paper 1 advanced information Flashcards
What is the purpose of a computer?
to take in data, process it, and then output it
What is hardware?
the physical components of the computer system, like the CPU, motherboard, monitor and printer
what is software?
the programs or applications that a computer system runs e.g. an operating system, a word processor or video game
What is a cpu?
A CPU (Central Processing Unit) is the “brain” of the computer system - it processes all of the data and instructions that make the system work
what are the three main parts of the CPU?
The control unit (CU), the arithmetic logic unit (ALU), and the cache.
What does the control unit do? what’s its main job?
It controls the flow of data inside and outside the CPU. It’s main job is to execute program instructions by following the fetch-decode-execute cycle.
What does the arithmetic logic unit (ALU) do?
All the calculations - it completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions using repeated addition and subtraction. It also performs logic operations such as AND, OR and NOT, and completes binary shifts.
It also contains the accumulator register.
What is the cache?
Very fast memory in the CPU - it stores regularly used data so that the CPU can access it quickly the next time it’s needed. When the CPU requests data. it checks the cache first to see if the data is there. if not, it will fetch it from RAM
What does the program counter (PC) do?
It holds the memory address of the next instruction for each cycle.
What does the memory address register (MAR) do?
it holds any memory address about to be used by the CPU. the address might point to data or a CPU instruction.
what does the memory data register (MDR) do?
it holds the actual data or instruction. this may have been fetched from memory, or be waiting to be written to memory
what does the accumulator do?
stores the results of the calculations in the ALU
What happens in the “fetch” part of the fetch-decode-execute cycle?
1) The memory address is copied from the program counter to the MAR
2) The instruction stored in the MAR address is copied to the MDR
3) the program counter is incremented (increased) to point to the address of the next instruction, ready for the next cycle
What happens in the “decode” part of the fetch-decode-execute cycle?
The instruction in the MDR is decoded by the CU. The CU may then prepare for the next step, e.g. by loading values into the MAR or MDR
what happens in the “execute” part of the fetch-decode-execute cycle?
The instruction is performed. This could be: load data from memory, write data to memory, do a calculation or logic operation (using the ALU), change the address in the PC, or halt the program.
name five hardware components of a typical desktop computer.
any five from:
- power supply
- case cooling fan
- CPU
- Heat sink
- Optical drive
- RAM
- hard disk drive/HDD
- graphics card/GPU
- Motherboard
What is RAM?
High speed, volatile memory - it’s where all data, files and programs are stored while they’re being used
what is virtual memory?
a part of secondary storage that is used as extra RAM
CPU performance depends on what three factors?
Clock speed, number of cores, and cache size
what is clock speed?
The number of instructions a single processor core can carry out per second (Hz). The higher the clock speed, the greater the number of instructions that can be carried out.
How does the number of cores affect the performance of a CPU?
Each core can process data independently of the rest, so the more cores a CPU has, the more instructions it can carry out at once, so the faster it can process a batch of data
what is primary storage?
the main memory areas that the CPU can access very quickly, such as CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile
what is secondary storage?
non-volatile memory that stores all data that’s not in use. Read/write speeds are much slower than primary storage.
How does a hard disk drive (HDD)/magnetic hard disk work?
A hard disk drive is made up of a stack of magnetised metal disks spinning at a rate of between 5400 and 15000 revolutions per minute. Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disks.
What are the advantages of Magnetic Hard Disks/HDDs?
- They are cheaper
- They are very high-capacity
- They have a longer read/write life than SSDs
What are the negatives of magnetic hard disks/HDDs?
They aren’t very durable and are easily broken because of their moving parts. They also aren’t very portable, and can not be carried around easily
What are solid state drives (SSDs)?
storage devices with no moving parts. Most of them use a type of flash memory. They are used for the same purpose as HDDs - for internal storage
What is flash memory?
a very common type of non-volatile memory that stores data in electrical circuits by trapping electrons
which have a faster read/write time - HDDs or SSDs?
SSDs
What are the advantages of SSDs?
- They are faster than HDDs
- They don’t need defragmenting
- They are more shock-proof than HDDs
- They are silent
- They have quite a high capacity
How much data can CDs hold?
around 700 MB
How much data can DVDs hold?
around 4.7GB
How much data can Blu-Ray disks hold?
around 25 GB
what are the three forms that optical disks come in?
read only, write-once, rewritable
What are some advantages of optical disks?
- They’re very cheap (per GB)
- They’re portable
- They won’t be damaged by water or shocks (although they are easily scratched)
Put these types of storage in order of their average read/write speed:
Magnetic tape, HDD, Memory card, Optical disk, SSD
Optical disk, Memory card, magnetic tape, HDD, SSD
Put these types of storage in order of their average cost per GB:
SSD, Optical disc, HDD, Memory Card, Magnetic tape
Magnetic tape, Optical disk, HDD, memory card, SSD
Put these types of storage in order of their average capacity:
HDD, SSD, Magnetic Tape, Optical disk, Memory card
Optical disk, memory card, SSD, HDD, Magnetic Tape
what does compression software do? where is it often used and why?
compression software reduces the size of files so they take up less disk space. it’s used lots on the internet to make files quicker to download.
what are standard file formats for compressed files?
.zip and .rar
what do you need to do to compressed files before you can use them?
extract them
what is a LAN?
A LAN (Local Area Network) is a network that covers a small geographical area, often located on a single sight.
who owns the hardware for a LAN?
the organization using it
Why use a LAN? (what are the positives?)
- sharing files is easier - network users can access the same files, work collaboratively on them and copy files between machines
- you can share the same hardware (like printers)
- the internet connection can be shared between every device connected to the LAN
- you can install and update software on all computers at once, rather than one-by-one
- you can communicate with all LAN users cheaply and easily, e.g. with instant messaging
- user accounts can be stored centrally, so users can log in from any device on the network
What is a WAN?
A WAN (Wide Area Network) is a network that connects LANs that are in different geographical locations. for example, a business with offices in three different countries would need a WAN for all their devices to connect together
Who owns the hardware for a WAN?
organisations hire infrastructure (e.g. communication lines) from telecommunications companies who own and manage the WAN. this is because a WAN is much more expensive to set up than a LAN.
Is the Internet a LAN or a WAN?
A WAN
Do most people have LANs or WANs in their homes?
Most people have LANs in their homes.
name 4 factors that can affect the performance of networks.
1 - Bandwidth (the amount of data that can be transferred in a given time)
2 - the amount of users (available bandwidth is shared between users of a network - too many users or heavy use may cause congestion and slow the network )
3 - mode of connection (wired connections are generally faster and more reliable than wireless)
4 - choice of hardware and network topology
What is a network interface controller (NIC)?
an internal piece of hardware that allows a device to connect to a network. they used to be on separate cards, but nowadays they’re built into the motherboard.
Do switches connect devices on a LAN or a WAN?
A LAN
Do switches transmit data in frames or packets?
frames
What address do switches use to transmit data?
a MAC address
Do routers transmit data within networks or between networks?
Between networks
Do routers direct data in frames or packets?
packets
Why are routers used in homes and offices?
to connect the LAN to the Internet
What are ethernet cables used for?
They are used to connect devices in a LAN
What are ‘twisted pair cables’?
pairs of wires that are twisted together to reduce interference.
Are ethernet cables twisted pair?
Yes
Are coaxial cables twisted pair?
No
Describe the structure of coaxial cables.
A single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference.
How do fibre optic cables transmit data?
as light
list three advantages and one disadvantage of fibre optic cables.
Advantages:
They are high performance
They don’t suffer interference
They can transmit over very large distances without loss of signal quality
Disadvantage:
They very expensive
What does a wireless connection use to transmit data?
Radio Waves
What is a WAP?
A Wireless Access Point - you need one to connect to a wireless network, and it is basically a switch that allows devices to connect wirelessly.
Advantages of a Client-server network:
- easier to keep track of files as they are stored centrally
- easier to perform back-ups
- easier to install and update software
- easier to manage network security (e.g. anti-malware software and user access levels)
- servers are very reliable and are always on
Disadvantages of a client-server network:
- expensive to set up and needs IT specialists to maintain the network and server
- server dependence - if the server goes down all clients lose access to their work
- the server may become overloaded if too many clients are accessing it all at once
Advantages of a peer-to-peer network:
- easy to maintain - you don’t need any expertise or expensive hardware
- no dependence on server - if one device fails the whole network isn’t lost
disadvantages of peer-to-peer networks:
- no centralized management - devices need their updates and security installed individually. Backups are also more complicated
- copying files between devices creates duplicate files, so it’s easy to lose track of what’s stored where and which files are up-to-date
- peer machines are less reliable and data may be lost if one fails
- machines are prone to slow down when other devices access them
describe a star network topology
all the devices are connected to a central switch or server that controls the network.
Pros of star topology:
- if a device fails or a cable is disconnected, the rest of the network is unaffected.
- it’s simple to add more devices to the network
- better performance than other setups - data goes straight to the central service so all devices can transmit data at once and there a few data collisions
Cons of star topology:
- in wired networks, every device needs a cable to connect to the central switch or server. This can be expensive, e.g. for an office building with 50 terminals
- if there is a problem with the switch/server, the whole network is affected
Is a mesh network centralised or decentralised?
decentralised
describe a mesh network.
all networking devices are either directly or indirectly connected to each other without the need for one central switch or server. Mesh networks work by sending data along the fastest route from one device to another.
What is the main advantage of a mesh network?
there is no single point where the network can fail - if one device fails then the data is sent along a different route to get to its target
what is the traditional disadvantage of mesh networks, and why is it becoming less of a problem?
they can be very expensive - you need a lot of wires to connect so many devices together. However, now that more people are using wireless technology, mesh networks are a more practical option.
what is the difference between a full mesh topology and a partial mesh topology?
in a full mesh topology, every device is connected to every other device, whereas in a partial mesh topology, not all devices are directly connected.
what address does communication on the same network use?
a MAC address
why do we have MAC addresses?
every device needs a unique identifier so it can be found on a network
How are MAC addresses assigned to a device?
