⌨️Computer Science 1.1-1.6 (Paper 1) Flashcards
You can edit cards if I forgot something, flashcards based on the OCR J277 spec document
1.1.1 - What happens in the Fetch stage of the FDE cycle?
Address of next instruction is loaded into MAR and PC is incremented by 1
1.1.1 - What is the ALU and what does it do?
Arithmetic Logic Unit - performs arithmetic and logical calculations
1.1.1 - What is the CU and what does it do?
Control Unit - Decodes instructions and organises the other registers
1.1.1 - What is the cache and what does it do?
Smaller, volatile primary storage which is faster to access than the RAM and stores frequently used instructions
1.1.1 - What are registers?
Specialised units in the CPU which store one piece of information each
1.1.1 - What is the MAR and what does it do?
Memory Address Register - stores the current memory address where data is to be retrieved from or stored to
1.1.1 - What is the MDR and what does it do?
Memory Data Register - stores the data that’s been retrieved from or will be stored to memory
1.1.1 - What is the PC and what does it do?
Program Counter - keeps track of the current instruction and increments which each clock cycle
1.1.1 - What does the accumulator do?
Stores the results of calculations
1.1.1 - What is the difference between data and an address?
Data is a value used in calculations, whereas an address describes where in memory the data is stored
1.1.2 - What are the 3 factors affecting CPU speed?
Clock speed, cache size, number of cores
1.1.2 - How does clock speed affect CPU performance?
A higher clock speed means more FDE cycles can be performed every second, so the CPU performs better
1.1.2 - How does cache size affect CPU performance?
A larger cache means more instructions can be stored with a faster access time, so it takes less time to retrieve instructions on average, leading to each instruction taking less time to execute on average ==> higher CPU performance
1.1.2 - How does number of cores affect CPU performance?
More cores allow the CPU to run more FDE cycles in parallel, increasing the CPU performance
1.1.3 - What is an embedded system?
A computer system which is designed for a specific purpose, e.g. automatic thermostat in a fridge, traffic lights. It is also part of another machine or computer.
1.1.3 - What are the typical characteristics of embedded systems?
Fast and efficient, streamlined for one task, low memory capacity
1.2.1 - Why do computers have primary storage?
It is faster to access than secondary storage
1.2.1 - What is RAM and what are its characteristics?
Random Access Memory - volatile, fast access time, random access (any part of it can be accessed at any time), low storage (usually around 4-16GB)
1.2.1 - What is ROM and what are its characteristics?
Read Only Memory - non-volatile, very small (a few MB), contains the boot loader which loads the OS from secondary storage
1.2.1 - Why might virtual memory be needed in a system?
So the system doesn’t crash if it runs out of space in RAM
1.2.1 - What is virtual memory?
When the RAM is full, part of the secondary storage is used as temporary RAM - processes currently in use have priority to be in RAM
1.2.2 - Why do computers have secondary storage?
To be able to store information in a non-volatile way, i.e. it won’t get wiped when the computer switches off
1.2.2 - Name 3 types of secondary storage
Optical, Magnetic, Solid-state
1.2.2 - What are the advantages of optical storage?
Shock resistant, lightweight, portable, low cost
1.2.2 - What are the disadvantages of optical storage?
Low capacity, vulnerable to scratches, requires an external device to read/write
1.2.2 - What are the advantages of magnetic storage?
Durable, high capacity, medium cost
1.2.2 - What are the disadvantages of magnetic storage?
Moving parts so vulnerable to shocks, not very portable
1.2.2 - What are the advantages of solid state storage?
Portable (USB flash memory), high capacity, shock resistant since no moving parts
1.2.2 - What are the disadvantages of solid state storage?
High cost, limited number of read/write cycles
1.2.3 - Why is data stored in binary?
Binary can be represented by on/off switches, making calculations and storage easier and more efficient
1.2.3 - How many bits are in a nibble?
4
1.2.3 - How many nibbles are in a byte?
2 (8 bits)
1.2.3 - How many bytes are in a kilobyte?
1024
1.2.3 - How many kilobytes are in a megabyte?
1024
1.2.3 - How many megabytes are in a gigabyte?
1024
1.2.3 - How many gigabytes are in a terabyte?
1024
1.2.3 - How many terabytes are in a petabyte?
1024
1.2.3 - Order the data units from bit to petabyte
bit, nibble, B, KB, MB, GB, TB, PB
1.2.3 - How do you calculate required storage capacity given a number of files and their size?
file size x number of files
1.2.3 - How do you calculate the size of a sound file?
Duration (s) x Sample rate x bit depth (+ metadata)
1.2.3 - How do you calculate the size of an image file?
