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Computer Science Flashcards > 1. Data representation > Flashcards

1. Data representation Flashcards

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1
Q

Define a bit

A

The basic computing element that is either 0 or 1

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2
Q

Define the binary number system

A

A number system based on 2 and can only use values 0 and 1

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3
Q

Define an error code

A

It is an error message generated by the computer

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4
Q

Define a MAC address

A

It is an address (given in hexadecimal) that uniquely identifies a device on the internet in the form of NN-NN-NN-DD-DD-DD

(NN-NN-NN is the manufacturer code)

(DD-DD-DD is the device code)

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5
Q

Define an IP address

A

It is an address that uniquely identifies each device connected to a network identifying their location.

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6
Q

Define HTML

A

It is used to design and write webpages

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7
Q

Define an overflow error

A

The result of doing a calculation that produces a value that is too big for the computers allocated word size

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8
Q

Define logical shift

A

An operation that shifts bits to the left or right in a register.

(Any bits shifted out of the register are replaced with zeroes)

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9
Q

Define the two’s complement

A

A method of representing of negative numbers in binary

(When applied to an 8-bit system, the left most bit is given the value -128

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10
Q

What is an ASCII code

A

A character set for all the characters on a standard keyboard and control codes.

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11
Q

Define a character set

A

a list of characters that have been defined by computer hardware and software.

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12
Q

Define an Unicode

A

a character set which represents all the languages of the world

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13
Q

Define a sampling resolution

A

the number of bits used to represent sound amplitude in digital sound recording

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14
Q

Define what is bit depth

A

the number of bits used to represent the smallest unit in a sound file

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15
Q

Define what is color depth

A

the number of bits used to represent the colours of a pixel

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16
Q

Define sampling rate

A

the number of sound samples taken per second in digital sound recording

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17
Q

Define bitmap image

A

an image made up of pixels

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18
Q

Define pixel

A

the smallest element used to make up an image on a display

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19
Q

Define image resolution

A

the number of pixels in the X–Y direction of an image,

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20
Q

Define pixelated image

A

this is the result of zooming into a bitmap image; on zooming out the pixel density can be diminished to such a degree that the actual pixels themselves can be seen

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21
Q

Define pixel density

A

number of pixels per square inch

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22
Q

Define compression

A

reduction of the size of a file by removing repeated or redundant pieces of data;

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23
Q

Define bandwidth

A

the maximum rate of transfer of data across a network, measured in kilobits per second (kbps) or megabits per second (Mbps)

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24
Q

Define lossy file compression

A

a file compression method in which parts of the original file cannot be recovered during the decompression process

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25
Q

Define lossless file compression

A

A file compression method that allows the original file to be fully restored during the decompression process, for example, run length encoding (RLE)

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26
Q

Define audio compression

A

a method used to reduce the size of a sound file using perceptual music shaping

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27
Q

Define MP3

A

a lossy file compression method used for music files

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28
Q

Define MP4

A

a lossy file compression method used for multimedia files

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29
Q

Define JPEG

A

; a form of lossy file compression used with image files which relies on the inability of the human eye to distinguish certain colour changes and hues

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30
Q

Define RLE

A

a lossless file compression technique used to reduce the size of text and photo files in particular

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31
Q

How do you calculate The file size of an image

A

image resolution (in pixels) × colour depth (in bits)

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32
Q

How do you calculate The size of a mono sound file

A

sample rate (in Hz) × sample resolution (in bits) × length of sample (in seconds)

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33
Q

Why is file compression necessary

A

» to save storage space on devices such as the hard disk drive/solid state drive

» to reduce the time taken to stream a music or video file

» to reduce the time taken to upload, download or transfer a file across a network

» the download/upload process uses up network bandwidth

» reduced file size also reduces costs.

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34
Q

Define a data packet

A

a small part of a message/data that is transmitted over a network

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35
Q

Define a data packet

A

a small part of a message/data that is transmitted over a network

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36
Q

What is the building block of all computers and why

A

What do switches in a computer do and what is another name for themBinary number system, because it is only made up of 0’s and 1’s. Computers contain millions of tiny switches that must be in either the ON or OFF position. These positions can be represented by the binary number system.
1=ON(high)
0=OFF(low)

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37
Q

What do switches in a computer do and what is another name for them

A

Make use of logic gates and store and process data
Microtransistors

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38
Q

What does binary allow computers to do

A

Carry out calculations

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39
Q

What is a bit

A

A basic computing element that is either a 0 or 1, comes from BInary digiT

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40
Q

What is the binary number system

A

A number system based on 2, and only contains 0’s and 1’s

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41
Q

What is the denary system also called

A

A base 10 number system

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42
Q

What are the uses of the hexadecimal system

A

Error codes
Mac address
IPv6 adress
HTML colour codes

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43
Q

What are error codes

A

They are codes that are usually automatically generated, and refer to the memory location of the error

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44
Q

What does the MAC address stand for

A

Media Access Control address

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45
Q

What does NIC stand for

A

Network interface card

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46
Q

What is a MAC address

A

A number which uniquely identifies a device on a network, it refers to the NIC.

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47
Q

Why are MAC addresses rarely changed

A

So that a particular device can always be identified no matter where it is

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48
Q

What does the NN-NN-NN in a MAC address identify
What does the DD-DD-DD in a MAC address identify

A

The number of the manufacturer
The device serial number

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49
Q

What do IP addresses stand for

A

Internet protocol addresses

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50
Q

What is the difference between an IPv4 and an IPv6

A

32 vs 128 bit number. IPv6 uses a colon instead of a decimal point

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51
Q

What does HTML colour codes stand for

A

Hyper text markup language colour codes

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52
Q

Why is the maximum denary value of an 8-bit binary number

A

255
(2^8-1)

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53
Q

What is it called when there is more than 8 bits generated after calculations and what does it mean

A

Over flow
The number is too big to be stored in the computer using 8 bits
A bigger register needs to be used

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54
Q

What is an overflow error

A

The result of carrying out a calculation where the result is too big for the computers word size.

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55
Q

What is hexadecimal

A

A number system based on 16, goes from 0-9 and then A-F

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56
Q

What is HTML

A

It is a mark-up (NOT PROGRAMMING) language used when writing and developing web pages
It uses tags<>
Often represents colours of text on screen

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57
Q

What is a logical shift

A

An operation that shifts buts left/right in a register and replaces shifted bits with 0
Left shift= multiply binary number by 2
Right shift=divide binary number by 2

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58
Q

What is the left most bit reffered to as

A

The most significant bit

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59
Q

What does ASCII code stand for and what is it
What was it originally used for

A

American Code for Information Interchange
It is a set of characters for each character on a standard keyboard/control code.
Communication and computer systems

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60
Q

What is a character set

A

A set of characters that have been defined by computers hardware and software. It is used so that the computer can understand human characters.

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61
Q

What does the standard ASCII code character set consist of and what is it used for

A

7-bit codes(0-127 in denary/00to 7F in hex)
Represent the letters numbers and characters found on a standard keyboard together with 32 control codes(0-31 denary, 00 to 19 hex)

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62
Q

What does ASCII vs unicode use to represent a character

A

1 vs 4 bytes

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63
Q

What were the goals of unicode (5)

A

To have uniform code
Unambiguous code
Reserve part of the code for private use
Universal standard
More efficient coding system

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64
Q

What is unicode

A

Character set that represents the languages of the world (first 128 are the same as ASCII)

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65
Q

What does the aplitude of a wave specify

A

The loudness of the sound

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66
Q

What is analouge data

A

Data that varies continuously

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67
Q

How do computers store sound wave data

A

They convert it from anolouge to digital using an ADC, sampling the amplitude at regular intervals. The amplitude cannot be precicely measured so approximate values are stored.

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68
Q

How could you get a more accurately sampled sound

A

By increasing the sampling resolution(bit depth)

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69
Q

What is sampling resolution

A

Also known as bit depth
The number of bits used to represent sound amplitude in a digital recording

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70
Q

What is bit depth

A

The number of bits used to represent the smallest unit in a sound file

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71
Q

What is the sampling rate

A

The number of sound samples taken per second
Measured in hertz where 1 herts means one sample per second

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72
Q

How is sampling used to record a clip (3)

A

The amplitude is first determined at set time intervals
An approximate representation of the wave is produced
Each sample is then encoded to a series of binary digits

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73
Q

What are the advantages of a higher sample rate/larger resolution

A

Larger dynamic range
Less sound distortion
Better sound quality

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74
Q

What are the disadvantages of a higher sample rate/larger resolution

A

Produces larger file size
Takes longer to transmit/download
Requires a greater processing power

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75
Q

What is a bitmap image

A

An image made up of pixels

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76
Q

What is colour depth

A

The number of bits used to represent the colours of a pixel

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77
Q

What is an image made up of

A

A two-dimentional matrix of pixels

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78
Q

What bit depth do modern computers have

A

24 bit depth

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79
Q

What is image resolution

A

The number of pixels that make up an image

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80
Q

Explain the drawbacks of high resolution images

A

They increase file sizes, which impacts how many images can be stored on the eg. Hardrive. It takes longer to download and transfer the images.

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81
Q

what is pixel density

A

The number of pixels per square inch

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82
Q

How big is a byte

A

8 bits

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83
Q

How big is a nibble

A

4 bytes

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84
Q

What is the largest memory size metioned in the textbook

A

Exabyte
X10^18

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85
Q

What is a more accurate way of measuring memory sizes, and what should be measured using this

A

IEC memory size system
International electronical commision
RAM and ROM

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86
Q

Why would data need to be compressed

A

Storage
Time taken to stream
Reduce file size=reduce costs
Reduce time to download/transmit
Reduce bandwidth usage

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87
Q

What is bandwidth

A

Where maximum rate of data transfer accross a network measured in kbps or mbps

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88
Q

What is lossy file compression
Eg.

