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GCSE Revision Flashcards > Computer Science: Key Knowledge > Flashcards

Computer Science: Key Knowledge Flashcards

1
Q

What is volatile memory?

A

Memory which will lose all the data when the power is turned off

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2
Q

Is RAM volatile or non-volatile?

A

Volatile

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3
Q

What is fast access storage?

A

Storage which is quicker to access by the CPU

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4
Q

What does RAM hold?

A

Parts of the operating system currently in use when the PC is in use

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5
Q

What are the 5 data types?

A

Integer, real/float, char, string, Boolean

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6
Q

How large is RAM?

A

A few GB in size

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7
Q

Are CPU registers and CPU cache volatile or non-volatile?

A

Volatile

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8
Q

What is an integer?

A

A while number such a 156, 0 or -54

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9
Q

How much space does an integer type take up?

A

2 bytes

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10
Q

What is a float or real number?

A

Number with a fractional part such as 1.5276, -68.4 or 20.0

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11
Q

How much space does a float or real number take up?

A

4 bytes

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12
Q

What is a char date type?

A

A single ASCII character such as A, b, 3, ! or space

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13
Q

How much space does a char data type take up?

A

1 byte

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14
Q

What is a string?

A

Data containing zero or more characters

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15
Q

How much space does a string take up?

A

1 byte per checker in the string

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16
Q

What is a Boolean?

A

Can only take the values true/false

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17
Q

How much space does a Boolean take up?

A

Theoretically just 1 bit, but in high level languages, more like a byte

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18
Q

What is virtual memory?

A

Volatile memory created temporarily on the storage drive

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19
Q

When is virtual memory required?

A

When the computer is running too many processes/RAM is being slow

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20
Q

How does virtual memory affect the computers speed?

A

It slows the computer down - copying to hard disk takes much longer than reading/writing RAM

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21
Q

What is a syntax error?

A

The rules for writing python have been broken

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22
Q

What is a logic error?

A

The code runs but gives an incorrect answer

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23
Q

What is concatenation?

A

Joining together. The ‘+’ concatenate operator is used to join together strings

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24
Q

Is ROM volatile or non-volatile memory?

A

Non-volatile

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25
Q

What is non-volatile memory?

A

When the data is stored even when the power is turned off

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26
Q

What is ROM used for?

A

Launching a PC’s operating system from the BIOS. Also used in embedded systems as a small store of software

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27
Q

What is the CPU?

A

The computer’s brain.

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28
Q

What is the purpose of the CPU?

A

Carry out the fetch-decode-execute

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29
Q

What is the fetch-decode-execute cycle?

A

CPU fetches next instruction from RAM, works out what to do and then carries out the instruction

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30
Q

What is the purpose of the Control Unit (CU)?

A

Controls the flow of data inside the CPU (to registers) and outside the CPU. to RAM and input/output devices

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31
Q

Is the hard disk volatile or non-volatile?

A

Non-volatile

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32
Q

How does sample rate frequency affect accuracy and sound file size?

A

The greater the sample frequency, the greater the accuracy and file size

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33
Q

What is the equation for calculating sound file size?

A

Sound file size = sample rate x bit depth x duration

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34
Q

How far do hex conversions go up to?

A

15

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35
Q

What is the largest hex number?

A

F

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36
Q

What is the largest binary number?

A

1111

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37
Q

What sound range can humans hear?

A

20 - 20,000 Hz

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38
Q

What are analogue signals?

A

Continuous

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39
Q

What are digital signals?

A

Discrete

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40
Q

How is sound digitized?

A

By repeatedly measuring and recording the sound wave

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41
Q

What does ADC stand for?

A

Analogue to digital conversions (inputs to digital signals)

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42
Q

What does DAC stand for?

A

Digital to audio converter (digital signals to outputs)

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43
Q

What is a sound sample?

A

A measurement of the amplitude of a sound wave at a given time

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44
Q

What determines how closely a wave is sampled on the y-axis?

A

Bit depth

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45
Q

What is the sample rate?

A

Samples per second (measured in Hz)

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46
Q

What is sample resolution?

A

The number of bits used to record each measurement

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47
Q

What does 1Hz mean?

A

1 sample per second

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48
Q

What is metadata?

A

Data about data

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49
Q

Give 2 examples of metadata:

A

Any 2 from:
file size, author, name, date last opened, etc.

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50
Q

What does DPI stand for?

A

Dots Per Inch

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51
Q

How does DPI affect image quality?

A

Higher DPI, better image quality

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52
Q

What are images made up of?

A

Pixels

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53
Q

What does each pixel represent?

A

A colour that is given a unique binary code

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54
Q

What is resolution?

A

The number of pixels in an image.

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55
Q

How does resolution effect image quality?

A

Higher resolution, better image quality

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56
Q

How does resolution affect file size?

A

Higher resolution, higher file size

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57
Q

What is increased colour depth?

