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What is the concept of the Von Neumann architecture?
The CPU recieves instructions or data from an input or memory. There is a single memory and bus system for accessing both data and programs.
The instructions or data are processed by the CPU and are either sent to an output or transferred to secondary storage.
What are the key elements of the Von Neumann architecture
Data and instructions are both stored as binary and in main memory.
Instructions are sequentially fetched from memory one at a time.
The processor decodes and executes an instruction before cycling around to fetch the next instruction.
The cycle continues until no more instructions are available.
What are the major components of a central processing unit that responds to and processes the instructions that drive the computer within the Von Neumann architecture?
Arithmetic logic unit
Control unit
Clock
Register
Cache
Bus
Explain the role and operation of the arithmetic logic unit within the Von Neumann architecture
The ALU carries out these functions:
Logical operations (AND, OR, NOT)
Shift operations (Binary shifts)
Arithmetic operations (addition, multiplication)
Explain the role and operation of the control unit within the Von Neumann architecture
The control unit fetches, decodes and executes instructions inside the CPU:
ensures the execution of instructions is in the correct sequence and decodes them
sends control signals that control hardware
regulates processor timing using regular pulses from the system clock
sends and recieves control signals from other devices within the computer
Explain the role and operation of the clock within the Von Neumann architecture
The clock coordinates processor timing and CPU operations. The clock sends out a regular electrical pulse which synchronises all the components.
The clock frequency is the number of clock cycles occuring each second (Hz)
Explain the role and operation of the register within the Von Neumann architecture
A register is a high speed memory location within the CPU that stores small amounts of data needed during processing, e.g. results of calculations or the current instruction being decoded.
Explain the role and operation of cache within the Von Neumann architecture
Cache is a small amount of high-speed random access memory (RAM) built directly within the processor. It is used to temporarily hold data that the processor is likely to reuse.
It allows faster processing as the processor doesn’t have to wait for data and instructions to be fetched from the RAM.
Explain the role and operation of a bus within the Von Neumann architecture
A bus is a high-speed internal connection that sends control signals and data between the processor and other components. It is a collection of wires through which data/signals are transmitted from one component to another.
Data is passed along buses, which are collectively referred to as the system bus.
What are the 3 factors affecting CPU performance?
Clock speed
Number of processor cores
Cache size
How does clock speed affect CPU performance?
Clock speed is the number of pulses the CPU clock generates per second, measured in Hertz.
The more pulses per second, the more fetch-decode-execute cycles can be performed and the more instructions are processed.
The greater the clock speed, the faster instructions are executed, the greater the CPU performance.
How does cache size affect CPU performance?
The more cache memory a computer has, the more the data can be held in cache, so the less time a processor has to wait for instructions to be fetched from main memory RAM as more instructions are in high-speed cache memory instead, so the less time it takes to fetch instructions and data as it is quicker to fetch from cache than it is from RAM so the better the CPU performance.
How does number of processor cores affect CPU performance?
A processing unit within a CPU is known as a core. Each core is capable of fetching, decoding, and executing its own instructions.
The more cores a CPU has, the greater the number of instructions in can process in a given space of time.
Explain the fetch-decode-execute cycle that the processor uses to run a program
The CPU continually reads instructions stored in main memory and executes them as required.
Fetch: The next instruction is fetched from the main memory to the CPU
Decode: The instruction is decoded to work out what it is
Execute: The processor executes one instruction at a time. This may involve reading/writing to main memory
What is the difference between main memory and secondary storage?
Main memory is any form of memory directly accessible by the CPU (except for cache and registers).
Secondary storage is any non-volatile storage not directly accessible by the CPU.
Any data needed for a program to be executed needs to be loaded from secondary storage into RAM for the processor to access the instructions.
What are the two types of main memory?
RAM (Random access memory) and ROM (Read only memory)
What does volatile mean?
Volatile memory is temporary. Data and instructions are lost once power is turned off.
Non volatile memory is used for long-term storage and secures data and instructions even when power is lost.
What is RAM used for?
RAM is volatile main memory. It is called Random Access because data can be stored and accessed from any location within the memory.
The main purpose of RAM is to act as temporary storage for programs that are currently being executed.
It can be read from and written to, the contents can be changed at any time.
The more RAM a computer has, the more data and programs it can hold simultaenously.
What is ROM used for?
ROM is non-volatile main memory. It can be read from but not written to. You cannot write over the contents of ROM.