A

A compression process that eliminates unneccesary date and some detail which cannot be recovered during the decompression process
JPG
MP3
MP4

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89
Q

How does lossy file compression affect MP3 (2)

A

It removes sounds out of the human hearing range
If there are 2 sounds at the same time, one is removed

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90
Q

What is audio compression

A

A method used to reduce the size ofa sound file using perceptual music shaping

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91
Q

What is the difference between MP3 and MP4 files

A

MP3 is for music
MP4 allows multimedia storage.

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92
Q

What is the JPEG file reduction process based on

A

Human eyes dont detect differences in colour as well as they do differences in brightness
By separating pixel colour from brightness, images can be split into 8x8 pixel blocks which allows information to be easily discarded with minimal quality loss

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93
Q

When should lossless file compression be used

A

When comressing large/complex spreadsheets or downloading a large computer application

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94
Q

What is RLE and what does it do

A

Run-length encoding
Form of lossless file compression
Reduces size of a string of adjacent,identicsl data
This string is then encoded into 2 values, the first being the number of identical items in the run, the second the code of the data (eg. ASCII)
Only effective if there are long runs of repeated bits

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95
Q

Order and power of storage (bits)

A

2^1 bits, 2^2 nibbles, 2^3 bytes, 2^10 KB, 2^20 MB, 2^30 GB, 2^40 TB, 2^50PB

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96
Q

Storage for 1 ASCII character

A

1 byte

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97
Q

Storage for 1 UNICODE character

A

2 bytes

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98
Q

Hexadecimal base, characters and uses

A

Base 16, 0-9 then A-F, MAC Addresses/Html colour coding and computer error messages, IPV6 messages

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99
Q

How is data stored on a computer

A

In binary using 1s and 0s, on or off

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100
Q

What is a bitmap image

A

Bitmap (raster) images are comprised of small picture elements called pixels. Bitmaps blur when enlarged

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101
Q

What is a vector image

A

Vector images use mathematical expressions to describe how the image is created and do not blur when enlarged

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102
Q

JPG or JPEG images

A

JPG or JPEG is a type of bitmap image that has been compressed using lossy compression. When the image is enlarged it appears blurry.

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103
Q

Calculating bitmap file size

A

pixels down x pixels across x bit depth
divide answer by 8 to give in bytes
divide by 1024 if more than to give in KB
and so on till PB

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104
Q

Sound stored on a computer

A

Humans hear sound as analogue data that varies over time though computers work with digital data. Computers sample the sound at difference time intervals to best recreate it.

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105
Q

Sound sample rate

A

The more samples per time interval the better the quality of sound

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106
Q

Sound file size calculation

A

frequency (sample rate/hertz) x bit depth x length x channels

channels:
stereo is 2
5.1 is 6
7.1 is 8

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107
Q

Lossy compression of sound file

A

In an MP3 file lossy compression works by removing frequencies humans can’t hear well and/or at all

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108
Q

MIDI files

A

MIDI files don’t contain music or sounds, they contain a list of commands that instruct a device on what sound to produce, how loud, what frequency and for how long.

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109
Q

Video file storage

A

MP4 files allow for multimedia, sound and picture

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110
Q

Uses of lossy compression

A

audio, video, images

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111
Q

Lossless compression uses

A

text

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112
Q

Binary systems

A

Computer uses binary. Has transistors which have 1s and 0s which are located in the integrated circuits.

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113
Q

Hexadecimal uses

A

Memory dumps
Represent colour in HTML
MAC Addresses
URL
Assembly language
IPv6 Addresses
Locations in memory

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114
Q

MAC Address structure composed of

A

NN-NN-NN-DD-DD-DD

First part is the organisationally unique identifier (OUI) or the manufacturer ID

Next is universally administered address (UAA) serial number

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115
Q

Describe MIDI File

A

Musical Instrument Digital Interface
Stores a set of notes
Does not store actual sounds
Data in file recorded using digital instruments
Sends file to audio synthesiser to play note
Specifies when each note plays and stops, duration, tempo, instrument type
Individual notes can be edited

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116
Q

Describe JPEG

A

Joint photographic experts group
Standard format for storing lossy compression image
Maintain decent img quality
File size = pixels * primary Color’s

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117
Q

Describe MP3

A

Format for digital audio
Actual recording of the sound
Is a lossy compression format
Recorded using microphone

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118
Q

Describe MP4

A

It can store multimedia
Music, videos, text, photos
Format of lossy compression

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119
Q

Describe Parity Check and its limitations

A

Method of data transmission
System could use odd or even parity
Odd/Even parity is decided and parity bit is added at the end
When receiver gets data a check is performed
Bits are counted
If incorrect data sent repeatedly till server times out

Limitations:

Transposition error
When bits still add up to odd/even number
Even number of incorrect bits

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120
Q

Describe ARQ

A

Transmitter sends data in packets
When received it is checked for errors
If no errors, sends an acknowledgment
If no acknowledgment received, it sends it repeatedly
Till server times out

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121
Q

Describe check digit

A

Data is input with check digit
Calculation performed on inputted data
Calculated digit is then compared to a stores value
If it matches, data entered is correct
If no match, data entered is incorrect

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122
Q

Describe check sum

A

Transmitter sums up total group of data before transmission
Data is sent along with the sum
Receiver works out sum and compares to stored value from transmitter
Data should match meaning it’s correct
If no match data entered is incorrect

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123
Q

Memory ascending order

A

Small - Large

Bit
Nibble = 4 bits
Byte = 8 bits
Kilobyte = 1000 bytes
Megabyte = 1000 kilobytes
Gigabyte = 1000 megabytes
Terabyte - 1000 gigabytes

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124
Q

Describe Lossy compression

A

A compression algorithm used
Data will be lost permanently
Reduce colour depth
Reduce number of pixels
Reduce sample rate
Use perceptual music shaping (removes inaudible sounds)

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125
Q

Describe Lossless compression

A

Compression algorithm
No data will be removed permanently
For example an RLE algorithm may be used
Repeated patterns are identified and indexed
Sometimes replaced

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126
Q

Describe Bitmap img

A

Stores position and colour of every pixel
Very detailed images used for photos
Makes them large files
If compression resolution decreased
Uses .bmp file

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127
Q

Describe Vector img

A

Mathematically constructed image
Uses math formulas to draw shapes and lines
Results in small file size
Uses .svg file
Good for cartoons unaffected by pixelation

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128
Q

Why is Lossy better than Lossless

A

− Lossy decreases the file size more
− Take up less storage space on webserver/users’ computer
− Quicker to upload/download
− May not need to be high quality
− Website will load faster for users
− Less lag/buffering when watching
− Takes up less bandwidth to download/upload
− Uses less data allowance

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129
Q

Why is Lossless better than Lossy

A

− Image if compressed does not become pixelated
− User has the option retain all original data
− Can restore the compressed image into original
− Also reduces file size to an extent

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130
Q

uses of binary system (3)

A

ASCII value
unicode value
instruction

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131
Q

memory measurements from smallest to largest (5)

A

1KB
1MB
1GB
1TB
1PB

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132
Q

advantages of using hexadecimal (5)

A

easier to understand
easier to debug
shorter so takes up less space
faster to enter than binary
conversion to binary is easier than from denary

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133
Q

uses of hexadecimal numbers (3)

A

MAC address
HTML colours
error messages

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134
Q

problems with shifting bits (3)

A

may run out of places at the end of the register
end bit may be lost
may result in loss of precision

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135
Q

what does HTML stand for

A

hyper text markup language

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136
Q

structure of HTML

A

structure used for layout
in HTML doc, presentation and structure often kept separate
HTML tag used for structure

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137
Q

URL (composed of 3 parts)

A

protocol
filename
webserver name

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138
Q

presentation of HTML

A

presentation used for colour/style
in HTML doc, presentation and structure often kept separate
CSS linked to the HTML used for presentation

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139
Q

what does MAC address stand for

A

Media access code

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140
Q

explain what is meant by a MAC address (6)

A

hardware address
unique num associated w device
LAA
UAA
first 6/8 digit = manufacturer code
last 6/8 digit = serial num of device

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141
Q

What is the denary system?

A

Number system based on the number 10

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142
Q

What is the binary system?

A

Number system based on the number 2

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143
Q

What is the hexadecimal system?

A

Number system based on the number 6

Used for memory dumps, HTML, MAC addresses, web addresses and assembly code/machine code

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144
Q

How do you convert from binary to denary?

A

Add the powers above the binary number, add up the binary numbers where the 1s appear

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145
Q

How do you convert from denary to binary?

A

Under powers, add 1s from right to left if it can add to the number

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146
Q

How do you convert from memory sizes?

A

add / divide by 1024

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147
Q

How do you convert from binary to hexadecimal?

A

convert each group of 4 binary digits to a hex value

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148
Q

How do you convert hexadecimal numbers to binary?

A

convert each letter/number into 4-bit binary

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149
Q

How do you convert hexadecimal numbers to denary?

A

Remember the place values and then multiply the hex number by this

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150
Q

How do you convert denary numbers into hexadecimal numbers?

A

convert from denary to binary to hexadecimal

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151
Q

How is hexadecimal used for memory dumps?

A

allows the contents of the memory to be seen by the writer when developing new software
enabling errors to be detected
also used in diagnostics when a computer malfunction (hex used as it is easier to use than a long string of binary values)

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152
Q

What is HTML used for?

A

hypertext markup language used for when writing and developing web pages (uses tags)

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153
Q

What is MAC addresses used for?

A

to uniquely identify a device on the internet (can be UAA or LAA)
first 6 digits for manufacturer code

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154
Q

How is hexadecimal used for web addresses?

A

ASCII codes can replace the URL (which are hex values)

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155
Q

How is hexadecimal used for assembly code / machine code?

A

makes it easier, faster and less error-prone in writing the code in binary

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156
Q

What are the Number Systems and their Bases?

A

Binary, Base 2
Denary, Base 10
Hexademical, Base 16

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157
Q

What is Binary?

A

Binary is a base 2 number system, having the digits 0 and 1 - which represent true and false, as well as voltage levels.