MAC addresses are assigned to all network enabled devices by the manufacturer. They are unique to the device
can MAC addresses by changed?
no
how many bits do MAC addresses have? (how long is their binary number)
MAC addresses are 48 or 64 bit binary numbers (i.e. a long string of 48 or 64 0s and 1s)
what decimal system are MAC addresses converted into to make them easier to use?
hexidecimal
what are MAC addresses mainly used by?
the Ethernet protocol on LANs. LAN switches read the MAC addresses and use them to direct data to the right device
what address is used for communication between different networks?
IP address
when are IP addresses used?
when sending data between TCP/IP networks e.g. over the internet
are IP addresses linked to hardware?
no
are MAC addresses linked to hardware?
yes
when are IP addresses assigned?
they are assigned either manually (static) or automatically (dynamic) before the device can access the network
what are static IP addresses?
permanent addresses
what are static IP addresses used for?
they’re used to connect printers on a LAN and for hosting websites on the internet - companies don’t want the IP address of their website changing
what are dynamic IP addresses and when are they assigned?
dynamic IP addresses are assigned when a device logs on to a network, meaning that it may have a different address every time it connects.
which is more expensive - static IP addresses or dynamic IP addresses?
static IP addresses are more expensive - businesses pay big money for them. dynamic IP addresses are more cost-effective
do Internet Service Providers (ISPs) commonly use dynamic or static IP addresses?
dynamic - they are more cost effective and can be reused
how many bits is an IP address? (how many digits long is the binary number?)
either a 32-bit or a 128-bit binary number, depending on the version of IP you’re using
what are 128-bit IP addresses translated into?
eight hexadecimal numbers
what are 32-bit binary numbers converted into?
four denary (normal) numbers
what is packet switching used for?
packet switching is used by routers to direct data packets on the internet and other IP networks
what are the 6 steps of packet switching?
- the sending device splits the data into packets to be sent across the network. Each packet is given a packet number to show the order of the data
- each router reads the packet header and decides which way to send the packet next, according to the IP rules
- the way the data is sent next changes depending on network traffic so the packets can take different routes. If a router receives too many packets at once, it may prioritise some over others
- as the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order
- sometimes packets go missing in transit, so the receiving device checks periodically that all packets have been received. If it hasn’t received them within a certain time, it sends a timeout message back to the sending device
- if all the data is received and the checksums match, a receipt confirmation is sent to the sending devices
why is packet switching an efficient use of the network?
there are so many possible routes that data can take - packets can reach their receiving device even if there’s heavy traffic
what protocol is the internet based around?
TCP/IP
what is the world wide web?
a collection of websites that are hosted on web servers and accessed through the http protocol
what are URLs?
addresses used to access web servers and resources on them
what does a domain name server (DNS) do?
it translates a website’s domain name into it’s IP address - the internet has a network of domain name servers, meaning you don’t need to remember IP addresses to access websites - you can use domain names instead
what is hosting?
when a business uses its servers to store files of another organisation
what is the traditional use for hosting on the internet?
the hosting of website
what is a relatively recent use of internet hosting?
general storage of user files and also providing online software
what is the cloud?
general storage of user files and also providing online software - this is cloud computing, or simply ‘the cloud’. It acts like an extension of a traditional client-server network where user files are stored centrally on a network server
what virtual networks?
networks that are entirely software-based
how are virtual networks created?
by partitioning off some of a physical network’s bandwidth to form a separate network
can more than one virtual network exist on the same physical network?
yes
are virtual networks more or less efficient than standard physical networks?
more - they all share the same hardware
does each virtual network have its own security?
yes, including its own firewall. this means virtual networks can only be accessed by using certain software or login information - other people could be using the same physical network and not have access to the virtual network, or even know that it exists
what is a virtual private network (VPN)?
a type of virtual network that can be used to send data securely over a large network, like a WAN or the internet. e.g. a vpn can be used to send data securely between offices on different sites, or to set up a school intranet that all the students can access from home
what does a virtual LAN allow you to do?
split a LAN into several separate networks using the same hardware
what is a passive attack?
someone monitors data travelling on a network and intercepts any sensitive information they find. they use network-monitoring hardware and software such as packet sniffers.
are passive or active attacks harder to detect
passive attacks are harder to detect as the hacker is quietly listening
what is the best defence against passive attacks?
data encryption
what is an active attack?
when someone attacks a network with malware or other planned attacks
what is the main defence against active attacks?
a firewall
what is an insider attack?
Someone within an organisation exploits their network access to steal information
what is a brute force attack?
a type of active attack used to gain information by cracking passwords through trial and error. Brute force attacks use automated software to produce hundreds of likely password combination, e.g. combining real words with predictable number sequences. Hackers may try lots of passwords against one username or vice versa.
what helps to reduce the risk of a brute force attack?
simple measures like locking accounts after certain number of failed attempts and using strong passwords will reduce the risk of a brute force attack
what is a denial-of-service (DoS) attack?
where a hacker tries to stop users from accessing a part of a network or website. Most DoS attacks involve flooding the network with useless traffic, making the network extremely slow or completely inaccessible
what is malware?
malicious software that can harm devices
what are 6 typical actions of malware?
- deleting or modifying files
- scareware - e.g. it tells the user their computer is infected with loads of viruses to scare them into following malicious links or paying for problems to be fixed
- locking files - ransomware encrypts all the files on a computer. The user receives a message demanding a large sum of money be paid in exchange for a decryption key
- spyware - secretly monitors user actions, e.g. key presses, and sends info to the hacker
- rootkits alter permissions, giving malware and hackers administrator-level access to devices
- opening backdoors - holes in someone’s security which can be used for future attacks
what are three ways malware can access your device?
- viruses attach (by copying themselves) to certain files, e.g. .exe files and autorun scripts. Users spread them by copying infected files and activate them by opening infected files
- worms are like viruses but they self-replicate without any user help, meaning they can spread very quickly. they exploit weaknesses in network security.
- trojans are malware disguised as legitimate software. Unlike viruses and worms, trojans don’t replicate themselves - users install them not realising they have a hidden purpose
what is social engineering?
a way of gaining sensitive information or illegal access to networks by influencing people, usually the employees of large companies
describe a common form of social engineering that takes place over the telephone
someone rings up an employee of a company and pretends to be a network administrator or somebody else within the organisation. The social engineer gains the employee’s trust and persuades them to disclose confidential information - this might be personal (e.g. their login details) or sensitive company data
is phishing social engineering or malware?
social engineering
what is phishing?
phishing is when criminals send emails or texts to people claiming to be from a well-known business, e.g. a bank or an online retailer. The emails often contain links to spoof versions of the company’s website. They then request that the user update their personal information (e.g. password or bank account details). when the user inputs this data into the website they hand it all over to the criminals, who can then access their genuine account
which networks are vulnerable to SQL injection attacks?
networks which make use of databases
what is SQL?
Structured Query Language - it’s one of the main coding languages used to access information in databases
what are SQL injections?
pieces of SQL typed into a website’s input box which then reveal sensitive informatio
how do SQL injections work?
a website may allow you to view your account information, as long as you enter your password into an input box. If the website’s SQL code does not have strong enough input validation, then someone may be able to enter a piece of SQL code which allows them to access other people’s account information as well as their own.
what is a network policy?
a set of rules and procedures the organisation will follow to ensure their network is protected against attacks and unauthorised access
what are 5 things a good network policy will do?
- regularly test the network to find and fix security weaknesses and investigate any problems
- use passwords to prevent unauthorised people from accessing the network
- enforce user access levels to limit the number of people with access to sensitive information
- install anti-malware and firewall software to prevent and destroy malicious software attacks
- encrypt sensitive data
what is penetration testing?
penetration testing is when organisations employ specialists to simulate potential attacks on their network
what is penetration testing used for?
it’s used to identify possible weaknesses in a network’s security by trying to exploit them. the results of the pentest are then reported back
what are network forensics?
investigations undertaken to find the cause of attacks on a network.
what does an organisation need to have to conduct network forensics?
a system of capturing data packets as they enter their network
how do network forensics work?
an organisation captures all the data packets as they enter their network. after the network is attacked, these packets can be analysed to discover how the network was attacked and decide how to prevent further attacks
what makes a strong password?
a strong password should be many characters long, use a combination of letters, numbers and symbols, and be changed regularly
what do user access levels control?
which parts of the network different groups of users can access, e.g. business managers are likely to have a higher access level allowing them to access more sensitive data, like pay information
how do user access levels help to make a network more secure?
user access levels help limit the number of people with access to important data, so help prevent insider attacks on the network
what is anti-malware software designed to do?
to find and stop malware from damaging a network and the devices on it
what do antivirus programs do?
isolate and destroy computer viruses
what do companies use firewalls for?
to block unauthorised access. Firewalls examine all data entering and leaving the network and block any potential threats
what is encryption?
