GCSE OCR (J277) Computer Science: Paper 1

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  • Created by: Knaresh
  • Created on: 23-01-22 18:50
What is a computer?
An electronic device that takes input, processes data and delivers output
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What is the purpose of the CPU?
To fetch, decode and execute instructions
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What is the purpose of the ALU?
To perform arithmetic calculations and logical operations
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What is the function of the CU?
Sends signals to control how data moves around the CPU
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What are registers?
Tiny, super fast pieces of memory inside the CPU that temporarily store data before it's processed
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What is the function of the PC?
To hold the address of the next instruction that is to be process
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What is the function of the MAR?
Holds the address of where data is to be fetched or stored
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What is the function of the MDR?
Holds data to be written to or fetched from memory
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What is cache memory?
High speed memory in the CPU that provides fast access to the most frequently used programs and instructions
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What happens during the fetch stage of the FDE cycle?
Address in PC copied to MAR. Instruction at that address is fetched from RAM and copied into MDR
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What is meant by clock speed?
How many instructions can be processed per second (Hz)
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What is a core?
A processor of the CPU
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Why might multiple cores increase CPU performance?
More power to run multiple programs at once
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Why might several cores not always help CPU performance?
Cores have to communicate with each other - takes time. Not all programs are designed to utilise multiple cores.
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What is an embedded system?
A system with a dedicated function within a larger mechanical system.
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What are the key features of embedded systems?
Low cost per unit, small size, low power consumption, rugged operating range
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Examples of embedded systems?
Traffic lights, dishwashers, washing machines
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Examples of primary storage?
RAM, ROM, Cache
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What does primary storage hold?
Data and instructions that CPU needs access to while computer is running
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What does RAM hold?
Operating system, programs and data in use by the CPU while the computer is running
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What does ROM hold?
Bootstrap: first instructions for computer when it's turned on
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What are the differences between RAM and ROM?
RAM is volatile; ROM isn't. RAM is read and write; ROM is read-only. RAM has a larger capacity than ROM.
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What is virtual memory?
A section of secondary storage used as RAM, when RAM is full and can't store open programs.
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What is paging?
Slow process of swapping programs between RAM and ROM depending on when they're needed.
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Why is secondary storage important?
ROM is read-only and RAM is volatile.
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What is secondary storage needed for?
Storage of programs and data when the computer is switched off. Backup and archive of data files.
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Examples of optical storage?
CD, DVD, Blu-ray
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Features of optical storage?
Low capacity; slow-access; thin, lightweight and portable
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Examples of magnetic storage?
HDD, Floppy disk, Magnetic tape
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Features of magnetic storage?
High capacity, quick-access; moving parts - so will eventually fail
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Examples of solid-state storage?
SSD, Flash Memory Cards
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Features of magnetic storage?
Medium capacity, very quick access, reliable - no moving parts, low power, expensive, no need to defragment, limited read-write cycles
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How do we calculate the file size of a text file?
Bits per Character X Number of characters
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How do we calculate the file size of an audio file?
Sample Rate X Duration X Bit Depth
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What is meant by sample rate?
How many samples (recording of amplitude) is taken per second
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What is meant by bit depth?
Number of bits needed to store each sample
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How do we calculate file size of an image file?
Colour depth X Image width X Image height
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What is meant by colour depth?
The number of bits needed to store each pixel
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What is a character set?
A defined list of characters recognised by the computer, each character is represented by a unique binary number?
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How many bits does ASCII use?
7
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How many bits does extended ASCII use?
8
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How many bits does unicode use?
16
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How are bitmaps constructed?
From coloured shapes (pixels that are stored in binary)
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How are vector images drawn?
Maths used to draw coloured shapes
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What is metadata?
Additional information about an image, it's stored with the image
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What does file size of an image depend on?
Colour depth, resolution
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What is the colour depth of photographs, and image in the human eye?
24
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What increases file size and quality of an audio file?
Sample rate and bit depth
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What does compression do?
Reduces the number of bits in a file?
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What is the purpose of compression?
Free up storage capacity and increase data transfer speed
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What are the features of lossy compression?
Data is lost and can't be recovered, relatively high reduction; quality compromised; suitable for images, sound and video; can't be used on texts and programs
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What are the features of lossless compression?
No data lost; reversible; less reduction than lossy; suitable for documents and executable files; can be used for all file formats
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What are the advantages of using networks?
Files and peripherals can be shared; files can be accessed from any node; servers can control security, updates and backups; easy to communicate with others on a network
