Paper 2 Flashcards
Ascii
- American Standard Code for Information Interchange
- A character encoding standard
- 7 bits per character - room for 128 characters (2^7)
- Can only represent English
Unicode
- 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
What is image size?
- 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
What is colour depth
- Number of bits per pixel
- The higher the colour depth, the more detailed the image is
How to calculate bitmap file size
- Image size x colour depth
How is sound digitalized
- 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
What is the sampling rate
- 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
What is the sample resolution
- Number of bits per sample
How to calculate file size (sound)
- Rate x resolution x seconds
What is the aim of compression
- To reduce file size
- Shorter transmission times, more data stored on a device
What is LOSSY data compression
- Loses some parts of the file permanantly (irreversible)
- Used for sound and images and some quality can be lost
What is LOSSLESS data compression
- Just rearranges the file to be stored in a more efficient way or encodes it in a different format
- Used for documents
- Reversible compression
How is Huffman coding done
- Gives the most frequent characters the shortest code
- Start from the top of the tree
- Binary - 1 on right, 0 on left
Run Length Encoding (RLE)
- Stores data in frequancy-value pairs
- EG: AAABBBCC = 3A3B2C
High level code
- Like written in English
- More readable
- Portable - can run on many CPUs
- Much slower
- Allow easy debugging
Low level code
- 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
What does an assembler do
- Assembley code to machine code
What does a compiler do
- High level to machine code
- Translate all of the code
- No source code needed to run
- Will not stop if errors - bad for debugging
What does an interpreter do
- High level to machine code
- Translates one line at a time
- Source code needed to run
- Will stop if error - good for debugging
Components of the CPU
- 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
Von Neumann Architecture
- Design that uses all of the CPUs components
Fetch - Exectue cycle
- 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
RAM vs ROM
- 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
Wired vs wireless network
- Wired: less prone to interferance, greater reliability and bandwidth, fixed range
- Wireless: fewer wires, flexible, easy to add more devices
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)
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
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
Data table key terms
- Record = row
- Field = column
- Primary key = uniquely identifies a record
- Foreign key = primary key from another table
SQL select query
SELECT Field
FROM Table
WHERE Condition
ORDER BY Field ASC/DESC
WHERE table.primaryKey = table.foreignKey
Why do computers use binary?
- CPUs consist of billions of little transistors. Transistors can only be in a state of on or off
Hexadecimal
- Base-16 number system
- Made up of 16 digits
What is a nibble?
- A group of 4 digits
- 1 hexadecimal digit can represent up to 4 digits (1 nibble)
Why do we use hexadecimal?
- Easier to read than binary with big numbers
- Uses less digits to store bigger numbers than binary
What is a bit pattern?
- A collection of binary numbers
Bit vs byte vs nibble vs megabyte
- 1 byte = 8 bits
- 1 nibble = 4 bits
- 1 megabyte = 1000 bytes
Left shift vs right shift
- Left shift multiplies by 2
- Right shift divides by 2
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
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
How to calculate number of colours from colour depth?
- Number of colours = 2 ^ colour depth
What is Huffman coding?
- A method of lossless compression used on text based documents
What is hardware?
- The pysical components of a computer system that you can touch
What is software?
- The programs that controls the hardware, live on the computer system
What is system software?
- Software that controls the hardware and allows other applications to run on it
- E.G: operating system
What is application software?
- Software added to the system that allows the user to carry out a specific task
- E.G: web browser
What is an operating system?
- A software that provides an interface between the user and the hardware of the computer system
What is user interface with examples?
- A user interface is how the user interacts with the operating system
- E.G: Graphical User Interface (GUI)
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
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
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
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
File management
- The OS manages where and how data is stored in both primary and secondary storage
What is utility software with examples?
- Software that is designed to help maintain, enhance and repair a computer system
- E.G: Task manager
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
What is encryption?
- The process of scrambling data using an algorithm so it can only be read using a key
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
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
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
What is an embedded system?
- A computer system with a dedicated function embedded in a much larger mechanical unit
- E.G: traffic lights
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
Why do we need main memory?
- Access times are shorter than secondary storage
- Time for fetch-execute cycle is reduced
Why do we need secondary storage?
- Long term storage of data that is not currently in use
- Much larger capacity and easily portable
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
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
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)
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
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
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
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)
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
SQL data insert
INSERT INTO table(fields)
VALUES(“value”)
SQL data update
UPDATE table
SET field = “value”
WHERE condition
SQL data delete
DELETE FROM table
WHERE condition
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
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
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
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
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
What is the Copyright and Patents act (1988)?
- Protects the intellectual property of an individual
What is software license?
- A legal agreement that lays out the rules for how software can and can’t be used
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
What is a network?
- Two or more computers joined together with the purpose of sharing resources
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
What are the characteristics of ethernet wires?
- Carries electrical signals between devices on a LAN
- Common in homes and offices
- Uses twisted pair cables
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
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
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
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
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
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
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
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
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)
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
What is FTP protocol?
- File Transfer Protocol
- Allows sending and receiving files between computers
- Allows dowloading files fform the internet
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