Encryption is when data is translated into a code which only someone with the correct key can access, meaning unauthorised users cannot read it
what is encrypted text called?
cipher text
what is non-encrypted data called?
plain text
what is encryption essential for?
sending data over a network securely
what does the computer measure when it samples a sound wave?
amplitude and frequency
what is metadata?
metadata means “data about data” and provides information about the data, e.g. file format, resolution, dimensions, colour depth, etc.
what are ethical issues about?
what would be considered right and wrong by society
what are legal issues about?
what’s actually right and wrong in the eyes of the law
what are cultural issues about?
how groups of people with particular beliefs, practices or languages may be affected, e.g. ethnic groups, religions, countries
what are environmental issues about?
how we impact the natural world
what are stakeholders?
individuals or groups of people who have an interest in or are affected by a particular scenario (e.g. the actions of a company or the development of a new technology)
what are some examples of stakeholders?
a company’s owners, its employees, the shop that sells the company’s product, customers, the company’s hardware suppliers and the local community
what could companies do with your personal information?
companies may make your personal information, photos, etc. available to other website users or organisations (who might use it to send you targeted adverts or spam emails). Companies can do lots with your information as long as they stay within the bounds of the privacy agreement
what is internet censorship?
when someone tries to control what other people can access on the internet. some countries’ governments use censorship to restrict access to certain information
what are two countries that use internet censorship, and in what way do they do it?
one of the strictest countries for censorship is China, where they restrict access to websites which are critical of the government. china also censors many major foreign websites, including facebook, twitter and youtube. in cuba, citizens can only access the internet from government-controlled access points
what are some ways that many countries (including the UK) use censorship?
they restrict access to pornography, gambling and other inappropriate websites in order to protect children
what is computer surveillance?
when someone monitors what other people are accessing on the internet
is it common for governments to use some form of surveillance?
yes
what is a way government intelligence agencies may use computer surveillance?
they may use packet sniffers and other software to monitor internet traffic, looking out for certain key words or phrases that may alert them to illegal activities, terrorism, etc.
how are internet service providers used for computer surveillance in some countries?
Internet service providers keep records of all websites visited by all its customers for a certain amount of time
what are two controversial topics/issues in computer science?
censorship and surveillance
what are two reasons people might support censorship or surveillance in some form?
to protect children or stop terrorism
how do smartphones make it easier for people’s work to intrude into other areas of life?
employees may be expected to carry a smartphone all the time, so that they can always be contact - the smartphone may beep each time that they get a work e-mail. This can be stressful for employees who feel they can never really switch off from work
how has technology increased peer pressure?
children feel pressure to own the latest device for fear of being bullied by their peers. Parents feel pressured into buying them
what are three ways new technology can impact our social well-being?
- increased peer pressure
- makes it easier for work to intrude into other areas of life
- face-to-face social interaction can be neglected
what is cyberbullying?
when somebody uses social media to deliberately harm someone else. this includes trying to intimidate or insult someone, or trying to humiliate or defame them (damage their reputation)
what is trolling?
when somebody tries to cause public arguments with others online. For example, the troll may take part in a political discussion online, but only to make comments which would frustrate the other members of the discussion
what are two reasons that people troll others?
for their own amusement or to gain attention
what are two things that may be a result of the anonymity the internet gives people?
cyberbullying and trolling - they say things online that they wouldn’t say face-to-face
why could sending sexually explicit messages or images to other people be dangerous?
the person receiving the images might not be trustworthy - social media allows them to forward someone else’s images to anyone they want. there are now laws that prevent this.
when you’re answering essay questions on these issues, what should you think about?
what groups are affected (stakeholders) and what issues (legal/ethical/cultural/environmental) it raises
the internet as made it easier for children to access inappropriate material, like pornography, drugs and gambling. What can parents and schools use to try to stop children seeing it?
parental-control software
what is the sharing economy?
the name given to services which use new technology to let people make money from things they already own - e.g. Airbnb uses the internet to let you rent out a room in your house to tourists
what is an advantage of the sharing economy?
it makes things cheaper
what are some disadvantages of the sharing economy?
they draw customers away from original businesses, and they may be more risky for sharers and customers
what is the digital divide created by?
the fact that some people have greater access to technology than others
what are some examples of how people are advantaged by having access to the internet?
people can use the internet to apply for jobs or university courses, access a range of services from banking to retail, and keep in touch with friends. people who have a limited access to the internet are therefore at a heavy disadvantage
what are 3 causes of the digital divide?
- some people don’t have enough money to buy new devices like smartphones and laptops, which can be very expensive
- urban areas are likely to have greater network coverage than rural areas
- some people don’t know how to use the internet and other new technologies, and so are shut out of the opportunities they offer. this is a problem for many older people who haven’t grown up with computers and so have little experience with them
what is the global divide created by?
the fact that the level of access to technology is different in different countries. people in richer countries tend to have greater access to technology than people in poorer countries. the internet and other technologies have created lots of opportunities for the people with access to them, so this has increased the inequality between poorer and richer countries
what is One Laptop Per Child?
a charity which provides laptops to children in Africa, Central Asia and South America. it is one of the several projects that have been set up to combat the digital and global divides
what are plastics used for in devices, and where do they come from?
they are used for casting and other parts, and they come from crude oil
what precious metals do devices contain?
any three from: gold, silver, copper, mercury, palladium, platinum and indium
how is making devices bad for the environment?
extracting the raw materials for electronic devices uses lots of energy, creates pollution and depletes scarce natural resources
how is most electricity made, and how is this relevant to computer science?
most electricity is made using non-renewable resources like coal oil and gas - the billions of devices in the world today are consuming lots of energy in the form of electricity. Extracting the resources to make electricity and producing electricity in power stations causes lots of pollution including greenhouse gasses
all computers generate heat. how does this increase the negative environmental effects from computers?
all computers generate heat and therefore require cooling. the powerful servers used by businesses and the internet are a particular problem. they’re very power hungry and require special air-conditioned rooms to keep them cool. this means using even more energy and more pollution
how do devices waste a lot of energy?
servers normally only use a small proportion of their processing power. people often leave their desktops, laptops and smartphones idle. this means that these devices are using a lot of energy without actually doing anything
what are three ways to reduce the amount of energy wasted by devices?
- virtual servers are software-based servers rather than real machines. multiple virtual servers can run on one physical server, so the physical server can run at full capacity
- most modern devices include sleep and hibernation modes to reduce their power consumption when they are idle
- don’t leave electronic devices (TVs, laptops, etc.) on standby
what do we create when we throw away devices?
lots of E-waste
how much e-waste does the world create each year?
20-50 million tonnes
how are device manufacturers and retailers part of the problem of E-waste?
they provide short warranties (e.g. 1 year), use marketing to convince people to upgrade and have pricing policies that make it cheaper to replace than to repair
what was the Waste Electricity and Electrical Equipment (WEEE) directive created for?
to tackle the e-waste problem
how does the WEEE plan to tackle the e-waste problem?
it has rules for disposing of e-waste safely, to promote reuse (e.g. refurbishing broken devices to use again) and recycling (e.g. extracting the devices’ precious metals)
why is a lot of e-waste sent to certain african and asian countries?
to cut costs, and regulations are less strict there
where does most of the e-waste end up in britain?
landfill - it can be a hazard as toxic chemicals can leak into the ground water and harm wildlife
what are 2 positive environmental effects of devices?
they let us communicate without having to travel long distances in pollution-spouting vehicles, and reduce our need for paper
what are two reasons why someone might give their personal details to a website?
many websites (e.g. social media, banking and retail) require users to provide personal information in order to set up and account, e.g. date of birth and address
social media websites actively encourage users to upload personal files to their servers
name two problems with many online companies’ privacy agreements
- very few people actually read the privacy agreements, so are unaware of what they’re agreeing to
- users have no choice to agree if they want to use the website or software at all
what can you do to make the information you share online more private?
change you privacy settings on social media sites.
give three examples of how technology and the internet have shaped our culture
- selfies - they’ve become really popular due to being able to take them and share them more easily, but they could be seen as a sign that social media is gradually making people more attention-seeking and self-obsessed
- viral videos - a big aim for companies, politicians, celebrities and charities in their promotional campaigns
- social media and blogging websites - give a voice to groups of people who might have been ignored my mainstream media
what are 2 potential problems with privacy settings on social media?
- websites often have fairly relaxed privacy settings by default
- they can have privacy settings that are hard to find and hard to understand
what is a protocol?
a set of rules for how devices communicate and how data is transmitted across a network
what information do protocols cover?
how communication between two devices should start and end, how the data should be organised, and what the devices should do if data goes missing
what are the three components of a data packet?
- header - contains control information - like the envelope of a letter - includes packet’s destination address (where it’s going), the source address (where it’s come from) and the packet number
- payload - the letter inside the envelope - the thing the person is likely to read, and the reason it was sent in the first place. might be part of an email, document, web page of streamed video.
- likely to include a checksum number - a form of validation used to check that the payload data hasn’t been corrupted during transit. the sending and receiving devices both calculate a checksum value by performing a function on the payload data. if the values match then the data has been received correctlly
what does the TCP/IP protocol do?
dictate how data is sent between networks
what two protocols is the TCP/IP protocol made up of?
Transmission control protocol (TCP) and Internet Protocol (IP)
what does the transmission control protocol (TCP) do?
set the rules for how devices connect on the network. It’s in charge of splitting the data into packets and reassembling the packets back into the original data once they reach the receiving device. It’s also responsible for checking the data is correctly sent and delivered
what is the internet protocol (IP) responsible for?
packet switching
what is the Hyper Text Transfer Protocol (HTTP) used for?
used by web browsers to access websites and communicate with web servers
what is the HTTPS protocol?
a more secure version of HTTP. encrypts all information sent and received
what is the file transfer protocol (FTP) used for?
used to access, edit and move files between devices on a network e.g. to access the files on a server from a client computer
what does POP3 stand for?
Post Office Protocol - version 3
what is POP3 used for?
used to retrieve emails from a server. The server holds the email until you download it at which point it is deleted from the server
what does IMAP stand for?
Internet Message Access Protocol
what is IMAP used for?
used to retrieve emails from a server. The server holds the email until you delete it - you only download a copy. Used by most web-based email clients
what does SMTP stand for?
simple mail transfer protocol
what is SMTP used for?
used to send emails. Also used to transfer emails between servers
what is a layer?
a group of protocols which have similar functions
what is the name of layer 4?
application layer
what does layer 4 do?
turns data into websites and other applications and vice versa
what is the name of layer 3?
transport layer
what does layer 3 do?
controls data flow - e.g. splitting data into packets and checking packets are correctly sent and delivered
what is layer 2 called?
network layer
what does layer 2 do?
makes connections between networks, directs data packets and handles traffic. used by routers
what is layer 1 called?
data link layer
what does layer 1 do?