It is ideal for storing instructions and data needed to start a computer- the Basic Input Output System that runs as soon as the computer is switched on. The computer would not be able to start if the BIOS was volatile.
What are the key differences between RAM and ROM?
RAM is volatile temporary memory, ROM is non-volatile permanent memory.
RAM stores data and programs currently in use, ROM stores the BIOS which is required at the start-up of the computer.
RAM can be read from AND written to, ROM is only read from and cannot be written to.
Why is secondary storage required?
Computers need to store programs and data for later use. Non-volatile memory is needed for long-term use, e.g. photos, projects.
However, embedded computers don’t require secondary storage, e.g. in washing machines they do not need to store data when power is turned off. The instructions needed to run the system is in ROM and any user data is temporary not-long term and so held in RAM.
What are the 3 types of secondary storage?
Solid state storage e.g. USB memory sticks
Optical storage e.g. CDs and DVDs
Magnetic storage, e.g. Hard disk drives
Secondary storage is non-volatile, but can be read from AND written to.
Explain the operation of solid state storage
Solid state drives use electrical circuits to persistently store data.
It has no moving parts, so its portable and durable
Faster to access than magnetic storage
Lightweight, ideal for phones and tablets
More expensive than magnetic storage
Explain the operation of magnetic storage
Magnetic disks are read with a moving head inside the disk drive. Each section of a metal disk represents 1 bit. A magnetised section represents a binary ‘1’ and a demagnetised section represents a binary ‘0’
Moving head makes it slow to read from and write to
Moving head makes it more susceptible to damage
Vulnerable to magnetic fields
Cheaper than solid state storage
Huge capacity
Explain the operation of optical storage
Optical devices ue a laser to scan the surface of a spinning disc. The laser bounces light onto the surface which is covered in pits and lands. A sensor detects reflected light. Non-reflective pits are a binary ‘0’ and reflective lands are a binary ‘1’
Cheap to produce
Lightweight, easy to distribute
Can be corrupted or damaged easily by excessive sunlight or scratches
Define the term cloud storage
Storing data in magnetic/solid state storage at a remote location is known as cloud storage. Files can be uploaded and downloaded to these servers as required.
What are advantages of cloud storage when compared to local storage?
Data can be easily accessed from anywhere with an internet connection
Data can be shared more easily than sharing data stored locally
Additional storage and be added easily without having to invest in additional hardware with local storage
Backup is not an issue, as it is the responsibility of the provider to protect the data
What are disadvantages of cloud storage when compared to local storage?
You are dependent on an internet connection to access your data
Users are concerned about security, data can be easily attacked by a hacker with an internet connection
Define an embedded system
An embedded system is a small computer that forms part of a larger system, device or machine. They tend to have a limited number of tasks they can perform.
Explain the difference between an embedded system and a non-embedded system. Give examples of both.
Embedded system software is custom-written to work for specific hardware. Non-embedded systems are more general purpose.
Their limited functions mean they are cheaper to build.
They require less processing power, so less power overall, and so some run on batteries.
Examples of embedded systems- dishwashers, electronic calculators, central heating systems
Examples of non-embedded systems- software in a PC, dedicated servers
Define a computer network
A network is the connection of computers for the purpose of communication. This can be through a wired medium, e.g. wires, or a wireless medium, e.g. Wi-Fi
What are advantages of computer networks?
Resource sharing- users can share peripheral devices, e.g. printers, and can distribute software, reducing costs
Communication- allows collaboration
Roaming access- users can sign into any computer on the network and access their files
Centralised updates and security
Scalability- networks can be easily expanded to accommodate growing needs
What are disadvantages of computer networks?
Risk of viruses spreading across a network
Expensive hardware
More difficult to manage larger networks
Performance degrades as network traffic increases
What are the three main types of computer networks?
Personal Area Network (PAN)
Local Area Network (LAN)
Wide Area Network (WAN)
Describe a Wide Area Network (WAN) and give an example
A WAN is spread over a wide geographical area. They tend to be under collective or distributive ownership due to the extremely high cost.
The internet is the biggest example of a wide area network.
Describe a Local Area Network (LAN) and give an example
A LAN covers relatively small geographical areas. It consists of a collection of computers and peripheral devices connected together on a single site. It is often owned and managed by a single person or organisation.
Examples include schools and colleges.
Describe a Personal Area Network (WAN) and give an example
A PAN is spread over a very small area. It covers no more than a few metres and is used for data transmission amongst personal devices such as a keyboard and a computer.
Bluetooth is an example of a personal area network.
