Fundamentals of Data Representation

Question 1

Natural Numbers

Answer 1

The set of positive integers and 0. A subset of Integer Numbers.

Question 2

Integer Numbers

Answer 2

The set of numbers with no fractional part.

Question 3

Rational Numbers

Answer 3

The set of numbers that can be represented as the ratio of two integers.

Question 4

Irrational numbers

Answer 4

The set of numbers which cannot be represented as a ratio of two integers.

Question 5

Ordinal Numbers

Answer 5

Natural numbers used to describe numerical position or order of objects

Question 6

Binary

Answer 6

A number system with base 2.

Question 7

Decimal

Answer 7

A number system with base 10.

Question 8

Hexadecimal

Answer 8

A number system with base 16

Question 9

Number base

Answer 9

The number of unique digits used by a particular number system to represent numbers.

Question 10

Bit

Answer 10

A binary digit used by computers as the fundamental unit of information. Either 1 or 0.

Question 11

Byte

Answer 11

A group of 8 bits

Question 12

Nibble

Answer 12

A group of 4 bits

Question 13

Binary prefix

Answer 13

A prefix to a unit representing a power of 2. Kibi = power of 10, Mebi = 20, Gibi= 30, Tebi = 40

Question 14

Decimal Prefix

Answer 14

A prefix to a unit representing a power of 10

Question 15

Signed binary

Answer 15

A binary system capable of representing negative and positive numbers

Question 16

Unsigned binary

Answer 16

A binary system that can only represent positive numbers.

Question 17

Two’s complement

Answer 17

Coding scheme used to represent negative or positive number. If most significant bit is 1 = negative

Question 18

Exponent

Answer 18

Stores number of positions to move the decimal point

Question 19

Fixed point form

Answer 19

Decimal point is at a fixed position.

Question 20

Floating point form

Answer 20

Radix point moved by exponant and uses normalisation. Number before and after decimal point have to be opposite. ie 1.0… or 0.1…

Question 21

Mantissa

Answer 21

Component of floating point that stores the significant figures of the floating point

Question 22

Absolute error

Answer 22

Difference between correct value and rounded value (ie stored in binary)

Question 23

Relative error

Answer 23

The percentage difference between the exact value and rounded value

Question 24

Underflow

Answer 24

The misrepresentation of a numeric value because it is too small to be represented by allocated exponent.

Question 25

Overflow

Answer 25

Incapability to store a number in assigned bits because it is too large

Question 26

Character code

Answer 26

A unique binary representation of a character

Question 27

ASCII

Answer 27

character set used to represent alphanumerical values or symbols as a set of 8 bits (used to be 7)

Question 28

Unicode

Answer 28

Superset of ASCII. Uses 16 or 32 bits instead of 8, where first 8 bits are the same symbols as in ASCII, 32 bits includes thigs such as chinese characters. Good for multilingual data. Needs much more storage space and higher transmission time than ASCII.

Question 29

Check digit

Answer 29

Method of error checking during data transmission by adding an extra digit at the end calculated from digits in code itself, usually mod 10.

Question 30

Check sum

Answer 30

Checks for transmission errors by calculating sum of transmitted digits

Question 31

Majority voting

Answer 31

Sending each bit thrice and then taking majority as correct digit. Error checking and correction during transmission.

Question 32

Parity bits

Answer 32

Most significant bit used to make number of 1's sent in data packet either even or odd.

Question 33

Bitmapped Graphics

Answer 33

Image composed of an array of pixels with allocated number of bits arranged to form an image.

Question 34

Bitmap resolution/Size

Answer 34

Width in pixels * height in pixels

Question 35

Bitmap storage requirements

Answer 35

Amount of storage required for image = bitmap resolution * colour depth

Question 36

Colour depth

Answer 36

Number of bits per pixel where n bits can store 2^n colours

Question 37

Metadata

Answer 37

Data related to image file itself ie pixel width, depth, location

Question 38

Bitmap Density

Answer 38

Number of pixels per inch, used to describe computer screen

Question 39

Vector image

Answer 39

stores image as drawing list instead of pixels, can be scaled up without loss of detail, needs less storage space unless many tiny details.

Question 40

Image manipulation

Answer 40

You can change individual pixels easily in bitmap images and individual objects but not pixels in vector images

Question 41

Sound conversion to digital

Answer 41

Continuous analogue data converted to discrete digital data format where sampling frequency is measured in Hertz

Question 42

Sampling rate

Answer 42

The frequency at which you record the amplitude of the sound, higher sampling rate equals smoother sounding playback, however needs a lot of storage

Question 43

Sample size

Answer 43

num of bits per sec * length of recording in sec * num of bits per sample

Question 44

Analogue data

Answer 44

Analogue technology records wave in original format, for ex signal in microscope can be copied onto tape, read, amplified and sent to a speaker, quantities are measured

Question 45

Digital signal

Answer 45

Digital technology samples analogue waveforms in intervals and stores it on a digital device, quantities rather counted than measured

Question 46

Analogue to digital

Answer 46

Microphone turns sound energy into electrical energy, ADC samples data and turns it into binary

Question 47

Digital to Analogue

Answer 47

DAC converts binary back into a sound wave which then gets amplified which is connected to a speaker

Question 48

Interpreting frequency

Answer 48

Higher frequency means higher pitch and vise versa

Question 49

Nyquist theorem

Answer 49

Sampling rate should be at least double of the maximum frequency in original analogue signal

Question 50

Sound sampling

Answer 50

The process of converting analogue sound waves to a digital waveform

Question 51

Midi controller

Answer 51

Musical digital Instrument interface is a protocol for ADC audio transmission to a digital interface used for the majority of electronical musical instruments and computers

Question 52

Event messages

Answer 52

Bidary data transmitted between midi device and computer processor that carries properties controlling when and how sound is produced

Question 53

lossy compression

Answer 53

Removes non-essential information, data loss is non-recoverable

Question 54

lossless compression

Answer 54

records patterns of data instead of actual data, no data is lost

Question 55

Run-Length encoding

Answer 55

A type of lossless compression where repeated occurrences of the same data re stored as single data values with their counts

Question 56

Dictionary based encoding

Answer 56

Lossless compression where often reoccurring words are stored in dictionary and those words in the text replaced with the dictionary code

Question 57

Encryption

Answer 57

process of converting original data (plaintext) into a form which cannot be understood by unauthorised users (ciphertext) using an encryption algorithm (cipher)

Question 58

Caeser cipher

Answer 58

shifts alphabet and number shifted by is the key

Question 59

Vernam Cipher

Answer 59

Chiper that uses a one time pad to convert each each character to cipher text, computationally secure, uses XOR

Question 60

Brute force attack

Answer 60

Try until code has been deciphered

Question 61

Cryptanalysis

Answer 61

Uses for example frequency analysis to decode a cipher

Question 62

One time pad

Answer 62

A secret random key which is only used once

Question 63

Computationally secure

Answer 63

When time needed to decipher a code is unreasonable for data encrypted