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Computer Science GCSE > Paper 2 > Flashcards

Paper 2 Flashcards

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1
Q

Ascii

A
  • American Standard Code for Information Interchange
  • A character encoding standard
  • 7 bits per character - room for 128 characters (2^7)
  • Can only represent English
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2
Q

Unicode

A
  • Can represent thousands of characters
  • 16 bits per character
  • Developed as a response to the limitations of ASCII
  • Allows characters from all major lanuages to be represented
  • Uses a lot more storage
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3
Q

What is image size?

A
  • width x height
  • Image size is the total amount of pixels that make up a bitmap image
  • Higher the image size, the higher the quality
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4
Q

What is colour depth

A
  • Number of bits per pixel
  • The higher the colour depth, the more detailed the image is
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5
Q

How to calculate bitmap file size

A
  • Image size x colour depth
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6
Q

How is sound digitalized

A
  • Sound is normally produced analogue (can’t be used in a computer)
  • We digitalize sound by taking samples
  • Take samples of the amplitude at regular time intervals
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7
Q

What is the sampling rate

A
  • The number of samples taken per second
  • Measured in Hz
  • The higher the sample rate, the closer to the original sound wave the digital version looks
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8
Q

What is the sample resolution

A
  • Number of bits per sample
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9
Q

How to calculate file size (sound)

A
  • Rate x resolution x seconds
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10
Q

What is the aim of compression

A
  • To reduce file size
  • Shorter transmission times, more data stored on a device
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11
Q

What is LOSSY data compression

A
  • Loses some parts of the file permanantly (irreversible)
  • Used for sound and images and some quality can be lost
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12
Q

What is LOSSLESS data compression

A
  • Just rearranges the file to be stored in a more efficient way or encodes it in a different format
  • Used for documents
  • Reversible compression
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13
Q

How is Huffman coding done

A
  • Gives the most frequent characters the shortest code
  • Start from the top of the tree
  • Binary - 1 on right, 0 on left
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14
Q

Run Length Encoding (RLE)

A
  • Stores data in frequancy-value pairs
  • EG: AAABBBCC = 3A3B2C
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15
Q

High level code

A
  • Like written in English
  • More readable
  • Portable - can run on many CPUs
  • Much slower
  • Allow easy debugging
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16
Q

Low level code

A
  • Easier to optimise
  • Specific to CPUs - every CPU has its own low level code
  • Machine code and assembely code (machine is binary, assembely is a step above)
  • Allows direct control over the hardware
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17
Q

What does an assembler do

A
  • Assembley code to machine code
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18
Q

What does a compiler do

A
  • High level to machine code
  • Translate all of the code
  • No source code needed to run
  • Will not stop if errors - bad for debugging
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19
Q

What does an interpreter do

A
  • High level to machine code
  • Translates one line at a time
  • Source code needed to run
  • Will stop if error - good for debugging
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20
Q

Components of the CPU

A
  • ALU - carries out maths and logic calculations
  • Control Unit - coordinates the F-E cycle and decodes instructions
  • Cache - small, fast memory that briefly holds data the CPU will need
  • Clock - produces a regular signal to synchronize items
  • Bus - wires that connect components
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21
Q

Von Neumann Architecture

A
  • Design that uses all of the CPUs components
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22
Q

Fetch - Exectue cycle

A
  • Fetch: next instruction is fetched from the RAM into the CPU
  • Decode: CPU works out what needs to be done
  • Execute: instruction is carried out, any additional data is fetched
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23
Q

RAM vs ROM

A
  • RAM is volatile, ROM is non-volatile
  • RAM holds open programs and data, ROM contains the program that the computer needs to boot
  • We can’t change ROM
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24
Q

Wired vs wireless network

A
  • Wired: less prone to interferance, greater reliability and bandwidth, fixed range
  • Wireless: fewer wires, flexible, easy to add more devices
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25
Q

Star vs bus topology

A
  • Star: reliant on the central node, easy to add new devices
  • Bus: simple and cheap to set up, low performing (many collisions)
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26
Q

Types of cyber threats

A
  • Pharming - redirecting a user to a fake website
  • Social engineering - tricking humans
  • Phishing - getting information via fake messages
  • Blagging - inventing fake scenarios
  • Shouldering - observing people enter passwords
  • Malwares - malicious software
  • Virus - replicates when host runs
  • Trojan - hides inside useful software
  • Outdated software - weaknesses can be exploited
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27
Q