Passes data over the physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware
what protocols work in layer 4 (the application layer)?
HTTP, FTP, SMTP
what protocols work in layer 3 (the transport layer)
TCP (transmission control protocol)
what protocols work in layer 2 (the network layer)?
IP
what protocols work in layer 1 (the data link layer)?
ethernet
what are the advantages of using layers?
- it breaks network communication into manageable pieces. This helps developers to concentrate on only one area of the network without having to worry about others
- as layers are self-contained, they can be changed without the other layers being affected
- having set rules for each layer forces companies to make compatible, universal hardware and software, so different brands will work with each other and in basically the same way
what is the first principle of the data protection act?
data must only be used in a fair and lawful way
what is the second principle of the data protection act?
data must only be used for the specified purpose
what is the third principle of the data protection act?
data should be adequate, relevant and not excessive for the specified use
what is the fourth principle of the data protection act?
data must be accurate and kept up-to-date
what is the fifth principle of the data protection act?
data should not be kept longer than necessary
what is the sixth principle of the data protection act?
the rights of the data subject must be observed
what is the seventh principle of the data protection act?
data should be kept safe and secure
what is the eighth principle of the data protection act?
data should not be transferred abroad without adequate protection
what does the data protection act 1998 do?
it gives rights to data subjects
what is a data subject?
a person whose personal data is stored on computer systems
what does the data protection act mean for organisations?
- before collecting personal data an organisation must register with the government, saying what data they’ll collect and how they’ll use it
- the act gives data subjects the right to see the personal data an organisation holds about them
- there are some exceptions to this, e.g. organisations don’t have to disclose the data they hold if it could affect national security, tax assessment, or the outcome of a court case
- if a data subject feels an organisations use of their data has caused them distress, they may be entitled to compensation
what does the Freedom of Information Act 2000 allow?
public access to data - it allows members of the public to access information held by a public organisation about that organisation’s activities. The Act covers information stored in computer data files (including audio and video files), emails, and printed documents
what are some exceptions to the Freedom of Information Act 2000?
an organisation can withhold requested information if it is intended for future publication, or if disclosing it could affect national security or cause people harm
what does the computer misuse act 1990 prevent?
illegal access to files - it was introduced to stop hacking and cyber crime
what three new offences did the Computer Misuse Act 1990 introduce?
- Gaining unauthorised access to a private network or device, e.g. through hacking
- gaining unauthorised access to a network or device in order to commit a crime like stealing data or destroying the network
- unauthorised modification of computer material - e.g. deleting or changing files. The Act also makes it illegal to make, supply or obtain malware
what does the Copyright, Designs and Patents Act 1988 protect?
innovation - it was introduced to protect intellectual property - anything that someone has created
what does the Copyright, Designs and Patents Act 1988 make illegal?
it makes it illegal to share copyrighted files without the copyright holder’s permission, use unlicensed software of plagiarise somebody else’s work. Copyright holders can make money by granting permission to use the material for a fee
why has the internet made it harder to protect copyrighted content?
because of the ease of file sharing. It’s also difficult to enforce copyright if content is held on servers in countries with more relaxed copyright laws
what do Creative Commons licenses allow?
legal file sharing - they allow you to legally share media and software online without having to ask for permission first. Intellectual property owners use creative commons licences when they want other people to share of build upon their work
what are the four main types of creative commons licence?
- Attribution - work can be shared, copied or modified, but the copyright holder has to be credited
- Share-alike - modified works can only be distributed with the same license terms as the original
- Non-commercial - nobody can use the copyrighted work for profit
- No derivative works - the work can be copied and distributed, but can’t be modified or built upon
can you combine CC licences?
yes
what does it mean for works to be in the public domain?
they don’t have any copyright attached to them, meaning you can copy them and share them as you wish.
when does UK copyright expire?
70 years after the creators death, at which point their creation enters the public domain - Shakespeare’s plays, Beethoven’s symphonies and da Vinci’s paintings are all no in the public domain
what are alphanumeric characters used for?
they are used to make words and strings. They include uppercase and lowercase letters, the digits 1-9, and symbols like ? + and £
what are character sets?
collections of characters that a computer recognises from their binary representation
what is ASCII?
- ASCII is the most commonly-used character set in the English-speaking world. Each ASCII character is given a 7-bit binary code - this means it can represent a total of 128 different characters, including all the letters in the English alphabet, numbers, symbols and commands
- An extra bit (0) is added to the start of the binary code for each ASCII character. This means each ASCII character fits nicely into 1 byte
what is extended ASCII?
a character set which gives each character an 8-bit binary code, allowing for 256 characters to be represented. The first 128 characters are in exactly the same order as the ASCII characters.
Extended ASCII is particularly useful for many European languages like French and German which include accents on some of the vowels
what is unicode?
- unicode is a character set that comes in several different forms and tries to cover every possible character that might be written. In its most common forms it uses 16-bit and 32-bit binary codes
- Unicode is that covers all major languages , even those that use a completely different alphabet like Greek, Russian and Chinese
what are the 2 types of images?
bitmap and vector
what are bitmap images mainly used for?
photos
how are bitmap images stored as binary?
Bitmap images are made up of lots of tiny dots, called pixels. The colour of each pixel is represented by a binary code. The number of colours available in an image is related to the number of bits the code has
what is colour depth?
the number of bits used for each pixel
what is the formula to work out how many colours can be made in an image?
total number of colours = 2^n (where n = number of bits per pixel, or bpp)
what colour depth do most devices use?
a 24-bit colour depth, with 8 bits used to indicate the levels of red, green and blue needed for each pixel. It is estimated that the human eye can see around 10 million different colours, so a 24-bit colour depth should cover every colour that you could possibly see
what is the resolution of an image? What is resolution normally measured in?
the density of pixels in an image, i.e. how many pixels are within a certain area. It’s normally measured in dots per inch (dpi)
what does increasing the resolution or the colour depth of an image mean?
that there are more bits in the image. This improves the image quality but also increases the file size
what is metadata? (images)
the information stored in an image file which helps the computer recreate the image on the screen from the binary data in each pixel. It usually includes the image’s file format, height, width, colour depth and resolution. It can also include extra information, like the time and date that the image was created or last edited. Without metadata, devices would not be able to display the image on screen as intended
what are the steps to sampling sound and storing it digitally?
- sound is recorded by a microphone as an analogue signal. Analogue signals are pieces of continually changing data
- analogue signals need to be converted into digital data so that computers can read and store sound files. This is done by analogue to digital converters, which are found in most modern recording devices
- the process of converting analogue to digital is called sampling: to convert the analogue recording to digital data, we sample the amplitude of the wave at regular intervals. The amplitude can only take certain values depending on the bit rate.
- once the device has sampled the recording, it creates the curve digitally
how is a digital sound wave similar/different to an analogue sound wave?
- the digital data is about the same shape as the analogue wave, but it’s not continuous. It’s lost a lot of data - the peak of the analogue wave is much flatter in the digital data
how can digital sound data be improved?
by taking samples more regularly - most music isn’t sampled every second but every millisecond
what are sampling intervals?
the gaps between each of the points where the analogue recording is sampled. E.g. the audio file might be sample every 5 milliseconds (ms), in which case the sampling interval would be 5 ms
what is sampling frequency (or sample rate)? What is it usually measured in?
how many samples you take in a second - it’s usually measured in kilohertz (kHz). E.g. a common sampling frequency is 44,100 samples per second (44.1 kHz)
what is sample size?
the number of bits available for each sample (like colour depth but for sound samples)
what is bit rate?
the number of bits used per second of audio
what is the formula for bit rate?
bit rate = sampling frequency x sample size
what is bit rate usually measured in?
kilobits per second (kbit/s)
what would happen if you increased the sampling frequency?
increasing the sampling frequency means the analogue recording is sampled more often. The sampled sound will therefore be better quality and will more closely match the original recording.
what will happen if you increase the sample size of a sound recording?
increasing the sample size means the digital file picks up quieter sounds, even if they’re happening at the same time as louder ones. This will also result in a sampled sound that is closer the the quality of the original recording.
what is a negative of increasing the sampling frequency and sample size?
a larger file size
what is data compression?
making files smaller, while trying to make the compressed file as true to the original as possible
what are the benefits of compression?
- smaller files take up less storage space on a device
- streaming and downloading files from the internet is quicker as they take up less bandwidth
- it allows web pages to load more quickly in web browsers
- email services normally have restrictions on the size of the attachment you can send - compressing the file allows you to send to same content with a much smaller file size
how does lossy compression work?
by permanently removing data from the file - this limits the number of bits the file needs and so reduces its size
how does lossless compression work?
lossless compression makes the file smaller by temporarily removing data to store the file and then restores it to its original state when it’s opened
what are the pros of lossy compression?
- greatly reduces file size, meaning more files can be stored
- lossy files take up less bandwidth so can be downloaded and streamed more quickly
- commonly used - lots of software can read lossy files
what are the cons of lossy compression?
- lossy compression loses data - the file can’t be turned back into the original
- lossy compression can’t be used on text or software files as these files need to retain all the information of the original
- lossy files are worse quality than the original, but this loss in quality is normally unnoticeable
what are the pros of lossless compression?