Colour Depth x Width x Height (+ metadata)
1.2.3 - How do you calculate the size of a text file?
Bits per character x Number of characters (+ metadata)
1.2.4 - What is the range of one byte of data in denary, binary and hexadecimal?
255, 11111111, FF
1.2.4 - What is the most significant bit and why?
The leftmost bit because it has the highest value
1.2.4 - What is the least significant bit and why?
The rightmost bit because it has the lowest value
1.2.4 - How do you peform a binary left shift?
Move each bit to the left, ‘chop off’ the remainder
1.2.4 - What is the effect of a binary left shift?
Multiplies the number by 2
1.2.4 - How do you perform a binary right shift?
Move each bit one place to the right, ‘chop off’ the remainder
1.2.4 - What is the effect of a binary right shift?
Divides the number by 2
1.2.4 - How are characters represented in binary?
A character set is used, so that each character corresponds to one binary value taking up a certain amount of space
1.2.4 - How is the number of different characters stored in a character set limited by the bits available?
One byte for each character only allows for 256 different values, or 256 characters, etc.
1.2.4 - Describe ASCII
ASCII uses 1B per character, allowing for 256 different characters, however only using 128, which doesn’t allow for international languages or all punctuation signs, but is more memory efficient
1.2.4 - Describe Unicode
Unicode uses 2B per character, allowing for 65,536 possible characters, allowing for all international characters and emojis, but is less memory efficient than ASCII
1.2.4 - How are character sets logically ordered?
The value of B is one more than A, the value of 7 is one more than 6, etc.
1.2.4 - How are pixels stored in binary?
Each pixel has a specific colour, represented by a specific binary code (hex codes)
1.2.4 - What is the effect of changing the colour depth of an image?
Increasing the colour depth increases the quality and increases the image size
1.2.4 - What is the effect of changing the resolution of an image?
Increasing the resolution increases the quality and increases the image size
1.2.4 - What does metadata do?
It stores additional information about the file, such as file type, image width, bit depth, etc.
1.2.4 - How is analogue sound stored in binary?
The amplitude of the sound wave is taken at specific intervals and stored as a binary value, the size of which depends on bit depth
1.2.4 - What is sample rate measured in?
Hertz (Hz)
1.2.4 - What is bit depth?
The number of bits available to store each sample in an audio file
1.2.5 - Where may compression be needed?
Transportation of files, uploading and downloading files from the internet, archiving files
1.2.5 - What are the advantages of lossy compression?
Makes the file smaller than lossless compression
1.2.5 - What are the disadvantages of lossy compression?
Some information is permanently lost; file quality decreases
1.2.5 - What are the advantages of lossless compression?
The same quality is retained
1.2.5 - What are the disadvantages of lossless compression?
File is made less small than lossy compression
1.3.1 - What is a LAN and what are its characteristics?
Local Area Network - a network of devices in a single building, or a group of buildings
1.3.1 - What is a WAN and what are its characteristics?
Wide Area Network - a network of LANs and decides across a larger area such as a region or country
1.3.1 - How does the number of connected devices affect the performance of a network?
More connected devices mean more requests sent, leading to an overall decrease in performance
1.3.1 - How does bandwidth affect the performance of a network?
Higher bandwidth means more requests and responses can be sent at once, increasing the performance
1.3.1 - How does a client-server network work?
Clients send requests to a central server, which replies with responses
1.3.1 - How does a peer-to-peer network work?
Any device can send requests or responses to any other device
1.3.1 - What hardware is needed to connect stand-alone computers in a LAN?
Wireless Access Point (WAP), Router, Switch, Network Interface Controller/Card, Transmission Media
1.3.1 - What is a WAP and what does it do?
Wireless Access Point - provides a link between wireless and wired networks
1.3.1 - What does a router do?
Transfers data packets between networks using IP addresses
1.3.1 - What does a switch do?
Connects devices together on a LAN using MAC addresses to send data packets to their destination device
1.3.1 - What is an NIC and what does it do?
Network Interface Controller/Card - hardware required for a device to join a network, has a MAC address
1.3.1 - What is transmission media?
The communication channel on a network, wired or wireless
1.3.1 - What is the Internet?
A network of computer networks spanning the entire world
1.3.1 - What is a DNS?
Domain Name Service - made up of multiple Domain Name Servers
1.3.1 - How does a DNS convert a URL to an IP address?
The domain extension is used to locate the correct domain name server, where the domain name is mapped to the URL and returned back to the client
1.3.1 - What does a web server provide?
Web pages
1.3.1 - What server provides web pages?
Web server
1.3.1 - What does a file server provide?