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158
Q

What is a bit?

A

A bit is the fundamental unit, 0 or 1.

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159
Q

What is the hierarchy of units in binary?

A

Bit → 1/0

Nibble → 4 Bits

Byte → 8 Bits.

Kibibytes → 1024 Bytes

Mebibyte → 1024 Kibibytes

Gibibyte → 1024 Mebibytes

Tebibyte → 1024 Gibibytes

Pebibyte → 1024 Tebibytes

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160
Q

What are the titles for the most left bit and the most right bit?

A

Most Left → Most Significant Bit
Most Right → Least Significant Bit

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161
Q

What is Signed Binary?

A

Signed Binary are binary values of positive and negative, containing 2 variables of Sign and Magnitude.

Signed binary has a Sign Bit, which is the MSB, at 1 it is negative, and at 0 it is positive.

It cannot be used to processing zeroes, because zero cannot be positive or negative.

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162
Q

What are the possible textual representations?

A

ASCII
Unicode

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163
Q

What is ASCII?

A

ASCII contains characters encoded with character sets → codes assigned to a character.

Originally only 7 bits long, but extended to 8 to contain 256 characters.

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164
Q

What is Unicode?

A

Unicode was created due to ASCII’s inability to represent all possible characters.

ASCII is a subset of Unicode, Unicode uses 16 bits, having codes for 120 000 characters.

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165
Q

What are encoding tables?

A

Character codes are sequential, so it is in ascending order. To find the code for another character, simply add to where a previous one is.

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166
Q

What is a pixel?

A

The smallest distinguishable feature.

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167
Q

How are images represented in binary?

A

Bitmaps, images are stored as an array of individual pixels.

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168
Q

How do you calculate an image’s size?

A

Pixel Width x Height

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169
Q

What is the resolution of an image?

A

It is the detail that an image holds, aka pixels per inch.

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170
Q

How is an image converted from analogue to digital?

A

A grid is placed over the image
An average colour is found for each pixel and assigned a binary value
Each pixel is represented by multiple bits, one combination a shade
The number of bits in a pixel is called the colour/bit depth.

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171
Q

What affects an image’s size?

A

Increasing Resolution; Increasing Colour Depth

Size = Pixel Size x Colour Depth (in bits)

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172
Q

What is Metadata?

A

It is data about data, for example it allows the image to be displayed properly as well as other unneeded data:

File name; format; colour depth; resolution; camera details

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173
Q

What is the difference between analogue and digital data?

A

Analogue signals are continuous, represented by waves.

Digital data is discrete, falling between defined ranges and taking only certain values.

Computers require digital data, as it cannot read analogue signals.

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174
Q

What is a sampling frequency?

A

It is the number of samples obtained over second, measured in hertz. The greater the sampling frequency, the better quality but the larger file.

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175
Q

How is sound digitized?

A

Several samples should be taken at regular intervals, with a binary value given to each reading

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176
Q

What is a sample size?

A

It is the bit depth

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177
Q

What is the bit rate?

A

It is the number of bits used per second

Bit rate = Sampling Frequency x Sample Size

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178
Q

How is a sound file size calculated?

A

It is the Sampling Frequency x Sample Size x Time

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179
Q

What is Compression and the Two Types of it?

A

Compression is the reduction of file size without losing important information.

Lossy
Lossless

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180
Q

What is Lossy Compression?

A

Lossy compression is a means of compression in which data is removed and lost forever. Some quality can be lost.

E.g JPEG, MP3, MP4

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181
Q

What is Lossless Compression?

A

No data is removed here - it is maintained, but it is rearranged, for example using Run Length Encoding.

Repeated data is replaced with frequency
The more data the more the file can be compressed
Can be restored fully

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182
Q

What is Encryption?

A

It is the process of making data secret so only authorised viewers can decrypt and read the data.

It doesn’t prevent interception, it simply stops it from being understood.

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183
Q

What is the simplest process of Encryption?

A

Plaintext → Ciphertext → Message Sent → Message Received → Message Decrypted

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184
Q

Why is Encription Required?

A

It is needed to protect data, especially important ones
Bank information, government details, identity information

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185
Q

What are the uses of hexadecimal

A

Memory dumps (B 5 A 4 1 A F C)
Html color code (#FF 00 00 - red)
Mac address (00-1C-B3-4F-25-FE)
Web address
Assembly language
Error messages
Locations in memory

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186
Q

Reasons for using hexadecimal

A

Easier for humans to read/ write/understand
Easier to remember for humans
easier to debug
Fewer errors made
Shorter way to represent data
takes up less space on screen

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187
Q

Reasons to use binary

A

Computer uses logic circuits

These can only process 1s and 0s

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188
Q

Describe html presentation

A

formatting/style
Separate file/CSS used
E.g background color
Color applied to text
Font style

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189
Q

Describe html structure

A

Layout of webpage
Uses tags to define it
Eg where paragraph is placed
Where images is placed

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190
Q

How many GiB in a TiB?

A

1024 GiB

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191
Q

How many MiB in a GiB?

A

1024 MiB

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192
Q

What are the uses of hexadecimal?

A

Colour values in photo editing software
MAC addresses
IPv6 addresses
Unicode

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193
Q

What is an overflow error?

A

A computer or a device has a predefined limit that it can represent or store (e.g. 32 bits).
Once a values falls outside this limit, an overflow error occurs

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194
Q

How to convert using a Two’s Complement Signed Integer?

A

Flip the bits and add 1

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195
Q

What is a character set?

A

Consists of all the letters, numbers and special characters that can be recognised by a computer system.

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196
Q

How many characters/bits does the ASCII character set use?

A

128 characters / 7 bits

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197
Q

How many characters/bits does the Extended ASCII character set use?

A

256 characters / 8 bits

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198
Q

How many characters/bits does the Unicode character set use?

A

65,356 characters / 16 bits

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199
Q

What is sample rate measured in?

A

Frequency in Hertz

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200
Q

What is the sample rate?

A

How often the height is recorded (x-axis)

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201
Q

What is the sample resolution?

A

The accuracy to which the height is recorded (y-axis)

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202
Q

What is sample resolution “measured” in?

A

Bit depth

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203
Q

How to calculate file size of a sound file in bytes?

A

(Sample rate x Sample frequency x Length) / 8

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204
Q

What is the colour depth of an image?

A

The number of bits required to represent the number of colours in the image

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205
Q

What is the image resolution of an image?

A

The number of pixels in the image (i.e. the area of the image ~ b x h)

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206
Q

What is the image resolution of an image?

A

The number of pixels in the image (i.e. the area of the image ~ b x h)

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207
Q

What is metadata?

A

The information that allows us to recreate the image on the screen

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208
Q

How to calculate the file size of an image file in bytes?

A

(Image resolution x Colour depth) /8

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209
Q

What file formats use Lossy compression?

A

JPG, MP3, MPG

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210
Q

What are the advantages of Lossy compression?

A

Biggest reduction in file size
Least transmission time
Reduces Internet traffic and collisions

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211
Q

What are the disadvantages of Lossy compression?

A

Detail is permanently lost by reducing the colour depth, resolution or rate

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212
Q

When would Lossy compression be used?

A

Music streaming
Online images and video
Image libraries on devices or in the cloud

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213
Q

What file formats use Lossless compression?

A

TIF, PDF, GIF, PNG, ZIP

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214
Q

What are the advantages of Lossless compression?

A

Original quality is preserved / no information or data is lost

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215
Q

What are the disadvantages of Lossless compression?

A

Less significant reduction in file size

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216
Q

When would Lossless compression be used?

A

Text documents
Electronic books
High resolution documents

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217
Q

What is binary?

A

Series of 1’s and 0’s that represent values or characters
Values are stored in base-2 (denary is in base-10)
One binary digit is called a ‘bit’
8 bits make up one ‘byte’
The maximum size of the integer able to be stored depends on the number of bits used - e.g. the largest number stored by 8 bits is 255

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218
Q

Describe the use of binary in computer registers

A

A register is a location where data that the processor is using can be stored
Processors have internal registers that data can be transferred between
The register itself is a group of binary cells, where data is stored as a series of 1’s and 0’s.

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219
Q

What is binary-coded decimal and where is it used?

A

A system of writing numerals where each digit is represented by a 4-bit binary sequence
Has the advantage that there is no limit to the size of the number: to add another digit, you just need to add a new 4-bit sequence
Used in barcodes and arithmetic where every digit has to be retained in a result

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220
Q

What is hexadecimal?

A

Series of the numbers 1-9 and letters A-F that represent values or characters
Values are stored in base-16

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221
Q

Why is hexadecimal used to represent numbers?

A

Each hexadecimal digit represents 4 binary digits, so it is shorter to read
Easier for programmers to read as more characters are used (not just 1’s and 0’s)
Very large numbers can be stored in a smaller amount of space

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222
Q

List some current uses of hexadecimal numbers in computing

A

defining colours in Hypertext Markup Language (HTML)
Media Access Control (MAC) addresses
assembly languages and machine code
debugging

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223
Q

What do computers use binary to do?

A

To represent data, such as numbers, text, sound and graphics
To program instructions

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224
Q

What is 4 bits known as?

A

A nibble

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225
Q

What is 8 bits known as?

A

A byte

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226
Q

(Exam-style question)

Explain one reason why all instructions and data used by a computer are represented in binary. (3)

A

A processor consists of billions of transistors, each having just two states, on/off
The on/off states of a transistor represent the binary digits 1/0

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227
Q

(Exam-style question)

Describe a ‘bit’. (2)

A

A bit is short for binary digit, the smallest unit of data in a computer
A bit has a single binary value, either 0 or 1

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228
Q

(Exam-style question)

Give one reason why a computer doesn’t need to know what a binary pattern represents. (1)

A

The microprocessor hardware only operates on bits, so it has no concept of type or representation

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229
Q

(Exam-style question)

Write an arithmetic expression to show that 256 different colours can be represented in 8 bits. (1)

A

2⁸ = 256 colours

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230
Q

What can denary numbers also be called?