Detection and prevention of cyber threats

A
  • Penetration testing: white box (internal attack - has knowledge) and black box (external attack - has no knowledge)
  • Firewalls - check packets of data and block them if they don’t meet rules
  • Mac address filtering - access can be granted and denied based on the device
  • Biometrics and captcha - checking it is the right human
  • Automatic software updates to keep software up to date
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28
Q

Data table key terms

A
  • Record = row
  • Field = column
  • Primary key = uniquely identifies a record
  • Foreign key = primary key from another table
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29
Q

SQL select query

A

SELECT Field
FROM Table
WHERE Condition
ORDER BY Field ASC/DESC

WHERE table.primaryKey = table.foreignKey

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30
Q

Why do computers use binary?

A
  • CPUs consist of billions of little transistors. Transistors can only be in a state of on or off
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31
Q

Hexadecimal

A
  • Base-16 number system
  • Made up of 16 digits
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32
Q

What is a nibble?

A
  • A group of 4 digits
  • 1 hexadecimal digit can represent up to 4 digits (1 nibble)
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33
Q

Why do we use hexadecimal?

A
  • Easier to read than binary with big numbers
  • Uses less digits to store bigger numbers than binary
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34
Q

What is a bit pattern?

A
  • A collection of binary numbers
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35
Q

Bit vs byte vs nibble vs megabyte

A
  • 1 byte = 8 bits
  • 1 nibble = 4 bits
  • 1 megabyte = 1000 bytes
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36
Q

Left shift vs right shift

A
  • Left shift multiplies by 2
  • Right shift divides by 2
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37
Q

What is a bitmap?

A
  • An image made up of lots of small squares, called pixels
  • A pixel is a singular point in an image and is stored as binary code
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38
Q

How does image size and colour depth effect file size?

A
  • The higher the image size, the greater the number of pixels in the iage and therefore, the greater the number of bits required to store
  • The greater the colour depth, the greater the number of bits stored per pixel
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39
Q

How to calculate number of colours from colour depth?

A
  • Number of colours = 2 ^ colour depth
40
Q

What is Huffman coding?

A
  • A method of lossless compression used on text based documents
41
Q

What is hardware?

A
  • The pysical components of a computer system that you can touch
42
Q

What is software?

A
  • The programs that controls the hardware, live on the computer system
43
Q

What is system software?

A
  • Software that controls the hardware and allows other applications to run on it
  • E.G: operating system
44
Q

What is application software?

A
  • Software added to the system that allows the user to carry out a specific task
  • E.G: web browser
45
Q

What is an operating system?

A
  • A software that provides an interface between the user and the hardware of the computer system
46
Q

What is user interface with examples?

A
  • A user interface is how the user interacts with the operating system
  • E.G: Graphical User Interface (GUI)
47
Q

Memory and process management

A

Memory management:
- The process by which the OS allocates RAM to different programs that are open at the same time
- Makes multitasking possible
Process managament:
- Allocating each program enough time form the processor to run

48
Q

What are the main roles of an operating system?

A
  • Provide a user interface
  • Memory & processor management
  • I/O management & device drivers
  • Application & security management
  • File management
49
Q

I/O management and device drivers

A

I/O management:
- Manages the way that Input and Output devices interact with the system
- The OS allocates resources to I/O devices to ensure efficient operation
Device drivers:
- A piece of software used to control a piece of hardware
- I/O devices require device drivers to be used by the operating system
- Are OS specific

50
Q

Application and security management

A

Application management:
- Process carried out by the OS that allows apps to talk directly to hardware and software through the use of APIs
Security management:
- Process carried out by the OS allowing different users to log onto a computer
- Able to allocate different system rights to different users

51
Q

File management

A
  • The OS manages where and how data is stored in both primary and secondary storage
52
Q

What is utility software with examples?

A
  • Software that is designed to help maintain, enhance and repair a computer system
  • E.G: Task manager
53
Q

What is defragmentation?