- data is only removed temporarily so there is no reduction in quality - the compressed file should look or sound like the original
- lossless files can be decompressed - turned back into the original
- lossless compression can be used on text and software files
what is the con of lossless compression?
there’s only a slight reduction in file size, so lossless files still take up quite a bit of space on your device. E.g. a lossless song may have a file size of around 30 MB, while the same song with lossy compression may be 5MB
give 3 examples of lossy file types
- MP3 (audio)
- AAC (audio)
- JPEG (image)
give 3 examples of lossless compression file types
- FLAC (audio)
- TIFF (image)
- PNG (image)
what is the purpose of the CPU?
to process data by fetching, decoding, and executing instructions
what is a register?
a small piece of memory that is volatile. It is directly accessed by the CPU and will store instructions, addresses or data
what is the purpose of the Memory Address Register?
to store the address of the next instruction/data to be accessed
what is the purpose of the Memory Data Register?
to store the data to be brought from/sent to main memory
what is the purpose of the program counter?
to store the address of the next instruction
what is the purpose of the accumulator?
to store the value currently being worked on/result of the last calculation
name 4 registers in the CPU
- memory address register
- memory data register
- program counter
- accumulator
what are the effects of using a processor with a faster clock speed?
more instructions carried out per second and so instructions are executed more quickly
what are the effects of using a processor with more cores?
more instructions carried out simultaneously; the processor can process more instructions at the same time, which allows batches of instructions to be executed more quickly; allows for more programs that are designed to be run on multiple cores to be run faster.
What are the effects of using a processor with a bigger cache?
More space for frequently used instructions/data, more storage for faster access than from RAM.
give 7 examples of embedded systems
- Dishwasher
- MP3 player
- Washing machine
- Mobile phone
- Manufacturing equipment
- Sat Nav
- Car collision detection
what is the function of the ALU?
used to perform arithmetic calculations (e.g. +, -, *), used to perform logical operations (e.g. , =, !=)
what does ALU stand for?
Arithmetic and logic unit
what is the function of the control unit?
Transmits timing signals to manage and regulate actions such as reading and writing data, the input and output of data
what is the function of the cache?
Stores frequently used instructions and data, built onto the CPU, provides faster access than RAM, allows instructions and data to be loaded into the CPU more quickly.
What are three items that are stored in RAM?
- Programs currently in use.
- Data currently in use.
- OS currently in use
What is the main difference between RAM and ROM?
ROM is non-volatile and RAM is volatile
What is virtual memory?
- It is simulated memory that is written to a file on the hard drive
- memory that appears to exist as RAM but is in secondary storage.
Why is virtual memory needed?
When you need to run more/larger applications on the computer than its physical memory (RAM) can support.
It lets more memory be used than there is in the system.
How is virtual memory implemented?
- Operating system will set up virtual memory using the virtual memory manager (VMM).
- VMM creates a file on the hard disk large enough for the extra memory needed.
- OS can then address memory as if it were real memory stored in RAM.
- Maps memory addresses used by a program into physical addresses in computer memory.
- Swapping or paging is a process used by the operating system to move data between RAM and virtual memory.
- Operating system moves data when some processes are not needed immediately out of the RAM to store them in virtual memory (on the hard disk).
- Copies the data back into RAM when the process is needed again.
- Transfer between the two being made automatically as required
What does solid state media mean?
Storage media with no moving parts
Refers to removable storage with no moving parts
Device that uses flash memory
name three storage devices that use flash memory
USB drives
Memory cards (such as in a camera)
Solid-state drives
what are the advantages of using flash memory?
- Flash is durable will not break if dropped or exposed to heat.
- Very reliable as no moving parts.
- Very compact but can store lot of data in a small space.
- Very fast access time compared to a hard disk or a DVD.
- Low cost and reliable.
- Light weight so easily portable.
what are the disadvantages of using flash memory?
- Can get lost easily.
- Can wear out over a long time period.
- More expensive than CD or DVD.
- The metal part that is inserted into the USB port can become bent or damaged.
Why is secondary storage needed on a computer?
Used to back up data stored in main memory/primary storage.
Stores programs/data and other files that would otherwise be lost when the power is switched off/RAM is volatile/cannot store data permanently.
Need for larger storage capacity.
What are three advantages for using secondary storage?
Memory is non-volatile.
Data is not lost when the computer is switched off.
Stores larger amount of data.
name 8 external storage devices
CDs Memory card DVD Blu-ray disc Flash drive USB memory stick (External) hard disk drive (External) solid state drive
name 2 internal storage devices
Hard disk drive (HDD)
Solid state drive (SSD)
name 3 types of secondary storage device
- optical
- magnetic
- solid state
what are the advantages of optical storage devices?
Inexpensive/reliable/robust/relatively large capacity
what are the advantages of magnetic storage devices?
Store large capacity/commonly used making it possible to share compatibility/can be used to store operating system and other files and programs/reliable/cost-effective
what are the advantages of solid state storage devices?
Flexible/Inexpensive/faster access to data/Can be used for portable devices/generally smaller in size/robust/easy to use/no setup requirements.
Which type of secondary storage is most suitable for distributing a movie? What is the most suitable storage device for distributing a movie?
the most suitable type is optical, and the most suitable device is DVD/Blu Ray
what is the most suitable secondary storage device for distributing music tracks? Why?
CD:
- Cheap to produce.
- Easily portable.
- Enough capacity for the music tracks.
- Can be read by other devices.
- Read only/can’t be over written
What are the disadvantages of using magnetic tape to store data?
Slow to write to and read from memory.
All data has to be read before reading the data you want.
Data could be corrupted if close enough to a magnetic field.
Additional equipment needed to read data from tape.
How many bytes are in 3MB of data?
3 000 000 (3 million)
Which factors should be considered when deciding on how data is stored?
Capacity Speed Portability Durability Reliability Cost
What is the highest value that can be represented by a nibble?
15
How many megabytes are there in 3 gigabytes?
3072 Megabytes or 3000Mb is acceptable.
An overflow error can occur when adding two 8-bit binary values. What is an overflow error?
There is an extra carry/bit
The result exceeds 8 bits
The result is more than 255/11111111
Why do people use hexadecimal values to represent numbers stored in computers?
Hexadecimal values are shorter than binary. Hexadecimal values are easier to work with than binary. Hexadecimal values are easily converted. Hexadecimal values are less susceptible to errors.
Why is a check digit used?
Used to ensure a range of numbers have been entered correctly. Detects errors on identification numbers.
What is meant by the term character set?
The range of numbers, letters and symbols that can be represented by a computer, each character having its own binary value
What does ASCII stand for?
American Standard Code for Information Interchange.
how many bits does standard ASCII use?
7
Why would Unicode be used?
To use other special characters found in different languages.
how many bits does Unicode use?
Normally 16 bits (2 bytes) but up to 32 bits (4 bytes) used to encode set characters
What is a Pixel?
the smallest element that makes up an image
Why is metadata included in a file?
A computer needs to know the size of the image in terms of height, width and colour depth in bits per pixel (bpp) …this allows the computer to recreate the image from binary.
What is meant by a bit rate?
What is meant by a bit rate?
How can sound be sampled and stored in digital form?
Sound is continuously changing values (in analogue). The frequency is read at set intervals. Set values are saved and replayed. The sample rate affects the quality of the sound/ a high sample rate (or sampling sound at shorter intervals) improves the quality of the sound.
what are the advantages of compressing files?
Reduce download size. Reduce download time when transferring a file. Reduce storage requirement.
What is meant by lossy compression?
Removing data from a file (commonly images and sound) to reduce its size. Data is lost when file is uncompressed which means that the image cannot be restored to its original condition.
What is meant by lossless compression?
Compressing a file without losing any information. No bits are lost after the image has been restored. All data is restored after file has been uncompressed.
What is the purpose of a computer?
to take in data, process it, and then output it
What is a cpu?
A CPU (Central Processing Unit) is the “brain” of the computer system - it processes all of the data and instructions that make the system work
what are the three main parts of the CPU?
The control unit (CU), the arithmetic logic unit (ALU), and the cache.
What does the control unit do? what’s its main job?
It controls the flow of data inside and outside the CPU. It’s main job is to execute program instructions by following the fetch-decode-execute cycle.
What does the arithmetic logic unit (ALU) do?
All the calculations - it completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions using repeated addition and subtraction. It also performs logic operations such as AND, OR and NOT, and completes binary shifts.
It also contains the accumulator register.
What is the cache?
Very fast memory in the CPU - it stores regularly used data so that the CPU can access it quickly the next time it’s needed. When the CPU requests data. it checks the cache first to see if the data is there. if not, it will fetch it from RAM
What does the program counter (PC) do?
It holds the memory address of the instruction for each cycle.
What does the memory address register (MAR) do?
it holds any memory address about to be used by the CPU. the address might point to data or a CPU instruction.
what does the memory data register (MDR) do?
it holds the actual data or instruction. this may have been fetched from memory, or be waiting to be written to memory
what does the accumulator do?
stores the results of the calculations in the ALU
What happens in the “fetch” part of the fetch-decode-execute cycle?
1) The memory address is copied from the program counter to the MAR
2) The instruction stored in the MAR address is copied to the MDR
3) the program counter is incremented (increased) to point to the address of the next instruction, ready for the next cycle
What happens in the “decode” part of the fetch-decode-execute cycle?
The instruction in the MDR is decoded by the CU. The CU may then prepare for the next step, e.g. by loading values into the MAR or MDR
what happens in the “execute” part of the fetch-decode-execute cycle?
The instruction is performed. This could be: load data from memory, write data to memory, do a calculation or logic operation (using the ALU), change the address in the PC, or halt the program.
What is RAM?
High speed, volatile memory - it’s where all data, files and programs are stored while they’re being used
what is primary storage?
the main memory areas that the CPU can access very quickly, such as CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile
what is secondary storage?
non-volatile memory that stores all data that’s not in use. Read/write speeds are much slower than primary storage.
How does a hard disk drive (HDD)/magnetic hard disk work?
A hard disk drive is made up of a stack of magnetised metal disks spinning at a rate of between 5400 and 15000 revolutions per minute. Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disks.
What are the advantages of Magnetic Hard Disks/HDDs?