Give 4 advantages of wireless networks
Users can move around freely within the area of the network without being disconnected
Users can share files without needing to be connected to a port
Cheaper and easier than having to install cables through walls
Easier to add new devices
Give 3 disadvantages of wireless network
Connection can be obstructed by walls and furniture
Less secure and easier to hack into as no physical connection is needed to intercept data
Susceptible to interference from other wireless devices or networks
Give 4 advantages of wired networks
More secure and harder to hack into as a physical connection is needed to intercept the data
No interference from other networks
Faster transfer speeds
Can support larger amounts of data
Give 4 disadvantages of wired networks
Installation costs can be expensive and requires space
User is restricted to physical connections and cannot move freely
Harder to add new devices than wireless networks- limited scalability
Susceptible to damage from environmental factors or construction work
Explain the different types of cable wired networks can use and when each would be appropriate
Copper and Fibre optic cables
Fibre optic cables are made of thin, flexible glass. It is a fast connection and the cables take up little space. Fibre optic cables have a higher bandwidth than copper, and it is harder to intercept the connection between devices.
However, they are more expensive to install than copper.
Copper cables are more robust, and are cheaper to install. However, they are at risk of corrosion and the electric signals are susceptible to interference, so the signal degrades as it travels along the wire, and it has a slower connection than a fibre optic connection. They are widely used in LANs because the slow speed is adequate and affordable.
What is a LAN network topology? Explain it using the term ‘node’
Any device connected to a network is referred to as a node.
A network topology is the arrangement in which the nodes on a network are connected together. They are commonly used in LANs.
The two types of topologies are bus and star topologies.
How are nodes and connections represented on a network topology diagram?
Nodes are squares.
The connection between devices is a straight line.
Describe a star topology diagram and when it is used
In a star topology, there is a central switch and all nodes are connected to this one central switch with their own cable. The switch routes messages to the correct computer, and all communications are passed through this switch.
Star topologies are used when the network needs to be reliable and secure, where fast speeds and high performance are important (message is passed to intended node only so faster and quicker) e.g. in schools and large organisations
A wireless router is an example of a switch
State the advantages of a star topology
Each node is seperately connected with its own cable, so the disconnection and failure of one cable doesn’t impact the rest of the network
Consistent performance even when the network is heavily used
New nodes can be added just by connecting them to the switch
High performance as message is passed onto intended node only- fast, reliable secure
State the disadvantages of a star topology
Network is dependent on the switch, if the switch fails then no node can communicate
A wired star topology would require a lot of cables which can be expensive in a large network (wouldn’t impact wireless star topologies)
Describe a bus topology diagram and when it is used
A bus topology consists of one long cable with terminators at either end. Every node is connected to this one long cable with their own seperate cable. This central cable is known as the backbone.
Data is sent up and down the backbone until it reaches the correct node, and each node determines whether it is the right data using its unique identifier.
Bus topologies are used when there are only a few computers as they are not suited to dealing with large amounts of data. They are used for small, cheap, temporary networks that don’t need high data transfer speeds.
State the advantages of a bus topology
Easy to connect nodes to the network
Cheap to install as less cabling than in a star topology
State the disadvantages of a bus topology
Network depends on the backbone cable, whole network fails if backbone cable is broken
Terminators need to be installed
Increased chance of data collisions since all data travels along the central cable. Large amounts of network traffic causes more data collisions, so the network slows down if many devices are connected
Security risk, since all data travels along the central cable, so other nodes can “see” it
Define network protocol
Network protocol is the set of rules that define how devices communicate and governs the transmission of data. These rules include the format of data packets, error-checking procedures, and how to locate another node on the network.
State the 10 common types of network protocol using their sub-categories
Connection protocols- Ethernet, Wi-Fi
Transmission protocols- TCP, UDP
Addressing protocol- IP
Transfer protocols- HTTP, HTTPS, FTP
Email protocols- SMTP, IMAP
What is the purpose of the connection protocol Ethernet
Ethernet is a family of related protocols rather than a single protocol. It governs how data is sent along ethernet cables, including how hardware is managed, how data is sent and recieved, and how data collisions are managed.
What is the purpose of the connection protocol Wi-Fi
Wi-Fi is a family of related protocols rather than a single protocol. Wi-Fi is a trademark, and the generic term for networks of this nature is WLAN (wireless local area network)
Any device with Wi-Fi uses the Wi-Fi protocol which determines how devices connect wirelessly to other Wi-Fi enabled devices.