A
  • Done by utility software
  • Software groups fragmented files back together in order to improve access speed
  • As files get deleted, gaps are left in a disl
  • These gaps get filled by new data and data becomes fragmented
  • Defragmentation can only be used on magnetic storage
54
Q

What is encryption?

A
  • The process of scrambling data using an algorithm so it can only be read using a key
55
Q

How does clock speed effect the performance of the CPU?

A
  • The faster the clock speed, the more instructions can be fetched and executed per second
56
Q

How does cache size effect the performance of the CPU?

A
  • The larger the cache size, the more frequently used instructions or data can be stored
  • This means that the CPU has fewer fetch cycles so the performance will speed up
57
Q

How does processor cores effect the performance of the CPU?

A
  • Multiple core processors mean they have multiple separate processing units that can fetch, decode and execute instructions at the same time - higher performance
58
Q

What is an embedded system?

A
  • A computer system with a dedicated function embedded in a much larger mechanical unit
  • E.G: traffic lights
59
Q

Different types of memory and their characteristics

A
  • RAM: stores program and data currently in use
  • ROM: stores start-up instructions of the computer
  • Cache: stores copies of frequently used instructions for efficiency
  • Register: stores instructions / data the computer is working on
60
Q

Why do we need main memory?

A
  • Access times are shorter than secondary storage
  • Time for fetch-execute cycle is reduced
61
Q

Why do we need secondary storage?

A
  • Long term storage of data that is not currently in use
  • Much larger capacity and easily portable
62
Q

What is magnetic storage and its pros and cons?

A
  • Non-volatile secondary storage that uses magnets to story binary values
  • Pros: large capacity, low cost, moderate speeds
  • Cons: can easily be damaged, very loud, bulky and hard to transport
63
Q

What is solid state storage and its pros and cons?

A
  • Non-volatile secondary storage that uses electronic circuits to store binary values
  • Pros: very fast speed, very durable (no moving parts), silent
  • Cons: low capactiy, very high cost, limited read-write cycles
64
Q

What is optical storage and its pros and cons?

A
  • Non-volatile secondary storage that uses lasers to burn the surface of a disk, creating pits and land which can be used to store 0s and 1s
  • Pros: low cost, silent, durable (no moving parts)
  • Cons: very low capacity, very slow speeds, unreliable (prone to scratches)
65
Q

What is cloud storage and its pros and cons?

A
  • Long term secondary storage of data that resides in a remote location and can be accessed via a wide area network (WAN)
  • Pros: reliable, unlimited capacity, allows for collaboration
  • Cons: high costs, must have a storng internet connection
66
Q

What is a flat file database?

A
  • One that stores all data in a single table
  • Simple and easy to understand but causes data reduncacy, inefficient storage and is harder to maintain
67
Q

What is a relational database?

A
  • One that organises data in multiple tables
  • It uses keys to connect related data which reduces data redunancy, makes efficient use of storage and is easier to maintain
68
Q

What is a table, record and field?

A
  • Table = complete set of records about the same topic in a database
  • Record = a complete set of fields on a single identity (a row)
  • Field = a single piece of data in a table (column)
69
Q

What is a primary and foreign key?

A
  • Primary key = a unique field that can be used to identify a record in a table
  • Foreign key = a field in a table that refers to the primary key in another table. Used to link two tables together
70
Q

SQL data insert

A

INSERT INTO table(fields)
VALUES(“value”)

71
Q

SQL data update

A

UPDATE table
SET field = “value”
WHERE condition

72
Q

SQL data delete

A

DELETE FROM table
WHERE condition

73
Q

What is a privacy issue and some examples?

A
  • An issue that comes from collecting, accessing or using personal information without consent or control
  • E.G: face recognition, GPS
74
Q

Examples of ethical issues

A
  • Digital divide: increasing reliance on computers increases the digital divide, creating an inequality between those with who have access to technology and those who don’t - can hinder oppurtunities for education
  • Intellecutal property: the ease of digital copying and distribution raises ethical questions about protecting personal data
75
Q

Examples of environmental issues

A
  • Natural resources: a great number of natural resources are used in the manufacturing of electrical components
  • Energy consumption: an increase in demand for 24/7 access to the internet has increased the enrgy required to maintain it
  • Throw-away society: as consumption of technology increases, so does the rapid disposal of devices. Larger volume of waste in landfill
76
Q

What is the Data Protection Act (2018)?