- They are cheaper
- They are very high-capacity
- They have a longer read/write life than SSDs
What are the negatives of magnetic hard disks/HDDs?
They aren’t very durable and are easily broken because of their moving parts. They also aren’t very portable, and can not be carried around easily
What are solid state drives (SSDs)?
storage devices with no moving parts. Most of them use a type of flash memory. They are used for the same purpose as HDDs - for internal storage
What is flash memory?
a very common type of non-volatile memory that stores data in electrical circuits by trapping electrons
which have a faster read/write time - HDDs or SSDs?
SSDs
What are the advantages of SSDs?
- They are faster than HDDs
- They don’t need defragmenting
- They are more shock-proof than HDDs
- They are silent
- They have quite a high capacity
How much data can CDs hold?
around 700 MB
How much data can DVDs hold?
around 4.7GB
How much data can Blu-Ray disks hold?
around 25 GB
what are the three forms that optical disks come in?
read only, write-once, rewritable
What are some advantages of optical disks?
- They’re very cheap (per GB)
- They’re portable
- They won’t be damaged by water or shocks (although they are easily scratched)
Put these types of storage in order of their average read/write speed:
Magnetic tape, HDD, Memory card, Optical disk, SSD
Optical disk, Memory card, magnetic tape, HDD, SSD
Put these types of storage in order of their average cost per GB:
SSD, Optical disc, HDD, Memory Card, Magnetic tape
Magnetic tape, Optical disk, HDD, memory card, SSD
Put these types of storage in order of their average capacity:
HDD, SSD, Magnetic Tape, Optical disk, Memory card
Optical disk, memory card, SSD, HDD, Magnetic Tape
what does compression software do? where is it often used and why?
compression software reduces the size of files so they take up less disk space. it’s used loads on the internet to make files quicker to download.
what are standard file formats for compressed files?
.zip and .rar
what do you need to do to compressed files before you can use them?
extract them
who owns the hardware for a LAN?
the organization using it
Is the Internet a LAN or a WAN?
A WAN
name 4 factors that can affect the performance of networks.
1 - Bandwidth (the amount of data that can be transferred in a given time)
2 - the amount of users (available bandwidth is shared between users of a network - too many users or heavy use may cause congestion and slow the network )
3 - mode of connection (wired connections are generally faster and more reliable than wireless)
4 - choice of hardware and network topology
What is a network interface controller (NIC)?
an internal piece of hardware that allows a device to connect to a network. they used to be on separate cards, but nowadays they’re built into the motherboard.
Do switches connect devices on a LAN or a WAN?
A LAN
Why are routers used in homes and offices?
to connect the LAN to the Internet
What are ethernet cables used for?
They are used to connect devices in a LAN
Are ethernet cables twisted pair?
Yes
What does a wireless connection use to transmit data?
Radio Waves
What is a WAP?
A Wireless Access Point - you need one to connect to a wireless network, and it is basically a switch that allows devices to connect wirelessly.
what address does communication on the same network use?
a MAC address
why do we have MAC addresses?
every device needs a unique identifier so it can be found on a network
How are MAC addresses assigned to a device?
MAC addresses are assigned to all network enabled devices by the manufacturer. They are unique to the device
can MAC addresses by changed?
no
how many bits do MAC addresses have? (how long is their binary number)
MAC addresses are 48 or 64 bit binary numbers (i.e. a long string of 48 or 64 0s and 1s)
what decimal system are MAC addresses converted into to make them easier to use?
hexidecimal
what are MAC addresses mainly used by?
the Ethernet protocol on LANs. LAN switches read the MAC addresses and use them to direct data to the right device
what address is used for communication between different networks?
IP address
when are IP addresses used?
when sending data between TCP/IP networks e.g. over the internet
are IP addresses linked to hardware?
no
are MAC addresses linked to hardware?
yes
when are IP addresses assigned?
they are assigned either manually (static) or automatically (dynamic) before the device can access the network
what are static IP addresses?
permanent addresses
what are static IP addresses used for?
they’re used to connect printers on a LAN and for hosting websites on the internet - companies don’t want the IP address of their website changing
what are dynamic IP addresses and when are they assigned?
dynamic IP addresses are assigned when a device logs on to a network, meaning that it may have a different address every time it connects.
which is more expensive - static IP addresses or dynamic IP addresses?
static IP addresses are more expensive - businesses pay big money for them. dynamic IP addresses are more cost-effective
do Internet Service Providers (ISPs) commonly use dynamic or static IP addresses?
dynamic - they are more cost effective and can be reused
how many bits is an IP address? (how many digits long is the binary number?)
either a 32-bit or a 128-bit binary number, depending on the version of IP you’re using
what is packet switching used for?
packet switching is used by routers to direct data packets on the internet and other IP networks
what are the 6 steps of packet switching?
- the sending device splits the data into packets to be sent across the network. Each packet is given a packet number to show the order of the data
- each router reads the packet header and decides which way to send the packet next, according to the IP rules
- the way the data is sent next changes depending on network traffic so the packets can take different routes. If a router receives too many packets at once, it may prioritise some over others
- as the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order
- sometimes packets go missing in transit, so the receiving device checks periodically that all packets have been received. If it hasn’t received them within a certain time, it sends a timeout message back to the sending device
- if all the data is received and the checksums match, a receipt confirmation is sent to the sending devices
why is packet switching an efficient use of the network?
there are so many possible routes that data can take - packets can reach their receiving device even if there’s heavy traffic
what protocol is the internet based around?
TCP/IP
what is the world wide web?
a collection of websites that are hosted on web servers and accessed through the http protocol
what is the best defence against passive attacks?
data encryption
what is the main defence against active attacks?
a firewall
what helps to reduce the risk of a brute force attack?
simple measures like locking accounts after certain number of failed attempts and using strong passwords will reduce the risk of a brute force attack
what is a network policy?
a set of rules and procedures the organisation will follow to ensure their network is protected against attacks and unauthorised access
what is penetration testing?
penetration testing is when organisations employ specialists to simulate potential attacks on their network
what is penetration testing used for?
it’s used to identify possible weaknesses in a network’s security by trying to exploit them. the results of the pentest are then reported back
what are network forensics?
investigations undertaken to find the cause of attacks on a network.
what makes a strong password?
a strong password should be many characters long, use a combination of letters, numbers and symbols, and be changed regularly
what do user access levels control?
which parts of the network different groups of users can access, e.g. business managers are likely to have a higher access level allowing them to access more sensitive data, like pay information
how do user access levels help to make a network more secure?
user access levels help limit the number of people with access to important data, so help prevent insider attacks on the network
what is anti-malware software designed to do?
to find and stop malware from damaging a network and the devices on it
what do antivirus programs do?
isolate and destroy computer viruses
what do companies use firewalls for?
to block unauthorised access. Firewalls examine all data entering and leaving the network and block any potential threats
what is encryption?
Encryption is when data is translated into a code which only someone with the correct key can access, meaning unauthorised users cannot read it
what is encrypted text called?
cipher text
what is non-encrypted data called?
plain text
what is encryption essential for?
sending data over a network securely
what does the computer measure when it samples a sound wave?
amplitude and frequency
what is metadata?
metadata means “data about data” and provides information about the data, e.g. file format, resolution, dimensions, colour depth, etc.
what is the sharing economy?
the name given to services which use new technology to let people make money from things they already own - e.g. Airbnb uses the internet to let you rent out a room in your house to tourists
what is an advantage of the sharing economy?
it makes things cheaper
what are some disadvantages of the sharing economy?
they draw customers away from original businesses, and they may be more risky for sharers and customers
what is the digital divide created by?
the fact that some people have greater access to technology than others
what are some examples of how people are advantaged by having access to the internet?
people can use the internet to apply for jobs or university courses, access a range of services from banking to retail, and keep in touch with friends. people who have a limited access to the internet are therefore at a heavy disadvantage
what are 3 causes of the digital divide?
- some people don’t have enough money to buy new devices like smartphones and laptops, which can be very expensive
- urban areas are likely to have greater network coverage than rural areas
- some people don’t know how to use the internet and other new technologies, and so are shut out of the opportunities they offer. this is a problem for many older people who haven’t grown up with computers and so have little experience with them
what is the global divide created by?
the fact that the level of access to technology is different in different countries. people in richer countries tend to have greater access to technology than people in poorer countries. the internet and other technologies have created lots of opportunities for the people with access to them, so this has increased the inequality between poorer and richer countries
what is One Laptop Per Child?
a charity which provides laptops to children in Africa, Central Asia and South America. it is one of the several projects that have been set up to combat the digital and global divides
give three examples of how technology and the internet have shaped our culture
- selfies - they’ve become really popular due to being able to take them and share them more easily, but they could be seen as a sign that social media is gradually making people more attention-seeking and self-obsessed
- viral videos - a big aim for companies, politicians, celebrities and charities in their promotional campaigns
- social media and blogging websites - give a voice to groups of people who might have been ignored my mainstream media
what is a protocol?
a set of rules for how devices communicate and how data is transmitted across a network
what information do protocols cover?
how communication between two devices should start and end, how the data should be organised, and what the devices should do if data goes missing
what does the TCP/IP protocol do?
dictate how data is sent between networks
what two protocols is the TCP/IP protocol made up of?
Transmission control protocol (TCP) and Internet Protocol (IP)
what does the transmission control protocol (TCP) do?
set the rules for how devices connect on the network. It’s in charge of splitting the data into packets and reassembling the packets back into the original data once they reach the receiving device. It’s also responsible for checking the data is correctly sent and delivered
what is the internet protocol (IP) responsible for?
packet switching
what is the Hyper Text Transfer Protocol (HTTP) used for?
used by web browsers to access websites and communicate with web servers
what is the HTTPS protocol?
a more secure version of HTTP. encrypts all information sent and received
what is the file transfer protocol (FTP) used for?
used to access, edit and move files between devices on a network e.g. to access the files on a server from a client computer
what does POP3 stand for?