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What are the key features of a LAN?
Small geographical area, single site; organisation owns all hardware; connected with fibre-optics, UTP or wirelessly
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What are the key features of a WAN?
Large geographical area; collection of LAN's; infrastructure between LAN's leased from telecommunications company; connected with telephone lines, satellites, fibre-optics
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What are the disadvantages of networks?
Increased security risk to data; malware and viruses spread more easily; if server fails computers connected to it may not work; network traffic decreases performance of network
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What is bandwidth (bits per second)?
Amount of data that can be send and received successfully in given time.
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What is error rate of a network dependent on?
Reliability of connections; signal quality (environment and quality of copper affects this); length of cable
Data has to be resent until it arrives correctly
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What is latency?
Dekay from transmitting data to receiving it
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What is latency caused by?
Bottleneck
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What affects network performance?
Bandwidth, transmission medium, error rate, latency
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How does a client-server network model work?
Client makes requests to server for data nd connections; the server controls security, Internet access, printing, emails and backup
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What are the advantages of a client-server network model?
Easy to centrally manage security, backups and updates
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What are the disadvantages of a client-server network model?
Expensive to set up and maintain - IT specialist needed; server is single failure point
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What is a peer?
A computer on a network that is equal to other computers on a network
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How does a peer-peer network work?
Peers serve own files to each other and are responsible for own security and backup
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What are the advantages of a peer-peer network?
Easy to maintain, no IT staff needed; no dependency on single computer; cheaper to set up - no need for expensive hardwrae
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What are the disadvantages of a peer-peer network?
Less secure; backups and files can't be centrally managed
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What is the function of a NIC?
To connect a device to a network, uses a protocol to ensure a successful communication
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What is the function of a WAP?
Allows wireless connections to a network
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What is a switch?
Device that sends data between computers on a LAN, uses NIC address to direct traffic
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What does a router do?
Sends data between networks; connects LAN to WAN; uses IP address to route traffic to other routes
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What are Unshielded Twisted Paid (UTP) cables used for?
Copper cables connect desktop computers to switch
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What are the features of copper cables?
Cheap, flexible, easy to install
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What are the advantages of fibre-optic cables?
Long distances, high bandwidth, less interference
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What is the Internet?
Global collection of interconnected networks
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What does a DNS do?
Converts web addresses to IP addresses
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What is hosting?
Storing a website on a server?
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Why do people use website hosting companies?
24/7 access; multiple users; greater security
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What is meant by Cloud Storage?
Remotely storing data and programs over the Internet
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What is a Star Network topology?
Network where every device connected to central switch that makes sure traffic only goes where intended
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What are the advantages of a star network?
If cable breaks, only 1 computer is affected
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What are the disadvantages of a star network?
Switch is a single point of failure
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What is a full mesh network?
Every device connected to every other device
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What is the advantage of a full mesh network?
Traffic can still be routed with a break in connection
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What is the disadvantage of a full mesh network?
Cabling costs money
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What are the advantages of wireless networks?
Convenient, easy to set up, cheap; large numbers of users can connect
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What are the disadvantages of wireless networks?
Slower and less secure than wired networks; signals can be obstructed; relies on signal strength to WAP
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What are MAC addresses used for?
Routing frames of LAN's
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What are IP addresses used for?
Routing data packets on WAN
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What is a protocol?
Set of rules that allows 2 devices to communicate
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What does TCP do?
Provides error free transmission between 2 routers
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What does IP do?
Routes packets across WAN
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What does HTTP do?
Requesting and delivering HTML pages
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What does HTTPS do?
Requesting and delivering HTML pages, with authentication and encryption
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What does FTP do?
Sends files between computers
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What does POP do?
Retrieves emails from server and deletes emails from server
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What does IMAP do?
Retrieves emails from mail server
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What does SMTP do?
Sends emails to email server
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What is the concept of layering?
To divide complex tasks into simpler tasks, each layer has a responsibility, and service to layer above it
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What are the advantages of layering?
Complex problems broken down into simpler problems; devices can be manufactured to work at specific layer
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What is malware?
Software designed to disrupt, damage or gain unauthorised access to a computer system
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What threats does malware pose?
Files deleted, corrupted or encrypted; computers crash, slow down or reboot; internet connections are slow; keyboard inputs are logged
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How can we protect against malware?
Firewall, spam filter, anti-virus, anti-malware, anti-spyware, anti-spam, security software updates, staff training, regular backups
