3.5 Data Representation

Question 1

Natural Numbers

Answer 1

Numbers used in counting. Any integer greater than or equal to 0.

Question 2

Rational Numbers

Answer 2

Numbers which can be expressed as fractions (includes x/1)

Question 3

Irrational Numbers

Answer 3

Numbers which cannot be expressed as fractions.

Question 4

Real Numbers

Answer 4

The set which contains natural, rational and irrational numbers.

Question 5

Integer numbers

Answer 5

All positive and negative whole numbers

Question 6

Ordinal Numbers

Answer 6

Numbers which describe the positions of things (e.g. first

Question 7

Hexadecimal

Answer 7

Base 16

Question 8

Why Hex?

Answer 8

Easier to represent longer numbers for human interpretation.

Question 9

Binary Prefixes

Answer 9

Kibi, mebi, gibi, etc.

Question 10

Decimal Prefixes

Answer 10

Kilo, mega, giga, etc.

Question 11

Unsigned Binary

Answer 11

Binary that represents positive numbers only

Question 12

Signed Binary

Answer 12

A binary number system that can represent both positive and negative numbers e.g. Two’s Complement Form

Question 13

Two’s Complement

Answer 13

Most significant bit is negative. E.g. for an 8 bit string

Question 14

Converting between decimal and two’s complement

Answer 14

Make the decimal positive (e.g. -9 -> 9), convert to binary, flip the bits and add 1.

Question 15

Converting between two’s complement and decimal

Answer 15

Flip the bits, add 1 then convert.

Question 16

Fixed Point Binary

Answer 16

Allows you to represent fractional numbers in binary.

Question 17

Character set

Answer 17

Set of alphanumeric characters and symbols which can be represented on a computer system.

Question 18

Original ASCII

Answer 18

Character set for English characters and numbers which could only represent 128 characters.

Question 19

Extended ASCII

Answer 19

Character set which uses 8 bits and stores a few more symbols than ASCII

Question 20

Unicode

Answer 20

Character set which uses 16 or 32 bits to support many different characters e.g. Chinese and Emojis.

Question 21

Parity Bits

Answer 21

An additional bit sent along with the rest of the data to ensure it is transmitted correctly.

Question 22

Majority Voting

Answer 22

Each bit is sent an odd number of times (>1). The bit that appears the most out of the set is used.

Question 23

Checksums

Answer 23

Mathematical algorithms applied to each packet of data. If the result of the maths is equal on both ends, the data has been transmitted successfully.

Question 24

Check Digits

Answer 24

Additional digit on the end of a string of numbers. E.g. 13th digit of an ISBN.

Question 25

Resolution (image)

Answer 25

Width pixels x height pixels. Can also be expressed as PPI.

Question 26

Colour Depth

Answer 26

Bits required per pixel. Given as 2^n

Question 27

PPI

Answer 27

Pixels per inch. Describes the density of pixels.

Question 28

Analog to digital converter for sound

Answer 28

Samples amplitude of analogue wave at sample rate times per second.

Question 29

Sample rate

Answer 29

Number of samples taken per second. Measured in Hz.

Question 30

File size of sound

Answer 30

Sample rate x bit depth x duration in seconds

Question 31

Bit depth

Answer 31

Number of bits per sample

Question 32

Nyquist Theorem

Answer 32

Sample rate must be at least double the highest frequency of an original sound for an accurate recording.

Question 33

Continuous data

Answer 33

Data which can be of any numerical value.

Question 34

Discrete data

Answer 34

Data which can only take certain values.

Question 35

MIDI

Answer 35

Allow for electronic musical instruments and computers to communicate. Files are instructions for replication

Question 36

MIDI Contoller

Answer 36

Carry event messages (e.g. pitch)

Question 37

Why compress data?

Answer 37

To save space on storage media or take up less bandwidth during transmission.

Question 38

Lossy compression

Answer 38

All unnecessary info is removed. Smaller file sizes.

Question 39

Lossless compression

Answer 39

All unnecessary info is removed but data to recreate is kept.

Question 40

Run Length Encoding

Answer 40

Consecutive identical data is stored as how many times it occurs, rather than itself on each occurance.

Question 41

Dictionary based compression

Answer 41

Repeating patterns are assigned values and placed into a dictionary and sent along with the main files.

Question 42

Encryption

Answer 42

Prevents unauthorised people from reading data.

Question 43

Encryption key

Answer 43

Information needed to decipher the encrypted data.

Question 44

Caesar cipher

Answer 44

Shift each letter by x number of characters where x is the key.

Question 45

Vernam Cipher

Answer 45

Uses a one time pad XORd with its corresponding character in the plaintext. Perfect security as OTP must be destroyed after use.

Question 46

Image size

Answer 46

Dimensions x Colour Depth