Post Office Protocol - version 3
what is POP3 used for?
used to retrieve emails from a server. The server holds the email until you download it at which point it is deleted from the server
what does IMAP stand for?
Internet Message Access Protocol
what is IMAP used for?
used to retrieve emails from a server. The server holds the email until you delete it - you only download a copy. Used by most web-based email clients
what does SMTP stand for?
simple mail transfer protocol
what is SMTP used for?
used to send emails. Also used to transfer emails between servers
what is a layer?
a group of protocols which have similar functions
what is the name of layer 4?
application layer
what does layer 4 do?
turns data into websites and other applications and vice versa
what is the name of layer 3?
transport layer
what does layer 3 do?
controls data flow - e.g. splitting data into packets and checking packets are correctly sent and delivered
what is layer 2 called?
network layer
what does layer 2 do?
makes connections between networks, directs data packets and handles traffic. used by routers
what is layer 1 called?
data link layer
what does layer 1 do?
Passes data over the physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware
what protocols work in layer 4 (the application layer)?
HTTP, FTP, SMTP
what protocols work in layer 3 (the transport layer)
TCP (transmission control protocol)
what protocols work in layer 2 (the network layer)?
IP
what protocols work in layer 1 (the data link layer)?
ethernet
what are the advantages of using layers?
- it breaks network communication into manageable pieces. This helps developers to concentrate on only one area of the network without having to worry about others
- as layers are self-contained, they can be changed without the other layers being affected
- having set rules for each layer forces companies to make compatible, universal hardware and software, so different brands will work with each other and in basically the same way
what is the first principle of the data protection act?
data must only be used in a fair and lawful way
what is the second principle of the data protection act?
data must only be used for the specified purpose
what is the third principle of the data protection act?
data should be adequate, relevant and not excessive for the specified use
what is the fourth principle of the data protection act?
data must be accurate and kept up-to-date
what is the fifth principle of the data protection act?
data should not be kept longer than necessary
what is the sixth principle of the data protection act?
the rights of the data subject must be observed
what is the seventh principle of the data protection act?
data should be kept safe and secure
what is the eighth principle of the data protection act?
data should not be transferred abroad without adequate protection
what does the data protection act 1998 do?
it gives rights to data subjects
what is a data subject?
a person whose personal data is stored on computer systems
what does the data protection act mean for organisations?
- before collecting personal data an organisation must register with the government, saying what data they’ll collect and how they’ll use it
- the act gives data subjects the right to see the personal data an organisation holds about them
- there are some exceptions to this, e.g. organisations don’t have to disclose the data they hold if it could affect national security, tax assessment, or the outcome of a court case
- if a data subject feels an organisations use of their data has caused them distress, they may be entitled to compensation
what does the Freedom of Information Act 2000 allow?
public access to data - it allows members of the public to access information held by a public organisation about that organisation’s activities. The Act covers information stored in computer data files (including audio and video files), emails, and printed documents
what are some exceptions to the Freedom of Information Act 2000?
an organisation can withhold requested information if it is intended for future publication, or if disclosing it could affect national security or cause people harm
what does the computer misuse act 1990 prevent?
illegal access to files - it was introduced to stop hacking and cyber crime
what three new offences did the Computer Misuse Act 1990 introduce?
- Gaining unauthorised access to a private network or device, e.g. through hacking
- gaining unauthorised access to a network or device in order to commit a crime like stealing data or destroying the network
- unauthorised modification of computer material - e.g. deleting or changing files. The Act also makes it illegal to make, supply or obtain malware
what does the Copyright, Designs and Patents Act 1988 protect?
innovation - it was introduced to protect intellectual property - anything that someone has created
what does the Copyright, Designs and Patents Act 1988 make illegal?
it makes it illegal to share copyrighted files without the copyright holder’s permission, use unlicensed software of plagiarise somebody else’s work. Copyright holders can make money by granting permission to use the material for a fee
why has the internet made it harder to protect copyrighted content?
because of the ease of file sharing. It’s also difficult to enforce copyright if content is held on servers in countries with more relaxed copyright laws
what do Creative Commons licenses allow?
legal file sharing - they allow you to legally share media and software online without having to ask for permission first. Intellectual property owners use creative commons licences when they want other people to share of build upon their work
when does UK copyright expire?
70 years after the creators death, at which point their creation enters the public domain - Shakespeare’s plays, Beethoven’s symphonies and da Vinci’s paintings are all no in the public domain
what are the 2 types of images?
bitmap and vector
what are bitmap images mainly used for?
photos
how are bitmap images stored as binary?
Bitmap images are made up of lots of tiny dots, called pixels. The colour of each pixel is represented by a binary code. The number or colours available in an image is related to the number of bits the code has
what is colour depth?
the number of bits used for each pixel
what is the formula to work out how many colours can be made in an image?
total number of colours = 2^n (where n = number of bits per pixel, or bpp)
what colour depth do most devices use?
a 24-bit colour depth, with 8 bits used to indicate the levels of red, green and blue needed for each pixel. It is estimated that the human eye can see around 10 million different colours, so a 24-bit colour depth should cover every colour that you could possibly see
what is the resolution of an image? What is resolution normally measured in?
the density of pixels in an image, i.e. how many pixels are within a certain area. It’s normally measured in dots per inch (dpi)
what does increasing the resolution or the colour depth of an image mean?
that there are more bits in the image. This improves the image quality but also increases the file size
what is metadata? (images)
the information stored in an image file which helps the computer recreate the image on the screen from the binary data in each pixel. It usually includes the image’s file format, height, width, colour depth and resolution. It can also include extra information, like the time and date that the image was created or last edited. Without metadata, devices would not be able to display the image on screen as intended
what are the steps to sampling sound and storing it digitally?
- sound is recorded by a microphone as an analogue signal. Analogue signals are pieces of continually changing data
- analogue signals need to be converted into digital data so that computers can read and store sound files. This is done by analogue to digital converters, which are found in most modern recording devices
- the process of converting analogue to digital is called sampling: to convert the analogue recording to digital data, we sample the amplitude of the wave at regular intervals. The amplitude can only take certain values depending on the bit rate.
- once the device has sampled the recording, it creates the curve digitally
how is a digital sound wave similar/different to an analogue sound wave?
- the digital data is about the same shape as the analogue wave, but it’s not continuous. It’s lost a lot of data - the peak of the analogue wave is much flatter in the digital data
how can digital sound data be improved?
by taking samples more regularly - most music isn’t sampled every second but every millisecond
what are sampling intervals?
the gaps between each of the points where the analogue recording is sampled. E.g. the audio file might be sample every 5 milliseconds (ms), in which case the sampling interval would be 5 ms
what is sampling frequency (or sample rate)? What is it usually measured in?
how many samples you take in a second - it’s usually measured in kilohertz (kHz). E.g. a common sampling frequency is 44,100 samples per second (44.1 kHz)
what is sample size?
the number of bits available for each sample (like colour depth but for sound samples)
what is bit rate?
the number of bits used per second of audio
what is the formula for bit rate?
bit rate = sampling frequency x sample size
what is bit rate usually measured in?
kilobits per second (kbit/s)
what would happen if you increased the sampling frequency?
increasing the sampling frequency means the analogue recording is sampled more often. The sampled sound will therefore be better quality and will more closely match the original recording.
what will happen if you increase the sample size of a sound recording?
increasing the sample size means the digital file picks up quieter sounds, even if they’re happening at the same time as louder ones. This will also result in a sampled sound that is closer the the quality of the original recording.
what is a negative of increasing the sampling frequency and sample size?
a larger file size
what is data compression?
making files smaller, while trying to make the compressed file as true to the original as possible
what are the benefits of compression?
- smaller files take up less storage space on a device
- streaming and downloading files from the internet is quicker as they take up less bandwidth
- it allows web pages to load more quickly in web browsers
- email services normally have restrictions on the size of the attachment you can send - compressing the file allows you to send to same content with a much smaller file size
how does lossy compression work?
by permanently removing data from the file - this limits the number of bits the file needs and so reduces its size
how does lossless compression work?
lossless compression makes the file smaller by temporarily removing data to store the file and then restores it to its original state when it’s opened
what are the pros of lossy compression?
- greatly reduces file size, meaning more files can be stored
- lossy files take up less bandwidth so can be downloaded and streamed more quickly
- commonly used - lots of software can read lossy files
what are the cons of lossy compression?
- lossy compression loses data - the file can’t be turned back into the original
- lossy compression can’t be used on text or software files as these files need to retain all the information of the original
- lossy files are worse quality than the original, but this loss in quality is normally unnoticeable
what are the pros of lossless compression?
- data is only removed temporarily so there is no reduction in quality - the compressed file should look or sound like the original
- lossless files can be decompressed - turned back into the original
- lossless compression can be used on text and software files
what is the con of lossless compression?
there’s only a slight reduction in file size, so lossless files still take up quite a bit of space on your device. E.g. a lossless song may have a file size of around 30 MB, while the same song with lossy compression may be 5MB
give 3 examples of lossy file types
- MP3 (audio)
- AAC (audio)
- JPEG (image)
give 3 examples of lossless compression file types
- FLAC (audio)
- TIFF (image)
- PNG (image)
what is the purpose of the CPU?
to process data by fetching, decoding, and executing instructions
what is a register?
a small piece of memory that is volatile. It is directly accessed by the CPU and will store instructions, addresses or data
what is the purpose of the Memory Address Register?
to store the address of the next instruction/data to be accessed
what is the purpose of the Memory Data Register?
to store the data to be brought from/sent to main memory
what is the purpose of the program counter?
to store the address of the next instruction
what is the purpose of the accumulator?
to store the value currently being worked on/result of the last calculation
name 4 registers in the CPU
- memory address register
- memory data register
- program counter
- accumulator
what is the function of the ALU?
used to perform arithmetic calculations (e.g. +, -, *), used to perform logical operations (e.g. , =, !=)
what does ALU stand for?