A

Decimal numbers

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231
Q

(Exam-style question)

Explain one reason why the denary number 256 cannot be represented in an 8-bit binary pattern. (2)

A

The number would be represented in binary as 100000000
You would need 9 bits to store it

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232
Q

Convert the following denary numbers into 8-bit binary numbers:

a) 203
b) 241
c) 79
d) 100

A

a) 11001011
b) 11110001
c) 01001111
d) 01100100

233
Q

Convert the 8-bit binary pattern 11011001 into a denary number.

A

217

234
Q

List two ways of representing signed integer numbers.

A

Two’s complement
Sign and magnitude

235
Q

What happens if the most significant bit of a two’s complement or sign and magnitude pattern is 1?

A

The number will have a negative value

236
Q

(Example)

Convert -10 to binary two’s complement.

A

Write out the positive number (+10) in binary: 00001010
Flip all the bits: 11110101
Add 1 (00000001) to the result. This gives: 11110110
Therefore, -10 in two’s complement is 11110110

237
Q

(Exam-style question)

Convert the denary number -54 to 8-bit binary two’s complement representation. (3)

A

11001010

238
Q

(Exam-style question)

Give the denary value of the 8-bit two’s complement number 11101111. (3)

A

-17

239
Q

(Exam-style question)

Convert the denary number -94 to a binary pattern using sign and magnitude representation. (2)

A

11011110

240
Q

(Exam-style question)

Give the result of adding 00101011 and 00010111. (2)

A

01000010

241
Q

(Exam-style question)

Add the following 8-bit binary numbers:

01010111 + 01011111

Give your answer in 8-bit binary form. (2)

A

10110110

242
Q

(Exam-style question)

Give the result of applying a logical shift left, 2 places, to the 8-bit binary pattern 00010100. (1)

A

01010000

243
Q

(Exam-style question)

Give the result of applying a logical shift right, 3 places, to the 8-bit binary pattern 10111000. (1)

A

00010111

244
Q

(Exam-style question)

Give the result of applying an arithmetic shift right, 1 place, to the 8-bit binary pattern 10001000. (1)

A

11000100

245
Q

(Exam-style question)

Give the result of applying an arithmetic shift left, 1 place, to the 8-bit binary pattern 11101100. (1)

A

11011000

246
Q

(Exam-style question)

Describe one difference between a logical and an arithmetic shift. (2)

A

An arithmetic shift preserves the most significant bit
A logical shift always fills the vacated bits with 0s

247
Q

(Exam-style question)

The binary bit pattern 10101101 is equal to the denary number 173.

Explain the effect of performing a logical shift right of two places on the binary number 10101101, and state the denary number equivalent after the shift. (3)

A

The binary number becomes 00101011 after the two-place logical right shift
The new binary number’s denary equivalent is 43
In a two-place logical right shift, the binary number is divided by 4; the result of dividing 173 by 4 is 43.25.
The right shift produces an imprecise result because it discards the two bits on the right of the binary number, effectively rounding it down to the nearest whole number

248
Q

What happens to a binary number that has been shifted right one place?

A

It has been divided by 2

249
Q

What type of binary numbers do arithmetic shifts operate on?

A

Two’s complement binary

250
Q

What type of binary numbers do logical shifts operate on?

A

Sign and magnitude binary

251
Q

(Exam-style question)

Define the term ‘overflow’. (2)

A

An error that occurs when a calculation produces a result that is greater than what the computer is able to store, or is greater than the number of bits available to store it

252
Q

(Exam-style question)

State two consequences of an overflow error. (2)

A

The program might crash
Continued use of an incorrect result in calculations will cause further errors

253
Q

(Exam-style question)

Explain one reason why the result of adding two 16-bit binary patterns together must be 16 bits in length. (2)

A

The registers inside the machine that hold the original patterns have a fixed length, so they cannot hold more than 16 bits

254
Q

(Exam-style question)

Describe one way an overflow error can be caused by shifting the 8-bit binary pattern 11000011 left by one position. (2)

A

Shifting left the original pattern 11000011 gives 10000110
The original 1 in the most significant bit is shifted out, therefore it uses a position that does not exist in the register

255
Q

(Exam-style question)

Convert the 8-bit binary number 10110111 to hexadecimal. (1)

A

B7

256
Q

(Exam-style question)

Convert the hexadecimal number E9 to 8-bit binary. (1)

A

11101001

257
Q

What are some of the uses of hexadecimal notation?

A

Used to help people deal with long binary digits as they are much shorter in hexadecimal
Error code numbers are usually given in hexadecimal when a computer malfunctions
Used to represent numerical values in assembly language

258
Q

What is the number of bits true colour uses to code every available colour variation?

A

24 bits

259
Q

Each colour is represented by three 8-bit binary numbers that can be simplified to three 2-digit hexadecimal ones.

What is the benefit of this?

A

It is much easier to remember and enter the six digits of the hexadecimal number

260
Q

(Exam-style question)

Explain why hexadecimal numbers are sometimes used to represent values stored in computers, even though computers do not use hexadecimal numbers. (2)

A

Large binary numbers can be complicated to read and work with
Binary numbers can be simplified by writing them in hexadecimal as fewer numbers are needed, making them easier to read and memorise

261
Q

What base are hexadecimal numbers in?

A

Base 16

262
Q

What do computers use ASCII and Unicode to do?

A

Encode characters

263
Q

What does ‘ASCII’ stand for?

A

American Standard Code for Information Interchange

264
Q

(Exam-style question)

Define what is meant by the ‘character set’ of a computer. (2)

A

The list of binary codes that can be recognised by a computer’s hardware and software

265
Q

(Exam-style question)

Describe how ASCII is used to represent characters in a computer system. (2)

A

ASCII is a 7-bit code, therefore making use of 128 code sequences to represent different English characters

266
Q

How many bits are used to represent characters in the ASCII character set?

A

7

267
Q

(Exam-style question)

The 7-bit ASCII code for the letter ‘Q’ is 81.

Give the ASCII code for the letter ‘H’. (1)

A

71

268
Q

(Exam-style question)

The ASCII code for the character ‘C’ is 67.

Give the ASCII code for the character ‘M’. (1)

A

77

269
Q

(Exam-style question)

Explain why Unicode was developed. (2)

A

Any from:

Uses a minimum of 16 bits, so it can represent at least 2¹⁶ characters
Before it existed, there were many different encoding systems but none could contain enough characters to represent all major languages
Standard ASCII only provides 128 different patterns, it can’t represent all major languages/symbols/characters
Unicode can represent all languages, ASCII was developed for English

270
Q

(Exam-style question)

State what is meant by the size of an image. (1)

A

The product of the no. of pixels for the image’s width (W) and the no. of pixels for its height (H)

271
Q

(Exam-style question)

State what is meant by the resolution of an image. (1)

A

The number of pixels per unit area of the display

272
Q

What is meant by colour depth?

A

The number of bits used to encode the colour of each pixel

272
Q

What is the equation to calculate the file size of an image?

A

Width × Height × Colour Depth

(file size measured in bits)

272
Q

(Exam-style question)

State what is meant by the term ‘pixel’. (1)

A

The smallest block of colour in an image

272
Q

(Exam-style question)

State what is meant by the term ‘pixel’. (1)

A

The smallest block of colour in an image

273
Q

(Exam-style question)

Describe the factors that affect the quality of a digital image. (4)

A

The quality of the image is affected by the number of pixels that make it up, therefore, the more pixels the better the image resolution
The quality of the image is affected by the number of bits used to encode the colour depth, therefore, if more bits are used, more colours can be displayed

274
Q

How is file size affected if an image has good quality?

A

The file size will be large

275
Q

What are analogue recordings?

A

Original sound recordings

276
Q

What are digital recordings?

A

Recordings that use samples of the sound at regular fixed intervals

277
Q

(Exam-style question)

Sound can be represented digitally by taking samples of the original sound.

State what is meant by sample rate. (1)

(also known as ‘sampling frequency’)

A

Sample rate describes the number of sound samples that are taken each second

278
Q

(Exam-style question)

Describe the effect of increasing the sample rate. (2)

A

Increasing the sample rate gives a more accurate reproduction of the analogue wave, as more samples are taken with less time between them

279
Q

(Exam-style question)

Explain what is meant by the bit depth of a recording. (2)

A

Bit depth describes the number of bits used to encode the data taken in each sample

280
Q

(Exam-style question)

State the effect of increasing the bit depth of a recording. (1)

A

Allows more data to be stored, meaning the range of sound can be represented more accurately

281
Q

(Exam-style question)

The sample rate and bit depth affect the size of the file produced.

Name two other factors which will affect the size of the file. (2)

A

Length of recording
Number of channels

282
Q

(Exam-style question)

An analogue signal is never fully reproducible in a digital format.

Explain one reason why this statement is true. (2)

A

A digital recording samples the analogue signal at fixed intervals
Therefore, the entire analogue signal is not represented in the digital recording

283
Q

(Exam-style question)

Describe the steps taken to convert the analogue sound to a digital sound file. (3)

A

Sample the analogue sound at equal intervals
Measure the sound amplitude
Give a binary value for each measurement
Store data as digital signals

284
Q

What is the equation to calculate the file size of an audio file?

A

Sample rate (Hz) × Bit depth × Recording length (seconds)

(file size measured in bits)

285
Q

What is 1 hertz (Hz) equal to, in terms of samples?

A

1 sample per second

286
Q

Why is the total file size for CDs doubled?

A

They are recorded in stereo and so have two channels

287
Q

State what solid line labelled A represents.

A

The digital signal

288
Q

State what the dashed line labelled B represents.

A

The analogue signal

289
Q

Give the sampling frequency, including the correct units.

A

2Hz

290
Q

Give the value in binary of the audio sample at the 4th second.