A

Where more bits are stored per pixel - better quality, larger file size

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58
Q

Explain how to calculate the file size of a bitmap:

A
  1. Find the number of pixels. Example - 16 x 16 = 256
  2. Count the colours. Check powers. Example - 7 colours. 2^3 = 8 (2^2 is not enough)
  3. So we need 3 bits per pixel
  4. Size of an image = no. of pixels x bit depth -> 768 bits
  5. If necessary, divide by 8 to convert to bytes
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59
Q

What is any number to the power of 1 equal to?

A

0

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60
Q

Why do we use binary?

A

Because the CPU is made up of millions of transistors. These can either be on/off - 0/1.

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61
Q

What is MOD?

A

The remainder after dividing.

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62
Q

What is 5 MOD 2?

63
Q

What are denary numbers?

A

Normal numbers - base 10

64
Q

What is lossless compression?

A

Compression where no data is lost

65
Q

What is lossless compression?

A

Compression where some data is lost (not really a visible difference, but decreased quality)

66
Q

How does image quality affect file size?

A

Higher file size, better image quality. Lower file size, lower quality.

67
Q

What is capacity?

A

How much something can store

68
Q

What is portability?

A

How portable something is

69
Q

What is durability?

A

How durable something is

70
Q

What is speed (of data transfer)?

A

How fast data is transferrd

71
Q

What is reliability?

A

How reliable something is, how long it will last

72
Q

What is price?

A

How much something costs

73
Q

Give 2 examples of input devices:

A

Any 2 from:
Mouse, keyboard, joystick, barcode scanner, microphone

74
Q

Give 2 examples of output devices:

A

Any 2 from:
Headphones, speakers

75
Q

What is the equation for calculating text file size?

A

Text file size = Bits per character x Number of characters

76
Q

What are the 3 types of secondary storage?

A

Optical, magnetic, solid state

77
Q

Name 2 examples of solid state storage:

A

Any 2 from:
USB flash drive, SSD hard drive, SD card

78
Q

Name 2 examples of optical storage:

A

Any 2 from:
Blu-ray, DVD RAM, CD ROM

79
Q

Name 2 examples of magnetic storage:

A

Any 2 from:
Hard disk drive, Floppy disk drive, Backup tape drive

80
Q

What does magnetic storage consist of?

A

This consists of tiny magnetic particles responsible for storing your data

81
Q

What does optical storage consist of?

A

This consists of a laser beam which burns dark pits onto the surface of a disk. The pits are read in binary - a pit represents a ‘1’, no pit represents a ‘0’

82
Q

What does solid state storage consist of?

A

This consists of a series of electronic switches which hold data temporarily. Open switches represent a ‘1’. Closed switches represent a ‘0’. These are read in binary.

83
Q

What does != mean?

A

Not equal to

84
Q

What does > mean?

A

Greater than

85
Q

What does < mean?

86
Q

What does >= mean?

A

Greater than or equal to

87
Q

What does <= mean?

A

Less than or equal to

88
Q

What does == mean?

89
Q

What does the hat ‘^’ symbol mean?

A

To the power of

90
Q

What does the ‘*’ symbol mean?

91
Q

What does the ‘/’ symbol mean?

92
Q

What does ASCII use to represent characters?

93
Q

How many values does ASCII represent?

A

128 (0-127)

94
Q

What is Null in ASCII?

95
Q

What is A in ASCII?

96
Q

What is DEL in ASCII?

97
Q

What is the equation for sound file size?

A

File size (bits) = sample rate x bit depth x duration

98
Q

Give one advantage and one disadvantage of optical secondary storage:

A

Advantage: Relatively low cost
Disadvantage: Low durability - risk of scratching disk

99
Q

Give one advantage and one disadvantage of solid state secondary storage:

A

Advantage: Very portable
Disadvantage: Expensive

100
Q

Give one advantage and one disadvantage of magnetic secondary storage:

A

Advantage: Largest capacity
Disadvantage: Low durability - moving parts

101
Q

Name the different types of sorts:

A

Binary search, bubble sort, merge sort, linear search, insertion sort

102
Q

Give 2 examples of issues:

A

Any 2 from:
Ethical, cultural, environmental, technological, industrial

103
Q

What is selection?

A

An if statement. Something which runs depending on a specific condition

104
Q

What is iteration?

A

A loop. A piece of code that is repeated.

105
Q

What are the 8 conditions laid out in the Data Protection Act? (JUST READ IF NECESSARY)

A
  1. Confidential information that is no longer required should be properly disposed of
  2. Data must be obtained fairly - not transferred company to company
  3. Data collected for one purpose (ie. CCTV) cannot be used for another purpose (ie. spying on staff)
  4. Do not disclose/reveal data without a person’s consent
  5. Data must be relevant and not excessive
  6. Data must be accurate and up to date
  7. Retain data for no longer than necessary
  8. Provide a copy of the data upon request
106
Q

What are the 4 offences listed in the Computer Misuse Act?

A
  1. Unauthorised access to computer material
  2. Unauthorised access with intent to commit or facilitate a crime
  3. Unauthorised modification of software or data
  4. Making, supplying or obtaining anything which can be used in computer misuse offences
107
Q

What are inventions covered by?

108
Q

What do patents do?

A

Prevent anyone using an idea for 20 years

109
Q

What are books, music and software covered by?

