Paper 2 Flashcards
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
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
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
4
Q
What is colour depth
A
- Number of bits per pixel
- The higher the colour depth, the more detailed the image is
5
Q
How to calculate bitmap file size
A
- Image size x colour depth
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
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
8
Q
What is the sample resolution
A
- Number of bits per sample
9
Q
How to calculate file size (sound)
A
- Rate x resolution x seconds
10
Q
What is the aim of compression
A
- To reduce file size
- Shorter transmission times, more data stored on a device
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
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
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
14
Q
Run Length Encoding (RLE)
A
- Stores data in frequancy-value pairs
- EG: AAABBBCC = 3A3B2C
15
Q
High level code
A
- Like written in English
- More readable
- Portable - can run on many CPUs
- Much slower
- Allow easy debugging
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
17
Q
What does an assembler do
A
- Assembley code to machine code
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
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
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
21
Q
Von Neumann Architecture
A
- Design that uses all of the CPUs components
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
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
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
25
Star vs bus topology
- Star: reliant on the central node, easy to add new devices
- Bus: simple and cheap to set up, low performing (many collisions)
26
Types of cyber threats
- 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
27
Detection and prevention of cyber threats
- 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
28
Data table key terms
- Record = row
- Field = column
- Primary key = uniquely identifies a record
- Foreign key = primary key from another table
29
SQL select query
SELECT Field
FROM Table
WHERE Condition
ORDER BY Field ASC/DESC
WHERE table.primaryKey = table.foreignKey
30
Why do computers use binary?
- CPUs consist of billions of little transistors. Transistors can only be in a state of on or off
31
Hexadecimal
- Base-16 number system
- Made up of 16 digits
32
What is a nibble?
- A group of 4 digits
- 1 hexadecimal digit can represent up to 4 digits (1 nibble)
33
Why do we use hexadecimal?
- Easier to read than binary with big numbers
- Uses less digits to store bigger numbers than binary
34
What is a bit pattern?
- A collection of binary numbers
35
Bit vs byte vs nibble vs megabyte
- 1 byte = 8 bits
- 1 nibble = 4 bits
- 1 megabyte = 1000 bytes
36
Left shift vs right shift
- Left shift multiplies by 2
- Right shift divides by 2
37
What is a bitmap?
- 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
38
How does image size and colour depth effect file size?
- 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
39
How to calculate number of colours from colour depth?
- Number of colours = 2 ^ colour depth
40
What is Huffman coding?
- A method of lossless compression used on text based documents
41
What is hardware?
- The pysical components of a computer system that you can touch
42
What is software?
- The programs that controls the hardware, live on the computer system
43
What is system software?
- Software that controls the hardware and allows other applications to run on it
- E.G: operating system
44
What is application software?
- Software added to the system that allows the user to carry out a specific task
- E.G: web browser
45
What is an operating system?
- A software that provides an interface between the user and the hardware of the computer system
46
What is user interface with examples?
- A user interface is how the user interacts with the operating system
- E.G: Graphical User Interface (GUI)
47
Memory and process management
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
What are the main roles of an operating system?
- Provide a user interface
- Memory & processor management
- I/O management & device drivers
- Application & security management
- File management
49
I/O management and device drivers
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
Application and security management
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
File management
- The OS manages where and how data is stored in both primary and secondary storage
52
What is utility software with examples?
- Software that is designed to help maintain, enhance and repair a computer system
- E.G: Task manager
53
What is defragmentation?
- 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
What is encryption?
- The process of scrambling data using an algorithm so it can only be read using a key
55
How does clock speed effect the performance of the CPU?
- The faster the clock speed, the more instructions can be fetched and executed per second
56
How does cache size effect the performance of the CPU?
- 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
How does processor cores effect the performance of the CPU?
- Multiple core processors mean they have multiple separate processing units that can fetch, decode and execute instructions at the same time - higher performance
58
What is an embedded system?
- A computer system with a dedicated function embedded in a much larger mechanical unit
- E.G: traffic lights
59
Different types of memory and their characteristics
- 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
Why do we need main memory?
- Access times are shorter than secondary storage
- Time for fetch-execute cycle is reduced
61
Why do we need secondary storage?
- Long term storage of data that is not currently in use
- Much larger capacity and easily portable
62
What is magnetic storage and its pros and cons?
- 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
What is solid state storage and its pros and cons?
- 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
What is optical storage and its pros and cons?
- 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
What is cloud storage and its pros and cons?
- 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
What is a flat file database?
- 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
What is a relational database?
- 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
What is a table, record and field?
- 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
What is a primary and foreign key?
- 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
SQL data insert
INSERT INTO table(fields)
VALUES("value")
71
SQL data update
UPDATE table
SET field = "value"
WHERE condition
72
SQL data delete
DELETE FROM table
WHERE condition
73
What is a privacy issue and some examples?
- An issue that comes from collecting, accessing or using personal information without consent or control
- E.G: face recognition, GPS
74
Examples of ethical issues
- 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
Examples of environmental issues
- 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
What is the Data Protection Act (2018)?
- 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
What is the Computer Misuse act (1990)?
- 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
What is the Copyright and Patents act (1988)?
- Protects the intellectual property of an individual
79
What is software license?
- A legal agreement that lays out the rules for how software can and can't be used
80
Pros and cons of a network?
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
What is a network?
- Two or more computers joined together with the purpose of sharing resources
82
What are the different types of network?
- 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
What are the characteristics of ethernet wires?
- Carries electrical signals between devices on a LAN
- Common in homes and offices
- Uses twisted pair cables
84
What are the characteristics of fibre optic cables?
- 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
What are the characteristics of copper cables?
- 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
What is a topology?
- 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
Star topology pros and cons
- 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
Bus topology pros and cons
- 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
Why and how do we protect a network?
- 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
What is a layer (networks)?
- 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
What is the TCP/IP model?
- 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
What is TCP/IP protocols?
- 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
What is HTTP/HTTPS protocols?
- Allows communication between servers and clients for web viewing
- Allows clients to send and receive data from a server
- HTTPS is encrypted
94
What is FTP protocol?
- File Transfer Protocol
- Allows sending and receiving files between computers
- Allows dowloading files fform the internet
95
What is IMAP and SMTP protocol?
- SMTP = allows communication between an email sender and the email server
- IMAP = allows communication between the email server and the recipient