A

101

291
Q

(Exam-style question)

State the formula used to determine the number of distinct binary patterns for a known number of bits, ‘n’. (1)

A

2ⁿ

292
Q

(Exam-style question)

Describe the reason 4 bits may be the preferred way to store colour depth in an image rather than 8 bits. (2)

A

Any one from:

The increase in colours that cause a slight improvement in quality might not matter to the person viewing the image
The image may be on a web page that is transferred over the internet, which needs to load very quickly
The higher colour depth file would mean the image takes longer to transfer and loads more slowly

293
Q

(Exam-style question)

Explain one reason for reducing the bit depth of an audio recording. (2)

A

Any one from:

Reducing the bit depth reduces the file size, so the audio file will transmit faster
Reducing the bit depth reduces the number of distinct values and these may not be noticed by the human ear

294
Q

(Exam-style question)

Explain one reason that a 5-bit colour depth is needed to store 24 colours in an image. (2)

A

Five bits are needed to store 24 colours because 2⁴ = 16, which is less than 24, and 2⁵ = 32, which is the next largest power of 2 greater than 24

295
Q

(Exam-style question)

Both kibibyte and kilobyte can be used as measures of file size.

Compare kibibyte and kilobyte. (2)

A

Any one from:

Kilobyte is an SI measurement, whereas kibibyte is an International Electrotechnical Commission (IEC) measurement
Kilobyte is equivalent to 1000 bytes, whereas a kibibyte is equivalent to 1024 bytes
Kilobyte is equivalent to 10³ bytes, whereas a kibibyte is equivalent to 2¹⁰ bytes
Kilobyte is a base 10 measurement, whereas a kibibyte is a base 2 measurement

296
Q

Recall the conversions between binary multiples.

A

1 byte
= 2^0 bytes

×1024 ÷1024

1 kibibyte (KiB)
= 2^10 bytes
= 1024 bytes

×1024 ÷1024

1 mebibyte (MiB)
= 2^20 bytes
= 1024 kibibytes

×1024 ÷1024

1 gibibyte (GiB)
= 2^30 bytes
= 1024 mebibytes

×1024 ÷1024

1 tebibyte (TiB)
= 2^40 bytes
= 1024 gibibytes

297
Q

Recall the number of bytes represented by each of the following:

kilobyte, megabyte, gigabyte, terabyte

A

kilobyte (kB) - 10³
megabyte (MB) - 10⁶
gigabyte (GB) - 10⁹
terabyte (TB) - 10¹²

298
Q

Recall the number of bytes represented by each of the following:

kilobyte, megabyte, gigabyte, terabyte

A

kilobyte (kB) - 10³
megabyte (MB) - 10⁶
gigabyte (GB) - 10⁹
terabyte (TB) - 10¹²

299
Q

Recall the number of bytes represented by each of the following:

kilobyte, megabyte, gigabyte, terabyte

A

kilobyte (kB) - 10³
megabyte (MB) - 10⁶
gigabyte (GB) - 10⁹
terabyte (TB) - 10¹²

300
Q

Give some reasons for why file compression is used.

A

Less internet bandwidth is used when files are downloaded/uploaded
Transfer time is faster
Reduced file size / less storage space is needed
Smaller files reduce congestion on the internet

301
Q

Describe the purpose of lossless compression.

A

Reduces file size without deleting any data
When compressed data is uncompressed, it is restored completely to the original file

302
Q

Describe how lossless compression works.

A

Algorithms look for areas of redundancy where same data is stored many times, grouping this data into one reference

(this is an example of run-length encoding)

303
Q

Give examples of where lossless compression is used successfully and where it is used less successfully.

A

Successful uses

Text files
Graphic files with a low colour depth

Less successful uses

Audio files
24-bit colour files

304
Q

Describe the purpose of lossy compression.

A

Reduces file size by deleting some data
Changes made are irreversible and original form cannot be retrieved

305
Q

Describe how lossy compression works.

A

Image files - algorithms analyse image and find areas where there are slight differences, give these area same value and the file is rewritten with less bits
Digital sound recordings - small variations in frequency, tone and volume are removed, human ear cannot detect these small differences

306
Q

Give examples of where lossy compression is used successfully and where it is used less successfully.

A

Successful uses

Image files
Digital sound recordings

Less successful uses

Text files
Executable software

307
Q

Give 2 examples of lossy algorithms.

A

JPEG
MP3

308
Q

(Exam-style question)

Here is a string of data.
CCCWWWCCWWWWWWCCC
Give the result of compressing the string using a run-length encoding algorithm.
(1)

A

3c3w2c6w3c

309
Q

What is binary?

A

Series of 1’s and 0’s that represent values or characters
Values are stored in base-2 (denary is in base-10)
One binary digit is called a ‘bit’
8 bits make up one ‘byte’
The maximum size of the integer able to be stored depends on the number of bits used - e.g. the largest number stored by 8 bits is 255

310
Q

Describe the use of binary in computer registers

A

A register is a location where data that the processor is using can be stored
Processors have internal registers that data can be transferred between
The register itself is a group of binary cells, where data is stored as a series of 1’s and 0’s.

311
Q

What is binary-coded decimal and where is it used?

A

A system of writing numerals where each digit is represented by a 4-bit binary sequence
Has the advantage that there is no limit to the size of the number: to add another digit, you just need to add a new 4-bit sequence
Used in barcodes and arithmetic where every digit has to be retained in a result

312
Q

What is hexadecimal?

A

Series of the numbers 1-9 and letters A-F that represent values or characters
Values are stored in base-16

313
Q

Why is hexadecimal used to represent numbers?

A

Each hexadecimal digit represents 4 binary digits, so it is shorter to read
Easier for programmers to read as more characters are used (not just 1’s and 0’s)
Very large numbers can be stored in a smaller amount of space

314
Q

List some current uses of hexadecimal numbers in computing

A

defining colours in Hypertext Markup Language (HTML)
Media Access Control (MAC) addresses
assembly languages and machine code
debugging

315
Q

Binary System

A

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

316
Q

Why is binary used?

A

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

317
Q

Signed / unsigned integer

A

An unsigned integer has no positive or negative sign.
Signed: -8, +8
Unsigned: 8

318
Q

Why is the binary system used?

A

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

319
Q

Overflow

A

When the result of a binary calculation requieres more bits than are available in the computer hardware (register)

320
Q

Two’s complement, denary to binary

A

Remove the - sign
Convert the number to binary
Flip the bits
Add 1

321
Q

Two’s complement, binary to denary

A

Remove 1
Flip the bits
Convert to denary
Add a negative sign (if the original number started with a 1)

322
Q

Logical shifts

A

When doubling, shift/move all bits to the left
When halving, shift/move all bits to the right

323
Q

Bit

A

Binary digit

324
Q

Image file size formula

A

File size(bits) = width(px) x height(px) x colour depth(bits)

325
Q

Hexadecimal

A

Used to avoid errors when manipulating numbers
Represent binary numbers using smaller digits (1 hexadecimal digit = 1 nibble)
Computers don’t process hexadecimal
0-F

326
Q

Units

A

kilobit - 1000 bits
megabit - 1000^2 bits
gigabit - 1000^3 bits

kilobyte - 8 x 1000 bits
megabyte - 8 x 1000^2 bits
gigabyte - 8 x 1000^3

kibibyte - 8 x 1024 bits
mebibyte - 8 x 1024^2 bits
gibibyte - 8 x 1024^3 bits

327
Q

Compression

A

Reduce file sizes by repackging or removing some data

328
Q

Lossless compression

A

Reduce file size while retaining the exact meaning of the original data.
Works by looking for redundancy where the same data is stored many times and groups this data into one reference

329
Q

Lossy compression

A

It reduces file size by permanently deleting some of its data.

330
Q

How is text represented

A

Characters in texts

331
Q

How are characters in text represented

A

Using the ASCII table, each character has a unique bit pattern.
Is a 7-bit code, there are 128 sequences/patterns.

332
Q

How to computers record sound

A

With a microphone (or a recording device) a computer will take samples at a fixed interval (usually thousands of samples per second), it will then convert these values into binary to be stored in a file.

333
Q

Audio file size formula

A

file size (bits) = sample rate(Hz) x bit depth(bits) x recording length (seconds)

334
Q

Signed and Unsigned integer

A

An unsigned integer has no positive or negative sign, a signed one does.
Signed: -8, +8
Unsigned: 8

335
Q

What do binary digits represent?

A

They are 0 and 1 and represent the codes for instructions and data.

336
Q

How many bits in a nibble?

A

4

337
Q

How many bits in a byte?

A

8

338
Q

How many bytes in a KB?

A

1024 bytes

339
Q

How many KB in a MB?

A

1024 KB

340
Q

How many MB in a GB?

A

1024 MB

341
Q

How many GB in a TB?

A

1024 GB

342
Q

How many TB in a PB?

A

1024 TB

343
Q

What is the acronym for remembering the increasing order of file size? BITS –> PETABYTES

A

Bold - BIT
Blue - BYTE
Kites - KILOBYTE
Make - MEGABYTE
Great - GIGABYTE
Toy - TERABYTE
Planes - PETABYTE

344
Q

What does KB stand for?

A

Kilobyte

345
Q

What is the magnitude of a KB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^3 bytes or 2^10 bytes

346
Q

What does MB stand for?

A

Megabyte

347
Q

What is the magnitude of a MB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^6 bytes or 2^20 bytes

348
Q

What does GB stand for?

A

Gigabyte

349
Q

What is the magnitude of a GB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^9 bytes or 2^30 bytes

350
Q

What is the magnitude of a MB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^6 bytes

351
Q

What does TB stand for?

A

Terabyte

352
Q

What is the magnitude of a TB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^12 bytes or 2^40 bytes

353
Q

What does PB stand for?

A

Petabyte

354
Q

What is the magnitude of a PB? HINT: IN TERMS OF 10 TO THE POWER OF N

A

10^15 bytes or 2^50 bytes

355
Q

True or false: Transistors act as switches which either conduct electricity (represented by the binary digit 1) or they do not (represented by the binary digit 0). The system consists of these two states, so is called a binary system.