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What is phishing?
Fraudulently sending emails pretending to be from reputable company, but trying to get users to reveal private information
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What threats do phishing pose?
Purchases made with your money, reputation damaged
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How can we protect against phishing?
Strong security software, awareness of fake emails, don't disclose personal information, disable browser pop-ups
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What is a brute force attack?
Automated software used to generate password guesses
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What threats do brute force attacks pose?
Data thefts, security of systems compromised
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How do we protect against a brute force attack?
Strong passwords, lockout policy, reCAPTCHA
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What is a denial of service attack?
Flooding server with useless traffic to make server overloaded and unavailable
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What threats do a DoS attack pose?
Reputation, profits and productivity compromised
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How do we protect against a DoS attack?
Strong firewall, packet filters, monitor systems
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What is a data interception and theft attack?
Unauthorised act of stealing computer-based information from a victim
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What threats do data interceptions and thefts pose?
Unauthorised access to a system is given and privacy is compromised
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How do we protect against data interception and theft?
Encryption, virtual networks, investigate network weaknesses, staff training
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What is an SQL injection attack?
Code inserted into input box to try and change database data
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What are the threats of an SQL injection attack?
Private data can be revealed and changed; rogue records may be added
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How do we protect against SQL injection attacks?
Validation on input boxes, parameter queries, database permissions, penetration testing
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How are people a weak point to network security?
Leaving passwords on sheets of paper; not updating anti-malware; not encrypting
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General ways to protect a network?
Anti-malware, encryption, firewalls, penetration testing, Strong passwords, Physical security, user access levels
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What are the key features of a GUI?
WIMP; visual, interactive; optimised for mouse and touch-based interface
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What are the key features of a CLI?
Text based; less resource heavy than GUI; more command; good for advanced users; can automate processes
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What are the features of a menu interface?
Successive menus presented to user and single options chosen at each menu
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What are the features of an NLI?
Unreliable; useful when can't touch device
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What are the features of an operating system?
Memory management, multitasking, device drivers, file management, user management
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What is multitasking?
Running several applications at once by giving each application a small time slice of processor time
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Why is multitasking useful?
More programs can be held in memory at once and data can be shared between programs
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What is the role of the OS in memory management?
OS decides where programs are held in memory. It keeps track of data fragments.
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What do device drivers do?
Translates OS instructions into commands that hardware will understand
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What is the role of the OS in user management?
Allows different users to log into computer with settings retained for each user
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What is the role of the OS in file management?
Allows user to edit, rename and delete files. Responsible for opening files.
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What are the features of utility software?
Disk defragmentation, Encryption, Data compression
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What is encryption?
Algorithm that scrambles plain text into cipher text
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How does defragmentation increase file access speed?
Fragments of fikes put back together and free space grouped together. Read/write head movement decreases.
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Arguments for why the Internet should be regulated?
Contains, harmful, illegal and offensive content; children should be protected
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Arguments for why the Internet should not be regulated?
Right to Freedom of Expression; hard to censor; censoring bad for democracy; responsibility on users
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Privacy issues of computer science?
Face recognition, browser history, smart listening devices
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Cultural issues of computer science?
Digital divide, censorship
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What are the environmental issues of computer science?
Technology shipped to developing countries for disposal; greenhouse gas emissions
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Who are stakeholders?
Individuals or groups who are affected by a scenario
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What does the Data Protection Act state?
Data should be processed fairly, lawfully and securely; data should only be collected for specified reasons; collected data should be relevant, necessary, accurate and adequate; data controllers should prove date privacy measures are sufficient
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What does the Computer Misuse Act state?
Illegal to access data with intent to commit further offences or to modify data
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What does the Copyright, Designs and Patents Act state?
Illegal to copy, modify or distribute software without author's permission
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What are the key features of open source software?
Can be modified and distributed; can be installed on any number of computers; support provided by community; users have access to source code; not always fully tested
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What are the key features of proprietary software?
Users can't modify software; paid for per device/user; supported by developers; no access to software; tested
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Other cards in this set

Card 2

Front

What is the purpose of the CPU?

Back

To fetch, decode and execute instructions

Card 3

Front

What is the purpose of the ALU?

Back

Preview of the front of card 3

Card 4

Front

What is the function of the CU?

Back

Preview of the front of card 4

Card 5

Front

What are registers?

Back

Preview of the front of card 5
View more cards

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Naz867

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can you make paper 2?

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