the same data several times and checking if it’s the same each time

28
Q

parity bits

A

A method of checking binary codes by counting the number of 0s and 1s in code

29
Q

difference in analogue and digital data

A

Analogue is continuous data

Analogue Data:
Represents data using continuous values
Can have an infinite number of possible values

digital data:
Represents data using discrete values
Limited number of possible values

30
Q

difference in analogue and digital signal

A

analogue signals:
represented as wave forms
Values vary smoothly over time

digital signals:
represented as binary digits
Values are specific and discrete

31
Q

what are ADCs used with

A

analogue sensors

32
Q

most common use for a DAC

A

to convert a digital audio signal to an analogue signal

33
Q

Explain the principles of operation of an ADC

A

The analogue signal is sampled at fixed time intervals

34
Q

bitmaps represented as pixel grid

A

each pixel corresponds to a single point in the image. The grid is organized in rows and columns

35
Q

bitmaps represented as color depth

A

The color depth determines the number of bits used to store color information for each pixel.

36
Q

bitmaps represented as Pixel Values

A

value of each pixel in a bitmap is stored as binary data

37
Q

bitmaps represented as file format

A

Bitmaps are typically stored in files using specific formats such as BMP PNG, or JPEG

38
Q

resolution

A

number of dots per inch

39
Q

colour depth

A

number of bits stored for each pixel

40
Q

resolution of image

A

size of image

41
Q

calculate storage requirements

A

size in pixels x colour depth

42
Q

metadata

A

e.g. width, height, colour depth

43
Q

size of image in pixels

A

width of image in pixels x height of image in pixels

44
Q

Explain how vector graphics represents images using lists of objects

A

The properties of each shape in the vector graphic image are stored as a list

45
Q

Give examples of typical properties of objects

A

co-ordinates
fill colour
line colour

46
Q

vector graphics approach advantages and disadvantages.

A

Uses mathematical equations to define shapes and lines

Can be edited and resized easily
Smaller file sizes
Scalable without losing quality

Not suitable for complex and detailed images
Limited in representing continuous-tone images

47
Q

bitmapped graphics approach advantages and disadvantages.

A

Uses a grid of pixels to represent images.

Well-suited for complex and detailed images
Can represent continuous-tone images

Larger file sizes
Not easily scalable without losing quality

48
Q

sample resolution

A

The number of bits used to represent a single sample

49
Q

sample rate

A

The number of samples taken per second

50
Q

Nyquist theorem

A

sampling rate is twice the highest frequency in the original sound

51
Q

Calculate sound sample sizes in bytes

A

Sample Size (in bytes) = (Bit Depth / 8) * Number of Channels

52
Q

Describe the advantages of using MIDI files for representing music.

A

More compact
Easy to modify

53
Q

Purpose of midi

A

To easily edit files and exchange data

54
Q

why images and sound files are often compressed

A

To reduce files which helps streaming or downloading files

55
Q

Advantage and disadvantage of lossless

A

Files can be reproduced exactly as it was in the beginning with no loss in quality but still result in a large file size
No redundant data is lost during the compression process

56
Q

Advantage and disadvantage of lossy

A

Files are reduced significantly more than lossless but has a loss in quality

57
Q

run length encoding (RLE)

A

compresses data by reducing repetitive and consecutive data called runs. Runs of data are stored as a single data value and count rather than the original run

58
Q

dictionary-based methods

A

Variable length strings of data are represented by single tokens
A dictionary is formed using the tokens as the key
The strings of symbols are used as the entries

59
Q

encryption

A

Using an algorithm to convert a message into cipher text

60
Q

why it caesar cipher easily cracked

A

There are only 25 possible keys which comes to process of elimination

61
Q

Explain why Vernam cipher is considered as a cypher with perfect security.

A

Harder to crack

62
Q

Compare Vernam cipher with ciphers that depend on computational security

A

Vernam cipher is the only one to be mathematically secure whereas other ciphers can be broken given enough cipher text and time

63
Q

How midi represents music

A

Musics represented as sequence of instructions

Sixteen channels are supported

computer science (7 decks)

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