A

True

356
Q

What does it mean to say a number system is base 10?

A

Each place value is 10 times bigger than the place to its right.

357
Q

Which number system do we use?

A

Denary

358
Q

Which base does denary use?

A

Base 10

359
Q

What are place values?

A

A place value is the value that a digit’s position in a number gives it. For example (for decimal) in the number 356, the digit 5 has a value of 50 whereas in the number 3560, the digit 5 has a value of 500.

360
Q

What does it mean to say a number system is base 2?

A

Each place value is 2 times bigger than the place to its right.

361
Q

Which base does binary use?

A

Base 2

362
Q

Which number system does a binary system use?

A

Binary

363
Q

What is the denary equivalent of 2^0 bits in a byte?

A

1

364
Q

What is the denary equivalent of 2^1 bits in a byte?

A

2

365
Q

What is the denary equivalent of 2^2 bits in a byte?

A

4

366
Q

What is the denary equivalent of 2^3 bits in a byte?

A

8

367
Q

What is the denary equivalent of 2^4 bits in a byte?

A

16

368
Q

What is the denary equivalent of 2^5 bits in a byte?

A

32

369
Q

What is the denary equivalent of 2^6 bits in a byte?

A

64

370
Q

What is the denary equivalent of 2^7 bits in a byte?

A

128

371
Q

How many bits does one binary number have? FOR EXAMPLE: 10011010

A

8

372
Q

What does MSB stand for?

A

Most Significant Bit

373
Q

What is the MSB?

A

The bit with the largest value, farthest to the left.

374
Q

What does LSB stand for?

A

Least Significant Bit

375
Q

What is the LSB?

A

The bit with the lowest value, farthest to the right.

376
Q

What are bits?

A

BInary digiTs - they have single binary values of either 0 or 1.

377
Q

What is an integer?

A

A whole number without decimals (can be positive or negative).

378
Q

What are the three rules of binary addition?

A

0 + 1 = 1
0 + 0 = 0
1 + 1 = 0 CARRY THE 1
1 + 1 + 1 = 1 CARRY THE 1

379
Q

What is an overflow error?

A

When a calculation produces a result that is greater than the range of values that the computer can represent or store.

380
Q

What is the most famous example of an overflow error?

A

The crash of the Ariane 5 space rocket launched by the ESA (European Space Agency) in 1996.

381
Q

True or false: Binary numbers can only be added and subtracted.

A

False. Addition, subtraction, multiplication and division can be carried out on binary numbers in the same way as denary ones.

382
Q

What base does the hexadecimal system use?

A

Base 16

383
Q

What is A in hex?

A

10

384
Q

What is B in hex?

A

11

385
Q

What is C in hex?

A

12

386
Q

What is D in hex?

A

13

387
Q

What is E in hex?

A

14

388
Q

What is F in hex?

A

15

389
Q

How many digits are in the hexadecimal system?

A

16 digits - 0 to 15

390
Q

List the hexadecimal digits:

A

0 1 2 3 4 5 6 7 8 9 A B C D E F

391
Q

True or false: Computers understand hexadecimals.

A

False. Computers only understand and use the binary system.

392
Q

Why do we use hexadecimal numbers?

A

Human limitations - we get confused by large binary numbers so we simplify them by representing them in hex notation. Saves time.

393
Q

How many bits in a colour code?

A

24 bits

394
Q

How are colour codes represented?

A

Hexadecimal numbers - far easier to represent the codes as 6 hex numbers than 24 binary ones. EXAMPLE OF A COLOUR CODE: #CC3399.

395
Q

Why are # signs placed before hexadecimal numbers?

A

To let people know that the number is a hexadecimal number.

396
Q

Give 4 examples of when hexadecimals are used:

A

Error messages
Assembly language programming
Colour codes
Short-hand for binary numbers

397
Q

ASCII - What is ‘a’?

A

You can work out any lowercase letter from this by counting up to the letter (ie. z is 122) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

397
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

398
Q

ASCII - What is ‘0’?

A

You can work out any number 0-9 from this by counting up to the number (ie. 9 is 57) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

399
Q

ASCII - What is ‘ ‘? HINT: SPACE

A

Convert to binary if needed in that form.

400
Q

ASCII - What is DEL?

A

127 -> 01111111

401
Q

What is a character set?

A

The list of binary codes that can be recognised by the computer hardware and software as being usable characters.

402
Q

Why was ASCII created as the first common encoding system for text?

A

Different manufacturers used to use their own codes for their computers. However, they soon realised that if computers wanted to share information, they needed to also share a common encoding system for text.

403
Q

What does ASCII stand for?

A

American Standard Code for Information Interchange

404
Q

How many bits does ASCII use?

A

7 bits. It can represent 128 possible code sequences - these represent English characters and control actions (backspace, shift on, etc.).

405
Q

What is pseudocode?

A

A language that is similar to real programming language, but is easier for humans to understand although it doesn’t actually run on a computer. It can be easily converted to a regular programming language.

406
Q

Why was Extended ASCII created?

A

ASCII had 92 printable characters but there was always a need for more to accommodate foreign languages, mathematical symbols and special symbols for drawing pictures.

407
Q

How many bits does Extended ASCII use?

A

Extended ASCII uses the full 8 bits and was created to cater for foreign languages and graphics characters.

408
Q

How many codes are in the character set allowed by Extended ASCII?

A

256

409
Q

What can Unicode represent?

A

Unicode can represent characters in all known languages and writing systems.

410
Q

Why was Unicode introduced?

A

The Unicode Consortium introduced Unicode due to too many different versions of Extended ASCII developed by different manufacturers such as IBM and Apple.

411
Q

How many codes are in the character set allowed by ASCII?

A

128

412
Q

How many codes are in the character set allowed by Unicode?

A

Unicode uses 16 bits, allowing the use of over 65,000 characters.

413
Q

What is a pixel?

A

A pixel is the smallest possible dot on a computer screen, represented by a number of bits.

414
Q

What are images made up of?

A

A digital image is composed of many small points of colour or picture elements, pixels for short.

415
Q

How is the size of an image given?

A

The number of pixels in the width and then the number of pixels in the height. For example, 640 x 480 or 2048 x 1536.

416
Q

How does resolution affect image quality?

A

Higher resolution, better image quality.

417
Q

What is resolution?

A

The number of pixels per square inch on the computer screen. The higher the resolution, the better the picture.

418
Q

What is colour depth?

A

The number of bits used to encode the colour of each pixel.

419
Q

How many colours can be used in an image/graphic if only one bit is used to encode each pixel?

A

Only two colours can be used (2^1). The 0 represents black and the 1 represents white.

420
Q

A colour depth of three would allow how many colours to be used?

A

2^3 is 8. So 8 colours could be used.

421
Q

What is the current standard for colour depth (in bits) when representing images?

A

24-bit representation. This means that the colour data for each pixel is encoded in 24 bits with 8 bits used for each of the primary colours: red, green and blue. Each colour in the palette is a combination of these in different proportions.

422
Q

How many colour variations are allowed by 8-bit encoding?

A

Using 8-bits allows 256 different levels of each red, green and blue. Therefore 256 x 256 x 256 = 16,777,216 different colour variations are possible. This number of bits produces such a realistic image it is described as being ‘true colour’.

423
Q

In computer science, what are the primary colours?

A

Red, green and blue

424
Q

I know the number of bits. How can I find the equivalent number of bytes?

A

Divide the number of bits by 8.

425
Q

I know the number of bytes. How can I find the equivalent number of kilobytes?

A

Divide the number by 1000.

426
Q

How does colour depth and number of pixels impact file size?

A

As the number of pixels and colour depth increase, then so will the size of the image file.

427
Q

What is the equation for calculating file size of an image?

A

W x H x CD (Width x Height x Colour Depth used)

428
Q

How does image quality impact file size?

A

Better image quality, greater file size.

429
Q

Why is image quality often reduced before transmitting an image electronically?

A

To reduce the amount of time it will take to download the image after transmitting - there is always a compromise between file size and image quality. Lower image quality = faster download speeds.

430
Q

What is metadata?

A

Data about data. Included in many files, in addition to the stored data, is information about the file.

431
Q

Give 2 examples of metadata:

A

When the file was last saved
Who created the file
What the file is named
When the file was created (date/time)

432
Q

What does Exif stand for?

A

EXchangeable Image File format. The metadata stored in a digital image file contains descriptive and technical information (such as point of capture) and the data is stored in the Exif format.

433
Q

What data could be stored in Exif for image files?

A

Make and model number of the camera
Aperture setting
Speed settings
Dimensions of the image and the resultant file size

434
Q

What is sound caused by?

A

Vibrations travelling through a medium such as air, water or metal. These vibrations compress and then pull apart the air molecules thus causing changes in air pressure.

435
Q

Vibrations travel out in waves - what are these called?

A

Sound waves

436
Q

What do the sound wave vibrations cause in terms of air pressure?

A

Continuous changes to air pressure. These are shown on analogue diagrams.

437
Q

What are analogue recordings?

A

Recording methods that try to capture the continuous changes in air pressure by trying to convert all of the changes to analogous changes in voltage.

438
Q

Give 2 examples of analogue recordings?

A

vinyl albums
audio cassettes
These can capture the continuous changes in air pressure as minute changes in voltage.

439
Q

Why do computers not use analogue recordings?

A

Computers are digital. They cannot represent continuous, minute changes in voltage; each transistor is either on or off, nothing in between.

440
Q

What does analogue mean?

A

Data which can use any value in a continuous range.

441
Q

What is sampling?

A

Making a physical measurement of the amplitude of the wave at set time intervals and then converting the measurements to digital values.
Think of it as similar to making an animation - the smaller the changes between each sample and the greater number used each second, the more realistic the animation.