What is the purpose of the transmission protocol TCP/Transmission Control Protocol
TCP defines how messages are broken into packets and reassembled at the destination. TCP is more widely used and more reliable than UDP. TCP detects errors and resends lost packets.
What is the purpose of the transmission protocol UDP/User Datagram Protocol
UDP is an alternative to TCP, but doesn’t use packets or error checking. It is a lot quicker as it sends everything at once instead of using packets, but it doesn’t correct data that didn’t reach. It is often used for online-gaming where quality is less important than speed.
What is the purpose of the addressing protocol IP/Internet Protocol
When a device is connected to the internet, it is assigned an IP address. The IP protocol identifies the location of a device on the internet and ensures each data packet has sender and reciever IP addresses. It works alongside the TCP transmission protocol to ensure data is sent securely across the internet.
What is the purpose of the transfer protocol HTTP/Hypertext Transfer Protocol
HTTP is used for accessing and recieving web pages on the internet. The protocol requests the web server to transmit the requested web page to the user’s browser for viewing. Websites on the World Wide Web are packaged using the HTTP protocol.
What is the purpose of the transfer protocol HTTPS/Hypertext Transfer Protocol Secure
HTTPS serves the same pupose as HTTP, but it provides an encrypted version of HTTP for more secure web transactions and for the transmission of sensitive data.
What is the purpose of the transfer protocol FTP/File Transfer Protocol
FTP is used to upload or download files on the internet, transferring files on a network.
What is the purpose of the email protocol SMTP/Simple Mail Transfer Protocol
SMTP is used to send email messages between servers around the world.
What is the purpose of the email protocol IMAP/Internet Message Access Protocol
IMAP controls the download/upload of emails to and from the email server. It allows users to create a copy of emails locally, organise folders, and save draft messages. It allows drafts to be viewed on email servers across devices.
Explain the need for and the importance of network security
Networks are more vulnerable to hackers than standalone devices as a hacker may access multiple devices on the same network. This can have serious implications for an organisation, resulting in malware being installed, data theft or unauthorised access to data.
Network security must also ensure that authorised people can access the resources they need and are not interrupted by hackers
What are the 4 methods of network security?
Authentication, encryption, firewall and MAC address filtering
These methods can be used together to provide a greater level of security than using them in isolation
Explain what authentication is and when it should be used
Authentication is the process of identifying users with permission to access the network and users who are unauthorised. An organisation must ensure that users have permission to see and use data on a network.
This can be through knowledge, e.g. a password or answer to a question, or a physical item such as biometrics or a swipe card. These can be combined to create a secure login to a system.
Different levels of authentication can be used depending on the security level required, e.g. two-step authentication.
Administrators can also set access rights, which grant different users access to different areas, e.g. a boss might have access to all areas, whereas a guest account may have limited access, protecting the company’s data.
Explain what encryption is and when it should be used
Encryption disguises data so that it cannot be understood by anyone but its intended recipient. It does not prevent someone from intercepting a message, only from understanding it. The key is only available to authorised users.
Encryption can be used for communication, e.g. end-to-end encryption, and alongside authentication where data is unencrypted upon entering a password.
Explain what firewalls are and when they can be used
A firewall is software that monitors incoming and outgoing network traffic, and blocks unexpected connections. It decides whether to allow or block specific traffic based on a defined set of security rules decided by the network manager.
The capabilities of firewalls have changed dramatically in recent years and will continue to do so.
Explain what MAC address filtering is and when it can be used
Every device has a unique MAC address embedded within the device’s network adapter, allowing individual devices on a network to be identified easily. A network manager can choose which devices are blocked and which have access using this address, known as MAC address filtering.
However, although it identifies the permitted devices, it does not identify who is using that device. This is why MAC address filtering is most effective alongside authentication.
What is the 4 layer TCP/IP model? What are the benefits of 4 layers?
TCP and IP are protocols that control communication through the internet. They work together in the TCP/IP model to ensure messages sent from one computer to another arrive securely.
Each layer is responsible for different parts of the communication process. The layered design lets suppliers easily adapt the protocol software to specific hardware and operating systems, e.g. software for an ethernet system can be adapted for an optical fibre system just by changing the link layer
What are the four layers of the TCP/IP model?
Application layer
Transport layer
Internet layer
Link layer
Packets of data are passed down through the layers which each perform their individual functions before the data packet is transmitted across the network. At the recieving end, the packets are then passed back up through the layers to the recieving device they are intended for.
What is the function of the application layer? What protocols operate at the application layer?