110
Q

How long does copyright last?

A

70 years after publication or the author’s death

111
Q

What is the purpose of copyright?

A

To allow the author to decide how their work can be used

112
Q

What is open source software?

A

Software where the source code is made available. Users may legally modify the source code and share it under the same licence

113
Q

What is proprietary software?

A

Software where only the compiled code is released and usually this costs money. The licence prevents users from modifying or editing the software. Examples include word and excel.

114
Q

What does APPEARS stand for?

A

A - Accurate
P - Purpose
P - Processing
E - Excessive
A - Accountable
R - Retention
S - Security

115
Q

How many values are in Extended ASCII?

116
Q

How many bits does Extended ASCII use?

117
Q

How many bits does ASCII use?

118
Q

How many values are in Unicode?

119
Q

How manty bits does Unicode use?

120
Q

What does ASCII stand for?

A

American Standard Code for Information Interchange

121
Q

How manty bits does Unicode use?

122
Q

How does lossless compression work?

A

Algorithm finds groups of repeating data and records the data once along with the number of repetitions

123
Q

Give 2 examples of network security threats:

A

Any 2 from:
Poor network policies, malware, phishing, SQL injection, DoS attack, data interception, brute force attacks, social engineering

124
Q

What is social engineering?

A

A technique used by criminals to trick/manipulate people into revealing confidential information - info is gained to gain computer access

125
Q

Give 2 examples of social engineering:

A

Any 2 from:
Fake emails which require info/downloads, USB in a public zone, phishing

126
Q

What is phishing?

A

Sending emails from trusted organisations (ie. tax, bank) to trick someone into providing account information

127
Q

What is a brute force attack?

A

Where software is used to try every possible combination of words, numbers and symbols to crack a password

128
Q

How could you prevent a brute force attack?

A

Limit number of password attempts, use captchas (swirly letters computers can’t read)

129
Q

What is a Denial of Service attack?

A

A criminal uses software to bombard a web server with fake requests from one computer/internet connection. This uses up server memory and CPU cycles in order to crash the server - more often for revenge than obtaining data

130
Q

What is a Distributed Denial of Service attack?

A

A DoS attack which uses many computers infected with botnet malware to spam servers with simultaneous requests

131
Q

What is data interception?

A

Where someone gets in between you and what you’re doing online - if connected to a risky network, they may spy on your screen and even edit messages sent from your device

132
Q

Give 2 ways in which data interception could be prevented:

A

Any 2 from:
VPN, up to date anti-viral software, being alert to phishing scams, spotting the signs of a ‘man in the middle’ - long sudden page delays, HTTPS to HTTP in the URLs

133
Q

What does VPN stand for?

A

Virtual Private Network

134
Q

What are the 4 types of harmful software?

A

Malware, Spyware, Ransomware, Trojans (as in trojan horse)

135
Q

What is SQL Injection?

A

When an attacker enters malicious code into a web forum. If there are any vulnerabilities, the injection can bypass the authentication process allowing access to the backend database

136
Q

Give 2 ways to prevent SQL injection:

A

Any 2 from:
Updating and patching software regularly, using a firewall to filter data, using data validation to check input data (ie. email format ‘@’)

137
Q

What are network policies?

A

Formal documents containing the rules that you must follow in order to use a network

138
Q

What is an embedded system?

A

A computer system that is made up of both hardware and software - often known as firmware

139
Q

Give 2 examples of embedded systems:

A

Any 2 from:
MRI scanner, watch, traffic lights, microwave, dishwasher

140
Q

What does CPU stand for?

A

Central Processing Unit

141
Q

Order the levels of cache by speed (1 being fastest):

A

Level 1, Level 2, Level 3

142
Q

What is the function of the Control Unit (CU)?

A

Decodes instructions and controls the timing of operations in the CPU

143
Q

What is the function of the Arithmetic Logic Unit (ALU)?

A

Performs arithmetic and logic calculations

144
Q

What is the function of the Program Counter (PC)?

A

Calls the next instruction

145
Q

What is the function of the Memory Address Register (MAR)?

A

For the memory location of data to be fetched

146
Q

What is the function of the Memory Data Register (MDR)?

A

Data recieved from the RAM

147
Q

What is the function of the Accumulator (ACC)?

A

Stores the results from the ALU

148
Q

What is clock speed?

A

Cycles per second, measured in Hz (Hertz)

149
Q

How does clock speed affect CPU performance?

A

Faster the clock speed, faster the CPU can process instructions

150
Q

What are processor cores?

A

The number of processor cores in one CPU. A dual-core processor has 2 processes in 1 integrated circuit, in order to perform 2 tasks at once

151
Q

How will having more processor cores affect CPU performance?

A

More processor cores, faster CPU performance

152
Q

What is cache?

A

Memory on the CPU that is faster than RAM but slower than registers

153
Q

What are the rules when adding binary?

A

0 + 0 = 0
1 + 0 = 0
1 + 1 = 0 carry the 1
1 + 1 + 1 = 1 carry the 1

GCSE Revision Flashcards (21 decks)

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