A
  • A law that protects personal data from being misused
  • Personal data must be: fairly processed, correctly collected, not excessive, kept up to date, not kept longer than needed
77
Q

What is the Computer Misuse act (1990)?

A
  • Law concerning the malicious use of computers
  • Unauthorised access to computer materials
  • Unauthorised access with intent to commit further offences
  • Unauthorised modification of computer files
78
Q

What is the Copyright and Patents act (1988)?

A
  • Protects the intellectual property of an individual
79
Q

What is software license?

A
  • A legal agreement that lays out the rules for how software can and can’t be used
80
Q

Pros and cons of a network?

A

Pros:
- Users can share resources
- Users can access their files from any computer
- Users can share files and data easily
Cons:
- Increased security risk to data
- Malicious content can infiltrate network and effect all connected devices
- Performance of the network can be impacted

81
Q

What is a network?

A
  • Two or more computers joined together with the purpose of sharing resources
82
Q

What are the different types of network?

A
  • LAN (Local Area Network) = network with a small geographical area owned by the company or organisation that is using it
  • WAN (Wide Area Network) = network with a large geographical area which is a collection of LANs joined together - owned by multiple different organisations
  • PAN (Personal Area Network) = very short range and used for data transmission between devices at a close proximity - BLUETOOTH
83
Q

What are the characteristics of ethernet wires?

A
  • Carries electrical signals between devices on a LAN
  • Common in homes and offices
  • Uses twisted pair cables
84
Q

What are the characteristics of fibre optic cables?

A
  • Uses light to transmit data on a WAN
  • Transmits data at much higher speeds and bandwiths
  • Does not suffer from interferance
  • Can cover long distances with any degredation
85
Q

What are the characteristics of copper cables?

A
  • Used to transmit voice signals (landline phone)
  • Degrade over time and have limited range
  • Suffer from interferance
  • Transmits data at a slower rate and lower bandwith
86
Q

What is a topology?

A
  • All devices connected in a network are reffered to as a node
  • A network topology is the arrangement in which all nodes are connected together
87
Q

Star topology pros and cons

A
  • Pros: if any single cable stops working, the rest of the network will continue to work
  • Cons: the central switch is a single point of failure
88
Q

Bus topology pros and cons

A
  • Pros: easy and cheap to set up, does not rely on any other network hardware
  • Cons: low security as data is seen by all devices, slow data transfer due to collisions, if the cable breaks, everything breaks
89
Q

Why and how do we protect a network?

A
  • To protect sensitive information and data
  • Authentication = using credentials to check if a user is who they say there are
  • Encryption = method of converting plain text into deciphered text
  • Firewall = creates a barrier between a network and the internet
  • MAC address filtering = determines if a device can or cannot be connected to a network
90
Q

What is a layer (networks)?

A
  • A layer is a sub part of a more complex task
  • Dividing network tasks into layers reduces the complexity and makes each layer more manageable
91
Q

What is the TCP/IP model?

A
  • Made up of 2 protocols which contains 4 layers
  • Application layer = software such as web browswer. Protocols: HTTPS, FTP, SMTP, IMAP
  • Transport layer = enable communication between two hosts to set up settings such as size of packets. Protocols: TCP, UDP
  • Internet layer = addresses and packages data for transmission, routes the packets across the network. Protocols: IP
  • Link layer: physical network hardware is located
92
Q

What is TCP/IP protocols?

A
  • Transmission control protocol (TCP) and internet protocol (IP) that combined allow communication over the internet (WAN)
  • TCP is responsible for making sure communication between two routers is error free
  • IP is responsible for making sure data is delivered to the right device on a wide area network (WAN)
93
Q

What is HTTP/HTTPS protocols?

A
  • Allows communication between servers and clients for web viewing
  • Allows clients to send and receive data from a server
  • HTTPS is encrypted
94
Q

What is FTP protocol?

A
  • File Transfer Protocol
  • Allows sending and receiving files between computers
  • Allows dowloading files fform the internet
95
Q

What is IMAP and SMTP protocol?

A
  • SMTP = allows communication between an email sender and the email server
  • IMAP = allows communication between the email server and the recipient

Computer Science GCSE (2 decks)

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