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computer science > data representation > Flashcards

data representation Flashcards

(63 cards)

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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
check digit
Digit calculated using an algorithm and is generated using other digits in a sequence
26
check sum
checks codes for errors during data transmission by calculating the sum of transmitted digits
27
majority voting
Method of checking errors by producing the same data several times and checking if it’s the same each time
28
parity bits
A method of checking binary codes by counting the number of 0s and 1s in code
29
difference in analogue and digital data
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
difference in analogue and digital signal
analogue signals: represented as wave forms Values vary smoothly over time digital signals: represented as binary digits Values are specific and discrete
31
what are ADCs used with
analogue sensors
32
most common use for a DAC
to convert a digital audio signal to an analogue signal
33
Explain the principles of operation of an ADC
The analogue signal is sampled at fixed time intervals
34
bitmaps represented as pixel grid
each pixel corresponds to a single point in the image. The grid is organized in rows and columns
35
bitmaps represented as color depth
The color depth determines the number of bits used to store color information for each pixel.
36
bitmaps represented as Pixel Values
value of each pixel in a bitmap is stored as binary data
37
bitmaps represented as file format
Bitmaps are typically stored in files using specific formats such as BMP PNG, or JPEG
38
resolution
number of dots per inch
39
colour depth
number of bits stored for each pixel
40
resolution of image
size of image
41
calculate storage requirements
size in pixels x colour depth
42
metadata
e.g. width, height, colour depth
43
size of image in pixels
width of image in pixels x height of image in pixels
44
Explain how vector graphics represents images using lists of objects
The properties of each shape in the vector graphic image are stored as a list
45
Give examples of typical properties of objects
co-ordinates fill colour line colour
46
vector graphics approach advantages and disadvantages.
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
bitmapped graphics approach advantages and disadvantages.
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
sample resolution
The number of bits used to represent a single sample
49
sample rate
The number of samples taken per second
50
Nyquist theorem
sampling rate is twice the highest frequency in the original sound
51
Calculate sound sample sizes in bytes
Sample Size (in bytes) = (Bit Depth / 8) * Number of Channels
52
Describe the advantages of using MIDI files for representing music.
More compact Easy to modify
53
Purpose of midi
To easily edit files and exchange data
54
why images and sound files are often compressed
To reduce files which helps streaming or downloading files
55
Advantage and disadvantage of lossless
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
Advantage and disadvantage of lossy
Files are reduced significantly more than lossless but has a loss in quality
57
run length encoding (RLE)
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
dictionary-based methods
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
encryption
Using an algorithm to convert a message into cipher text
60
why it caesar cipher easily cracked
There are only 25 possible keys which comes to process of elimination
61
Explain why Vernam cipher is considered as a cypher with perfect security.
Harder to crack
62
Compare Vernam cipher with ciphers that depend on computational security
Vernam cipher is the only one to be mathematically secure whereas other ciphers can be broken given enough cipher text and time
63
How midi represents music
Musics represented as sequence of instructions Sixteen channels are supported

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