442
Q

What are the advantages of digital sound files? HINT: ANSWER NAMES 7

A

it can be edited and manipulated easily by computer equipment
it is more portable; it can be carried on a memory stick or SD card while a vinyl record or tape are not as portable
it can be played over and over again without deterioration. LPs and tapes deteriorate.
it can be easily copied on a computer. Expensive equipment is needed to copy a vinyl record.
digital audio files can be easily emailed, downloaded and streamed by users.
equipment to record and process digital sound is relatively cheap.
it has allowed people to produce their own commercial music at home.

443
Q

What are the advantages of digital sound files? HINT: ANSWER NAMES 7

A

it can be edited and manipulated easily by computer equipment
it is more portable; it can be carried on a memory stick or SD card while a vinyl record or tape are not as portable
it can be played over and over again without deterioration. LPs and tapes deteriorate.
it can be easily copied on a computer. Expensive equipment is needed to copy a vinyl record.
digital audio files can be easily emailed, downloaded and streamed by users.
equipment to record and process digital sound is relatively cheap.
it has allowed people to produce their own commercial music at home.

444
Q

What are the two factors that impact how accurately a digital recording will match the original sound?

A

Sample rate and bit depth

445
Q

What is sample rate?

A

The number of samples taken each second. The higher the sample rate, the more accurately the sound will be represented.

446
Q

For CDs, what is the average sample rate?

A

44,100 samples per second (44.1KHz)

447
Q

For Blu-ray audio, what is the average sample rate?

A

96,000 samples per second (96KHz)

448
Q

How many KHz is one sample when converting audio to digital form?

A

1000

449
Q

What is bit depth when converting audio to digital format?

A

The number of bits used to encode each sample.

450
Q

How does increasing bit depth impact digital audio quality?

A

Higher bit depth = more bits used to encode each sample = more accurate representing of range of sound = better audio quality

451
Q

What is the dynamic range?

A

The range of volume of sound in music.

452
Q

For CDs, what is the bit depth used for digital audio?

A

16 bits

453
Q

What is the equation for calculating digital audio file sizes?

A

sample rate x bit depth x length in seconds (x number of channels (mono or stereo) if applicable)

454
Q

What is compression?

A

Reducing the size of a file so that it takes up less storage space or bandwidth when it is transmitted.

455
Q

What are the benefits of compression? HINT: ANSWER NAMES 5

A

it uses less internet bandwidth when files are downloaded
transfer speed is quicker
takes up less storage space on the servers of storage providers
smaller files reduce congestion on the Internet, which is good for everyone
it makes audio and video files suitable for streaming

456
Q

What is lossless compression?

A

Compression where a compressed file can be decompressed to the original without any loss of data - all information will remain intact.

457
Q

What is lossy compression?

A

Compression where data is lost in the compression process and when the file is decompressed it will not contain all of the original information.

458
Q

What is a server?

A

A computer that provides files on demand to client machines.

459
Q

What is redundancy?

A

The number of items of data in a file which are repeated.

460
Q

Why are lossless compression rates of 50% relatively easy to achieve with text files?

A

They have lots of repeated items (words) and characters which are redundant and can be compressed.

461
Q

How does lossy compression reduce file size?

A

By throwing out some of the data - this is irreversible.

462
Q

Why is lossy compression unsuitable for text or program files?

A

File size is reduced by throwing out data - a book with missing letters would be unreadable, a program with missing letters/formatting would be inexecutable

463
Q

Why is lossy compression more useful for graphic and audio files?

A

Because they contain lots of information that can be discarded.

464
Q

What are RAW files?

A

Image files that have not been compressed and which contain all of the colour data are called RAW files.

465
Q

True or false: RAW in RAW files is an acronym.

A

False. RAW is not an acronym, it just means that the files is as it was when produced by a camera sensor and has not been compressed in any way.

466
Q

What exactly happens during lossy compression? HINT: WHAT DOES THE ALGORITHM DO?

A

The algorithm analyses the image and finds areas where there are only slight differences that we might not be able to distinguish. It then gives these the same value so that it can rewrite the file using fewer bits.

467
Q

What does JPEG stand for?

A

Joint Photographic Experts Group - known for ‘.jpeg’ files.

468
Q

What does WAV stand for?

A

Waveform Audio Format - known for ‘.wav’ audio files.

469
Q

What are WAV files?

A

Digital audio files that contain all of the sound data.

470
Q

How many MB would generally be in a 3 minute WAV file?

A

30 MB WAV file

471
Q

How many MB would generally be in a 3 minute MP3 file?

A

3 MB MP3 file

472
Q

How large is a WAV file compared to an MP3 file?

A

MP3 files are often about 1/10th the size of WAV files.

473
Q

What do computer networks enable? Give at least 2 examples of possible uses. HINT: ANSWER GIVES 5.

A
474
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

475
Q

What is ASCII?

A

A 7-bit character set that represents 128 different characters

476
Q

What is Unicode?

A

Unicode uses 8-32 bits per character to represent characters from languages around the world

477
Q

What is a character set?

A

A set of character codes for each key that can be represented on a keyboard

478
Q

What is a MAC address?

A

A unique identifier hat is used to identify a device on the internet. It is a 12 character hexadecimal string that is broken down into 2 parts, first part is the manufacturer ID and second part is Unique serial number of that device.

479
Q

Uses of Hexadecimal

A

Memory Dumps
HTML colours

480
Q

Give 3 characteristic of an IP address

A

Unique address
Public or Private
Static or Dynamic

481
Q

2 Types of compression

A

Lossy
Lossless

482
Q

Summary of how lossless compression works?

A

It allows the file size to be reduced without losing any of the original data. It works by searching for patterns and indexing those patterns.

483
Q

Summary of how lossy compression works?

A

Lossy compression removed data that is not needed, either because a drop in quality is acceptable or the difference can’t be detected by the human eye.

484
Q

Why is lossy compression not good for software, databases, etc.?

A

Because in lossy compression, parts of the original data are lost meaning the data can’t be put together how it was (bad for code, databases, etc.)

485
Q

Run-length encoding.

A

It groups repetitive data and stores them once.

486
Q

Dictionary encoding

A

Dictionary encoding algorithms create an index of data which require less space to store than the original data

487
Q

3 benefits of compression

A

Download speeds are increased
Real-time streaming of audio and video without buffering
Takes smaller size on disk, so you have more space to store other data

488
Q

What does compression do?

A

Reduces file size and changes various attributes of an image file. (eg. file type and resolution)

489
Q

What are the two types of compression?

A

Lossless and lossy

490
Q

What is specific about lossless compression?

A

It allows the data to be perfectly reconstructed! (eg. zip)

491
Q

What is specific about lossy compression?

A

Reduces a file permanently, eliminates certain information (especially unnecessary information) eg. JPG!

492
Q

Which compression is better for saving memory?

A

Lossy

493
Q

Which compression is better for overall quality?

A

Lossless

494
Q

why do computers use binary

A

it is the simplest method for counting available.
It is how computer code everything.
binary allows for computer to proceed millions of inputs very quickly.

495
Q

reasons for using hexadecimal?

A

-provides a shorter way to represent a byte of data.
-it uses memory, more efficiently

496
Q

what is the ASCII code?

A

it is the international agreed standard for coding a computer.
it is out link between our computer screen and computer hardware.
used to translate computer text to human text.

497
Q

examples of ASCII codes?

A

-web address
-URL

498
Q

what is sampling resolution

A

-The number of bits assigned to each sample. -Also known as bit depth.

499
Q

what is sampling rate?

A

The number of samples taken in a second.

500
Q

why does Sound need to be converted into binary?

A

For computers to be able to process it.

501
Q

sound needs to be converted into binary for computers to be able to process it. How is this done?

A

sound is captured (by a microphone), and then converted into a digital signal. And analogue to digital converter will sample a sound wave at regular time intervals.

502
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

502
Q

how do you calculate file size?

A

Pixel high x pixel wide x color depth
Divided by 8 × 1024

503
Q

how do you calculate the size of a sound file?

A

mono = sample rate x sample size x time
stereo = sample rate x sample size x time (x2)

504
Q

what is data compression?

A

Is the reduction in the number of bits needed to represent data.
Is a method in which the logical size of a file is compressed

505
Q

what are advantages of compressing data?

A

Save storage
speed up file transfer
reduce redundancy in stored data

506
Q

what is Lossy file compression?

A

bigger compression
smaller quality
When a file is compressed, data is permanently removed

507
Q

what is lossless data compression?

A

smaller compression
higher quality
When a file is compressed and restored no data is lost or removed

508
Q

What is the denary number system?

A

It is a base 10 number system, normally known as the decimal number system.

508
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

509
Q

What is the binary number system?

A

It is a base 2 number system. It is used for computing. Computers only understand binary.

510
Q

What is the hexadecimal number system?

A

It is a base 16 number system. It is used by programmers etc. Because of its ease of use as it is 4 times shorter than binary.

511
Q

How to convert from base 2 to bases 10 and 16.

A

To convert from base 2 to 10, we need to see which binary place values represent the ON state I.e: 1. Then we add all the place values of the ON state. To convert from base 2 to 16, we first divide the binary in groups of 4 each (as base 16 is 4 times base 2), after the grouping we just convert the binary to base 10 and then join all the numbers afyer converting them into base 16 based numbering.

512
Q

How to convert from base 10 to base 2 and 16?

A

To convert from base 10 to 2, we can use the successive subtraction method where we subtract the number by the biggest possible place value of base 2 until 0 is achieved, and then mark all place values used in subtraction as 1 and others as 0. Or we can use the successive division method where we are supposed to divide the number by 2 until 0 is reached and write the remainders during the process. Then flip the position of all the remainders from end to start to get the converted number. To convert from base 10 to 16, we use the same successive division method but instead divide the number by 16 and not 2.

513
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

514
Q

How to convert from base 16 to 2 and 10?

A

To convert from base 16 to 2, we write all base 16 numbers individually and then use the successive subtraction or successive division method for each number. To convert from base 16 to 10, we first write all base 16 numbers individually, then multiply them with their respectful place values, then add all the products together to get the base 10 number.