This is where network applications, such as web browsers or email programs, operate.
Transfer protocols (HTTP, HTTPS and FTP) and email protocols (SMTP and IMAP) operate at the application layer.
What is the function of the transport layer? What protocols operate at the transport layer?
This layer sets up the communication between the two hosts and they agree settings such as the size of packets.
Transmission protocols (TCP and UDP) operate at the transport layer.
What is the function of the internet layer? What protocols operate at the internet layer?
The internet layer addresses and packages data for transmission, and routes the packets across the network.
The addressing protocol (IP) operates at the internet layer.
What is the function of the link layer?
The link layer is where the network hardware such as the NIC (network interface layer) is located. OS device drivers also sit here. It attaches the MAC addresses of the sender and the recipient.
What is cyber security?
Cyber Security consists of the processes, practices and technologies designed to protect networks, computers, programs and data from attack, damage or unauthorised access.
What is social engineering?
The art of manipulating people so they give up confidential information.
What is blagging and how can it be prevented?
The act of inventing a scenario to engage a targeted victim in a way that would compel them to give away information or send money.
Recognising incorrect URLs or email addresses can help prevent this, or confirming the scenario you recieved with a trusted contact method, e.g. speaking to the bank via a trusted phone number and confirming whether they sent the email if you suspect blagging
What is phishing and how can it be prevented?
A technique of fraudulently obtaining information through email or SMS. The email may contain malware or might be used to steal a person’s money or identity.
Phishing emails are usually distinguished by spelling errors or unfamiliar email addresses/URLs.
What is shouldering and how can it be prevented?
Observing a person’s private information over their shoulder, e.g. watching them type their password.
Software prevents against shouldering by masking what is typed, showing an asterisk on the screen instead of the symbol that was entered.
What is pharming and how can it be prevented?
A cyber attack intended to redirect a user from a genuine website to a fake one, by hacking into the IP address of the webserver and changing it to that of the pharming site. HTTPS protocol can protect against this.
What is malicious code/malware and how can it be prevented?
Malware is an umbrella term that refers to a variety of forms of hostile or intrusive software.
What is a computer virus and how can it be prevented?
A virus is a self-replicating software that attaches itself to a file and replicates itself when executed without the user’s consent. They perform harmful activity on a device, such as using hard disk space or corrupting data. They are often spread through email attachments.
Anti-virus softwares hold a large database of known viruses that can detect if a program is similar to a known virus and warns the user.
What is a trojan and how can it be prevented?
A trojan is malware disguised as a piece of genuine software that contains malicious code hidden inside and only appears when the software is installed. They cannot self-replicate like viruses, but are often used in phishing attacks.
Confirming the details of the information you recieve before opening attachments can prevent malware corrupting your device, e.g. some websites may have incorrect branding
What is spyware and how can it be prevented?
Spyware is malware that collects information about activity on a computer system without the owner being aware. It is often used to track and store the user’s personal information, e.g. a keylogger monitors keys being pressed and uses this to steal bank login details.
Anti-spyware software can prevent this.
What are misconfigured access rights?
Access rights not being set up correctly, enabling someone to access what they do not have permission to see. Cyber criminals can use this to their advantage and take it as an opportunity to install malware or steal information.
What is unpatched/outdated software?
Patching is the process of updating software to fix a problem or add a new feature.
If a user uses outdated software no longer supported by its developers, then criminals would be able to discover security flaws and these would not recieve patches, allowing criminals to exploit this weakness.
What is penetration testing?
Penetration testing is the process of attempting to gain access to resources without knowledge of usernames, passwords and other normal means of access.
It is a way of testing systems to identify weaknesses in the system.
It uses the same techniques a hacker would try, but the aim is to identify weakness rather than steal data or damage the system.
Explain a malicious insider as a form of penetration testing (white box)
This simulates an attack from inside the system, where the attacker has knowledge and possibly basic credentials for the target system. They can use this to identify possible holes prior to starting the testing.
Explain an external attack as a form of penetration testing (black box)
This simulates an attack from outside the system where the attacker has no knowledge of any credentials for the target system and no understanding of how the system works. They would search for possible weaknesses or flaws using a trial and error approach.
What are 5 cyber security measures?
Biometric measures
Password systems
CAPTCHA
Tasks difficult for computers to form, but easy for humans, to distinguish between humans and computers and stop computers repeatedly trying to access a site
Email confirmations to confirm a user’s identity
Automatic software updates
Patching bugs before they can be exploited
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