File storage/retrieval
1.3.1 - What server provides file storage and retrieval?
File server
1.3.1 - How do servers provide services?
The client makes a request, and they carry out their function and provide a useful response, e.g. DNS returning an IP address
1.3.1 - What is the Cloud?
When data and software is stored and run in a remote cloud server, which can be accessed at any time
1.3.1 - What are the advantages of the Cloud?
Data can be accessed from any device, less money needs to be spent on secondary storage
1.3.1 - What are the disadvantages of the Cloud?
You don’t have full control over who can access your data, can cost money, large servers are bad for the environment, data could be lost
1.3.1 - What is a star topology?
A network where each device is connected to the central server, but not to each other
1.3.1 - What is a mesh topology?
A network where each device is connected to every other device
1.3.1 - What is a partial mesh topology?
A network where each device is connected to a few other devices, i.e. multiple different pathways, but not as many as a mesh topology
1.3.1 - What are the advantages of a star topology?
Less wiring needed for wired networks, the server can filter packets and provide better security
1.3.1 - What are the disadvantages of a star topology?
If the server fails, all devices are disconnected from the network, and if one connection breaks, that device is completely disconnected from the network
1.3.1 - What are the advantages of a mesh topology?
If one connection breaks, devices can still communicate, and alternative pathways can be used if there are a lot of requests/responses
1.3.1 - What are the disadvantages of a mesh topology?
Expensive for a wired network, worse security due to multiple transmission pathways which need to be monitored
1.3.2 - Name the wired mode of connection
Ethernet – twisted pair cables
1.3.2 - Name the wireless modes of connection
Wi-Fi and Bluetooth
1.3.2 - What is the range of Wi-Fi?
100m
1.3.2 - What is the range of Bluetooth?
10m
1.3.2 - What are the advantages of wired networks?
Better security, faster, higher bandwidth
1.3.2 - What are the disadvantages of wired networks?
Lots of cables can be expensive, harder to rewire the network or add/remove devices
1.3.2 - What are the advantages of wireless networks?
Easy to add/remove devices, no cables required
1.3.2 - What are the disadvantages of wireless networks?
Poorer security, multiple WAPs may be needed due to limited range, slower, lower bandwidth
1.3.2 - What is encryption?
Scrambling of data using a key to prevent interception across network connections
1.3.2 - What is an IP address?
The address of a LAN used by routers to communicate across the Internet
1.3.2 - Name the two IP standards
IPv4 and IPv6
1.3.2 - How are IP addresses formatted?
IPv4 is 32 bits; IPv6 is 8 groups of 4 hexadecimal digits
1.3.2 - What is a MAC address?
The local address of a device in a LAN – used by the switch
1.3.2 - How is a MAC address formatted?
48 bits, usually represented as a string of 12 hexadecimal digits (6 pairs separated by colons)
1.3.2 - What is a standard?
A way to format addresses, etc. to provide global rules for areas of computing
1.3.2 - What does a standard allow?
For different hardware/software made by different manufacturers/producers to be able to communicate
1.3.2 - Name the 7 common protocols
TCP/IP, HTTP, HTTPS, FTP, POP, IMAP, SMTP
1.3.2 - What is TCP/IP and what is it used for?
Transmission Control Protocol/Internet Protocol - Communication across the Internet
1.3.2 - What is HTTP and what is it used for?
Hyper Text Transfer Protocol - transferring files over the Internet
1.3.2 - What is HTTPS and what is it used for?
Hyper Text Transfer Protocol Secure - transferring secure files over the Internet and uses encryption
1.3.2 - What is FTP and what is it used for?
File Transfer Protocol - transfer of files in a client-server network
1.3.2 - What is POP and what is it used for?
Post Office Protocol - accessing messages from the Internet - messages are deleted from the mail server after a copy is sent to the requesting client
1.3.2 - What is IMAP and what is it used for?
Internet Message Access Protocol - accessing messages from the Internet - messages are not deleted from the mail server after a copy is sent to the requesting client, allowing for access from multiple devices
1.3.2 - What is SMTP and what is it used for?
Simple Mail Transfer Protocol - sending messages across the Internet
1.3.2 - What is layering?
Different levels of a network only have to access or change certain information, without needing access to other information, e.g. the 4 layer TCP/IP model
1.3.2 - Why is layering useful?
It allows software developers to specialise and work on their own areas without having to worry about other parts, like decomposition
1.4.1 - What is malware?
Software used to compromise or break into a system
1.4.1 - What is social engineering?
Using people as the weak point in a network, manipulating them into giving away important information
1.4.1 - What is a brute-force attack?
Trying every possible password to try and hack into a system
1.4.1 - What is a dictionary attack?
