Unit 5

Question 1

Bit

Answer 1

1 or 0

Question 2

Byte

Answer 2

group of 8 bits, 2n different values can be represented with n bits

Question 3

binary units

Answer 3

kibibyte 2^10
mebibyte 2^20
gibibyte 2^30
tebibyte 2^40 bytes

Question 4

ASCII Code

Answer 4

7 bits originally then expanded to 8 bit with Extended ASCII giving an extra 128 values but still only American / Western European alphabets

Question 5

Unicode

Answer 5

originally 16-bit (UTF-16) to allow a greater range of characters to be included then expanded further to 32 bit (UTF-32) to include almost all international alphabets and emojis

Question 6

ASCII und Unicode

Answer 6

same value for any character that exists in both

Question 7

Parity Bit

Answer 7

checks if there are an odd or even number of 1s, uses Most Significant Bit

Question 8

Majority Voting

Answer 8

sends each bit multiple times, majority value is accepted

Question 9

Checksum

Answer 9

hashing algorithm carried out on the data

Question 10

Check Digit

Answer 10

hashing algorithm produces a check digit

Question 11

overflow

Answer 11

is where a number (usually the result of a calculation) is too large to fit into the number of bits available

Question 12

underflow

Answer 12

number too small

Question 13

normalised floating point

Answer 13

consists of mantissa and exponent and always starts with 1.0 or 0.1, can be signed

Question 14

signed binary

Answer 14

most significant bit is negative

Question 15

Resolution

Answer 15

width * height in pixels

Question 16

Colour Depth

Answer 16

number of binary bits per pixel

Question 17

File size

Answer 17

resolution * colour depth

Question 18

Vector Images

Answer 18

the data defining the image is stored in a Drawing List containing the relevant properties

Question 19

Nyquist’s Theorem

Answer 19

the sampling frequency must be at least double that of the highest frequency in the original signal

Question 20

Sound File Size

Answer 20

sample frequency * bit depth * length of sample (multiply by num of chanels)

Question 21

Bit Depth

Answer 21

it’s the number of bits used to record the amplitude at each sample point, also known as sample resolution

Question 22

MIDI

Answer 22

a protocol providing a standard for electrical musical instruments, recording devices, computers to connect and communicate with each other, it carries event messages

Question 23

event messages

Answer 23

-pitch and duration of note
-volume changes
- synchronisation of tempo between classes

Question 24

MIDI file

Answer 24

a list of instructions that tell the controller how to synthesise a sound based on digital sound samples and pre-recordings

Question 25

Data Compression

Answer 25

-Reduces file sizes in a variety of ways depending on type of data -Needed not so much to reduce storage space as memory is cheap but to reduce data transmission time

Question 26

Compression Ratio

Answer 26

compressed file / original file size

Question 27

Lossy

Answer 27

the file is compressed to a smaller size but some data is lost during the process

Question 28

Lossless

Answer 28

reduces a files’ size without losing any data

Question 29

Run Length Encoding (RLE)

Answer 29

repeating data is replaced by a marker, the data and the number of times it is repeated

Question 30

Dictionary-based compression

Answer 30

a dictionary of commonly occurring data is created and referenced, the reference replaces the data and because the reference is shorter than the data itself, file size is reduced

Question 31

Encryption

Answer 31

the transformation of data from one form to another to prevent an unauthorised 3rd party from being able to understand it

Question 32

Plaintext

Answer 32

original text/message

Question 33

Ciphertext

Answer 33

encrypted version of the message

Question 34

Cipher

Answer 34

method or algorithm used to encrypt a message

Question 35

Key

Answer 35

the secret information needed to lock or unlock the message

Question 36

brute force attack

Answer 36

trying everything until it works

Question 37

cryptanalysis

Answer 37

called frequency analysis could be used by looking at the most commonly occurring letter and assuming it is an ‘e’ or other common letter and working from there

Question 38

one-time pad

Answer 38

ciphers with a key that only works once and changes every time you want to access the information