515
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

516
Q

What are some uses of the base 16 system in computers?

A

They are used in error codes, MAC Addresses, IPv6 addresses and HTML Color Codes

517
Q

What are error codes?

A

These are the memory location of the error, they allow to trace errors during program development.

518
Q

What are MAC Addresses?

A

They are numbers which uniquely identify a network device. It refers to the Network Interface Card which is a part of the device. It is usually 48bits but in some cases it is 64bit as well. It is in 6 groups of two hex digits. The first 3 groups (first half) is the identity number of the device manufacturer and the second half is the serial number of the device.

519
Q

What are Internet Protocol (IP) Addresses?

A

They are the addresses given to any device connected to a network for communication purposes. There are now two types of IP Addresses, IPv4 and IPv6. IPv4 is a 32 bit address while IPv6 is a 128 bit address. IPv4 is represented in denary form and IPv6 is represented in hexadecimal form grouped into 16bit chunks. IPv6 uses a colon as a chunk seperator instead of a decimal point.

520
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

521
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

521
Q

What are Internet Protocol (IP) Addresses?

A

They are the addresses given to any device connected to a network for communication purposes. There are now two types of IP Addresses, IPv4 and IPv6. IPv4 is a 32 bit address while IPv6 is a 128 bit address. IPv4 is represented in denary form and IPv6 is represented in hexadecimal form grouped into 16bit chunks. IPv6 uses a colon as a chunk seperator instead of a decimal point.

522
Q

What is the relation of HTML with Hex?

A

HTML is a mark up language used to represent text on a computer. In HTML text can be given colors, and, the color codes are coded in hexadecimal. Where each color spectrum has two hex values which make up 256 values each. As we have 3 basic colors, the total amount of colors available to us are 16,777,216.

523
Q

What is an overflow error?

A

An overflow error is the error which is produce when a number bigger than the bit size of the register is used resulting in overflow of the register.

524
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

525
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

526
Q

What is an overflow error?

A

An overflow error is the error which is produce when a number bigger than the bit size of the register is used resulting in overflow of the register.

527
Q

What is a logical shift?

A

A logical shift is moving the binary number to the left or right. Moving left is basically multiplying it by 2 and moving right is basically dividing it by 2.

528
Q

What is two’s complement?

A

It is a way of representation for binary numbers where the left most place value is changed to a negative value. A 1 value in the left most bit represents a negative number and a 0 represents a positive number.

529
Q

How to convert a negative number to two’s complement?

A

First we need to add the negative number into -128. E.g -97 so we will add like this: -128+97. The number we get is the left out numbers we need to put inside the rest of the binary digits to complete the number.

530
Q

What is ASCII?

A

ASCII, American Standard Code for Information Interchange is a code which is used in computers to represent letters, numbers and symbols/characters on computer and communication systems. It is 7 bit. It was set up in 1963 and a newer version was published in 1986.

531
Q

How is the binary of uppercase and lower case ASCII characters different?

A

The 6th bit I.e: second most significant bit is a 0 in uppercase and 1 in lower case.

532
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

533
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

534
Q

What is extended ASCII?

A

It is an 8 bit code which gives us additional 128 codes for use of non English alphabets and other graphical characters.

535
Q

What is the main disadvantage of ASCII?

A

ASCII can only represent characters of the western languagesASCII can only represent characters of the western languages

536
Q

What is Unicode?

A

Unicode is the solution to ASCII’s problem. It can represent all languages around the world. Unicode can support upto four bytes per character. The initial 128 characters are the same as ASCII but after that there are several thousand characters.

537
Q

What were the goals with which Unicode was published based on?

A

To create a universal standard thay covers all languages and writing systems.
To produce a more efficient coding system than ASCII
To adopt a uniform encoding where each character is encoded as 16 or 32 bit code.
To create unambiguous encoding where each 16 and 32 bit value represents the same character.
To reserve part of the code for private use so user can assign their own characters and symbols.

538
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

539
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

540
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

540
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

541
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

542
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

543
Q

ASCII - What is ‘A’?

A

You can work out any uppercase letter from this by counting up to the letter (ie. Z is 90) and then converting to binary. NO NEED TO LEARN ALL OF ASCII.

543
Q

Why computers use binary data?

A

Because computers are made up of billions of transistors (tiny switches) which are either in the ON state represented by the binary digit 1 or the OFF state represented by the binary digit 0. The base 2 number system is the perfect use for this purpose.

544
Q

What is the denary number system?

A

It is a base 10 number system, normally known as the decimal number system.

545
Q

What is the binary number system?

A

It is a base 2 number system. It is used for computing. Computers only understand binary.

546
Q

What is the hexadecimal number system?

A

It is a base 16 number system. It is used by programmers etc. Because of its ease of use as it is 4 times shorter than binary.

547
Q

How to convert from base 2 to bases 10 and 16.

A

To convert from base 2 to 10, we need to see which binary place values represent the ON state I.e: 1. Then we add all the place values of the ON state. To convert from base 2 to 16, we first divide the binary in groups of 4 each (as base 16 is 4 times base 2), after the grouping we just convert the binary to base 10 and then join all the numbers afyer converting them into base 16 based numbering.

548
Q

How to convert from base 10 to base 2 and 16?

A

To convert from base 10 to 2, we can use the successive subtraction method where we subtract the number by the biggest possible place value of base 2 until 0 is achieved, and then mark all place values used in subtraction as 1 and others as 0. Or we can use the successive division method where we are supposed to divide the number by 2 until 0 is reached and write the remainders during the process. Then flip the position of all the remainders from end to start to get the converted number. To convert from base 10 to 16, we use the same successive division method but instead divide the number by 16 and not 2.

549
Q

How to convert from base 16 to 2 and 10?

A

To convert from base 16 to 2, we write all base 16 numbers individually and then use the successive subtraction or successive division method for each number. To convert from base 16 to 10, we first write all base 16 numbers individually, then multiply them with their respectful place values, then add all the products together to get the base 10 number.

550
Q

What are some uses of the base 16 system in computers?

A

They are used in error codes, MAC Addresses, IPv6 addresses and HTML Color Codes

551
Q

What are error codes?

A

These are the memory location of the error, they allow to trace errors during program development.

552
Q

What are MAC Addresses?

A

They are numbers which uniquely identify a network device. It refers to the Network Interface Card which is a part of the device. It is usually 48bits but in some cases it is 64bit as well. It is in 6 groups of two hex digits. The first 3 groups (first half) is the identity number of the device manufacturer and the second half is the serial number of the device.

553
Q

What are Internet Protocol (IP) Addresses?

A

They are the addresses given to any device connected to a network for communication purposes. There are now two types of IP Addresses, IPv4 and IPv6. IPv4 is a 32 bit address while IPv6 is a 128 bit address. IPv4 is represented in denary form and IPv6 is represented in hexadecimal form grouped into 16bit chunks. IPv6 uses a colon as a chunk seperator instead of a decimal point.

554
Q

What is an overflow error?

A

An overflow error is the error which is produce when a number bigger than the bit size of the register is used resulting in overflow of the register.

555
Q

What is the relation of HTML with Hex?

A

HTML is a mark up language used to represent text on a computer. In HTML text can be given colors, and, the color codes are coded in hexadecimal. Where each color spectrum has two hex values which make up 256 values each. As we have 3 basic colors, the total amount of colors available to us are 16,777,216.

556
Q

What is the relation of HTML with Hex?

A

HTML is a mark up language used to represent text on a computer. In HTML text can be given colors, and, the color codes are coded in hexadecimal. Where each color spectrum has two hex values which make up 256 values each. As we have 3 basic colors, the total amount of colors available to us are 16,777,216.

557
Q

What is a logical shift?

A

A logical shift is moving the binary number to the left or right. Moving left is basically multiplying it by 2 and moving right is basically dividing it by 2.

558
Q

What is two’s complement?

A

It is a way of representation for binary numbers where the left most place value is changed to a negative value. A 1 value in the left most bit represents a negative number and a 0 represents a positive number.

559
Q

How to convert a negative number to two’s complement?

A

First we need to add the negative number into -128. E.g -97 so we will add like this: -128+97. The number we get is the left out numbers we need to put inside the rest of the binary digits to complete the number.

560
Q

What is ASCII?

A

ASCII, American Standard Code for Information Interchange is a code which is used in computers to represent letters, numbers and symbols/characters on computer and communication systems. It is 7 bit. It was set up in 1963 and a newer version was published in 1986.

561
Q

How is the binary of uppercase and lower case ASCII characters different?

A

The 6th bit I.e: second most significant bit is a 0 in uppercase and 1 in lower case.

562
Q

What is extended ASCII?

A

It is an 8 bit code which gives us additional 128 codes for use of non English alphabets and other graphical characters.

563
Q

What is the main disadvantage of ASCII?

A

ASCII can only represent characters of the western languages

564
Q

What is Unicode?

A

Unicode is the solution to ASCII’s problem. It can represent all languages around the world. Unicode can support upto four bytes per character. The initial 128 characters are the same as ASCII but after that there are several thousand characters.

565
Q

What were the goals with which Unicode was published based on?

A

To create a universal standard thay covers all languages and writing systems.
To produce a more efficient coding system than ASCII
To adopt a uniform encoding where each character is encoded as 16 or 32 bit code.
To create unambiguous encoding where each 16 and 32 bit value represents the same character.
To reserve part of the code for private use so user can assign their own characters and symbols.

566
Q

Why is binary used?

A

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

567
Q

Overflow

A

When the result of a binary calculation requieres more bits than are available in the computer hardware (register)

568
Q

Two’s complement, denary to binary

A

Remove the - sign
Convert the number to binary
Flip the bits
Add 1

569
Q

Two’s complement, binary to denary

A

Remove 1
Flip the bits
Convert to denary
Add a negative sign (if the original number started with a 1)

Computer Science Flashcards (6 decks)

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