Trying every potential password in a set list, e.g. words in a dictionary, to try and hack into a system
1.4.1 - What is a DoS attack?
Denial of Service - flooding a network with useless requests to shut it down
1.4.1 - What is a DDoS attack?
Distributed Denial of Service - flooding a network with useless requests from multiple sources to shut it down
1.4.1 - What is data interception/theft?
Intercepting data as it is transmitted, usually through packet sniffing, to gain unauthorised access to important company files
1.4.1 - What is SQL injection?
Pasting code into an input box to get the system to do something else, e.g. return a list of all usernames and passwords in a company
1.4.1 - Name the different forms of attack
Malware, Brute force, Dictionary, DoS, DDoS, Data interception (packet sniffing), SQL injection
1.4.2 - Name the ways to prevent attacks
Penetration testing, Anti-malware software, Firewalls, User access levels, Passwords, Encryption, Physical Security
1.4.2 - How does penetration testing prevent attacks?
It allows companies to identify and fix security weaknesses before they are found by hackers
1.4.2 - How does anti-malware software prevent attacks?
It stops malware from harming the network
1.4.2 - How do firewalls prevent attacks?
They stop malware entering the network and doing damage
1.4.2 - How do user access levels prevent attacks?
They make sure as few people have access to important files as necessary, reducing the chance of them escaping
1.4.2 - How do passwords prevent attacks?
They reduce the likelihood of unauthorised access to important files
1.4.2 - How does encryption prevent attacks?
It stops intercepters from being able to read important files when they’re being transmitted
1.4.2 - How does physical security prevent attacks?
It prevents attackers from being able to access important information physically, e.g. walking into the data centre with a USB stick
1.5.1 - Name the parts of an operating system
User interface, Memory management & multitasking, Peripheral management & drivers, User management, File management
1.5.1 - What does a user interface do?
It provides an interface through which the user can control the computer and navigate its systems
1.5.1 - What are the features of a user interface?
WIMP model - Window, Icon, Menu, Pointer
1.5.1 - What does memory management do?
It manages the transfer of data between memory, the allocation of memory to applications, and multitasking
1.5.1 - What is multitasking?
Quickly switching between processes to give the illusion of them happening simultaneously
1.5.1 - What does peripheral management do?
It manages the transmission of data between the computer and its peripherals, e.g. printers, keyboard
1.5.1 - What do device drivers do?
They allow peripherals made by different manufacturers to still be able to communicate with the computer in a language both the computer and peripheral can understand
1.5.1 - What does user management control?
The allocation of an account, Access rights and Security
1.5.1 - What does file management control?
Naming files, Allocating files to folders, Moving files, Saving files, etc.
1.5.2 - Name the types of utility software
Encryption, Defragmentation, Data compression
1.5.2 - Why is encryption software needed?
To allow secure transmission and prevent sensitive information being intercepted
1.5.2 - What is defragmentation software?
Rearranging secondary storage so it is in order and all the empty space is at one end
1.5.2 - Why is defragmentation software needed?
To reduce read/write time - only for hard disk drives with moving parts, provides no benefit for solid state drives
1.5.2 - Why is compression software needed?
To allow for more efficient storage and faster uploading of files to the Internet
1.5.2 - Why is utility software needed?
To perform tasks which may not be carried out by the operating system
1.6.1 - Name the different issues with digital technology
Ethical, Legal, Cultural, Environmental, Privacy
1.6.1 - When was the Data Protection Act?
2018
1.6.1 - What did the Data Protection Act do?
Protects personal data - it must be fairly & lawfully processed, obtained for specific purposes, adequate & relevant, accurate & up to date, kept for no longer than necessary, processes in line with your rights, and held securely
1.6.1 - When was the Computer Misuse Act?
1990
1.6.1 - What did the Computer Misuse Act do?
It makes it illegal to seek or gain unauthorised access to computer material, steal data or destroy information unauthorised, modify data unauthorised, and make or supply anything to allow the above
1.6.1 - When was the Copyright Designs and Patents Act?
1988
1.6.1 - What did the Copyright Designs and Patents Act do?
It gives creators of digital media the rights to control how their work is used and distributed
1.6.1 - What is software licensing?
Proprietary software can only be used or distributed with a license
1.6.1 - What are the advantages of open source software?
Free, source code can be accessed and modified, support provided by the community
1.6.1 - What are the disadvantages of open source software?
May not be fully tested, may not have extensive support
1.6.1 - What are the advantages of proprietary software?
Will be extensively tested and supported, will be regularly patched
1.6.1 - What are the disadvantages of proprietary software?
Need to pay for a license, can’t access the source code