Arithmetic and logic unit
what is the function of the control unit?
Transmits timing signals to manage and regulate actions such as reading and writing data, the input and output of data
what is the function of the cache?
Stores frequently used instructions and data, built onto the CPU, provides faster access than RAM, allows instructions and data to be loaded into the CPU more quickly.
What are three items that are stored in RAM?
- Programs currently in use.
- Data currently in use.
- OS currently in use
What is the main difference between RAM and ROM?
ROM is non-volatile and RAM is volatile
What is virtual memory?
- It is simulated memory that is written to a file on the hard drive
- memory that appears to exist as RAM but is in secondary storage.
Why is virtual memory needed?
When you need to run more/larger applications on the computer than its physical memory (RAM) can support.
It lets more memory be used than there is in the system.
How is virtual memory implemented?
- Operating system will set up virtual memory using the virtual memory manager (VMM).
- VMM creates a file on the hard disk large enough for the extra memory needed.
- OS can then address memory as if it were real memory stored in RAM.
- Maps memory addresses used by a program into physical addresses in computer memory.
- Swapping or paging is a process used by the operating system to move data between RAM and virtual memory.
- Operating system moves data when some processes are not needed immediately out of the RAM to store them in virtual memory (on the hard disk).
- Copies the data back into RAM when the process is needed again.
- Transfer between the two being made automatically as required
What does solid state media mean?
Storage media with no moving parts
Refers to removable storage with no moving parts
Device that uses flash memory
Why is secondary storage needed on a computer?
Used to back up data stored in main memory/primary storage.
Stores programs/data and other files that would otherwise be lost when the power is switched off/RAM is volatile/cannot store data permanently.
Need for larger storage capacity.
What are three advantages for using secondary storage?
Memory is non-volatile.
Data is not lost when the computer is switched off.
Stores larger amount of data.
name 3 types of secondary storage device
- optical
- magnetic
- solid state
How many bytes are in 3MB of data?
3 000 000 (3 million)
What is the highest value that can be represented by a nibble?
15
How many megabytes are there in 3 gigabytes?
3072 Megabytes or 3000Mb is acceptable.
What is a Pixel?
the smallest element that makes up an image
Why is metadata included in a file?
A computer needs to know the size of the image in terms of height, width and colour depth in bits per pixel (bpp) …this allows the computer to recreate the image from binary.
What is meant by a bit rate?
What is meant by a bit rate?
How can sound be sampled and stored in digital form?
Sound is continuously changing values (in analogue). The frequency is read at set intervals. Set values are saved and replayed. The sample rate affects the quality of the sound/ a high sample rate (or sampling sound at shorter intervals) improves the quality of the sound.
what are the advantages of compressing files?
Reduce download size. Reduce download time when transferring a file. Reduce storage requirement.
What is meant by lossy compression?
Removing data from a file (commonly images and sound) to reduce its size. Data is lost when file is uncompressed which means that the image cannot be restored to its original condition.
What is meant by lossless compression?
Compressing a file without losing any information. No bits are lost after the image has been restored. All data is restored after file has been uncompressed.
What are five advantages of networking computers?
- It is easy to share documents. Different users can work on the same document at once.
- Only one internet connection is required as it can be shared between every device connected to the network.
- Centralised backups can be carried out automatically.
- Software updates/patches can be automatically pushed out by the server to ensure that all devices are up to date.
- Users can log in to any machine connected to the LAN as accounts are stored centrally on the server.
What is the definition of ‘bandwidth’?
Bandwidth is the amount of data that can be transmitted in a given period of time
What does the acronym Mbps stand for?
Megabits Per Second.
Write about the impact that bandwidth can have on the performance of a network.
The amount of available bandwidth has a major impact on the performance of a network. The larger the amount of available bandwidth that is available the more data that can be transmitted in a given period of time.
If there is a large number of users on the network the amount of bandwidth available to each user may be limited. This will result in data being transmitted at a slower rate which will slow down the performance of the network.
Where large media files are being streamed the amount of available bandwidth is particularly important. Should a number of users be watching streaming HD content demand on bandwidth will be high. If there is insufficient bandwidth this could result in a reduction of quality in the video.
What is meant by the term ‘client server network’?
All devices are connected to a central server.
The central server receives and processes requests from ‘clients’.
The server stores user account details and files.
What are three reasons why you might choose a peer network model for a business?
All devices have equal status, there is no central server which makes them relatively easy to maintain.
There is no dependence on the server. If one device fails only the information stored on that device will be inaccessible. The network will still operate without that node.
They are relatively easy to set up without the need for a network manager.
A home internet connection goes through a hybrid device. What three network devices does it typically contain?
Router
Switch
Wireless access point
What is the purpose of a router?
To transmit data between at least two different networks
Many fast broadband connections use fibre optic cable instead of copper. What are three reasons why fibre optic cable is the preferred choice?
Fibre optic cables transmit data through light so do not suffer from electrical interference.
Data can be transmitted over very large distances without any loss of signal quality.
They are able to transmit data at a higher bandwidth.
You have a games console in your bedroom and a video streaming device in your lounge. You use both devices to watch movies. The Wireless Access Point is located in the lounge. You have found that you are able to stream movies at a far higher quality in the lounge than in your bedroom. Why is this?
The further the device is from the WAP the weaker the signal will be, so the lower the bandwidth will be.
Objects such as walls and doors will reduce the signal strength.
Other electrical devices could reduce the signal strength and interfere with the signal.
What are five reasons a Star network topology may be used to set up a new network?
They are very reliable.
If one connection fails it does not affect the rest of the network.
It is relatively easy to add additional devices onto the network.
It is relatively fast as each device has its own connection to the switch / server.
There are few data collisions.
What are five disadvantages of using a Star network topology instead of a Mesh network topology?
There is a high level of dependence on one single, central device.
If the central device fails the whole network will fail.
The use of a switch or router could increase the cost of the whole network.
The performance of the network will be dependent upon the specification of the central device/switch.
The number of additional devices that can be added to the network could be restricted by the central device/switch.
What is the definition of ‘protocol’?
A set of rules that govern how devices communicate.
What is the protocol that is used to transmit data between different networks?
Transmission Control Protocol / Internet Protocol. TCP/IP
What is the difference between HTTP and HTTPS?
HTTP transmits data over the internet in an unsecure format whereas HTTPS uses encryption so that any data that is intercepted is meaningless.
Data is transmitted across a network in packets. What are five items that each data packet will contain?
Network address source Network address destination Packet number / sequence Error detection codes Payload
what is IMAP used for?
it’s used to retrieve emails
what is SMTP used for?
it’s used to send emails
what is HTTP used for?
it’s used by web browsers to communicate with web servers
Protocols are divided into layers. Why are layers used?
Network communication components are standardised which helps to ensure that different types of hardware and software are able to communicate.
Through separating the overall network communication processes it makes troubleshooting easier should an error occur.
To ensure that if changes are made in one layer they do not affect any other layers
Through dividing overall network communication into smaller, individual components it makes the software development process more straightforward.
Packet switching is used to send data on the internet. How does packet switching work?
Data is split into individual packets.
Each packet is given a packet number which shows the numerical order of the packet.
The router reads the packet and sends it on to the next location.
The receiving device will read the packet number and reassemble the data in the correct order.
As the device reassembles the data from the packets if a packet is missing it will send an error message to the sending device requesting that the packet is resent.
The sending device will resend the packet.
Once all of the packets are received and reassembled the receiving device will calculate the checksum to ensure that none of the data has become corrupted.
A confirmation message will send from the receiving device to the sending device.
What is the difference between an IP address and a MAC address?
A MAC address is permanently assigned to a device on the network whereas an IP address may change when the device joins a different network.
What is the difference between IPv4 and IPv6 addresses?
IPv4 – 4 blocks of denary digits between 0 and 255 Values separated by full stops.
IPv6 – 8 blocks of 4 hexadecimal digits Values separated by colons.
list the steps to the encryption process
- client requests HTTPS session
- certificate sent to client from the server
- client creates session key
- encrypted session key is sent to the server
- the session key is decrypted with the private key
- session is encrypted with the session key
What is the purpose of POP3?
To retrieve emails, only award the mark for retrieve (or similar). The protocol cannot be used to send emails.
give 10 methods that could be used to infect a laptop with malware
10 from: [] Software that was installed from an untrustworthy source, for example, screensavers, etc. Existing anti-malware software is out of date Out of date system software/application software Out of date browser Out of date firewall Infected removable drives Exploitation of a software vulnerability Various social engineering techniques, e.g. phishing Scareware Infected email attachment Infected link Spam email A hacked website Fake website Popup software Illegal file sharing Distributed denial of service Adware Rootkits
What are three types of anti-malware that should be used to protect a laptop?
[] Anti-virus
Anti-spyware
Malware scanner
How could phishing take place at a business?
Staff respond to fake email
Staff respond to fake link
Staff respond to fake website
Staff respond to spam
Staff respond to popup software fake instant messages
Staff respond to social media messages, ‘likes’, etc.
What are six potential problems to a business if phishing takes place?
Acquisition of user names and passwords
Acquisition of financial details/credit card details
Identity theft
Data theft
Staff disclose personal/confidential data
Financial data theft
Give 8 examples of social engineering other than phishing that employees at a business should be aware of.
Pharming Blagging/pre-texting Shoulder surfing Baiting scenarios Countermeasures Tailgating Quid-pro-quo Hoax viruses
What is meant by the term ‘brute force attack’?
An attack that attempts to decode passwords/encryption keys/encrypted
data
All possible/numerous combinations are attempted
A trial and error method
Resource/time consuming method
What are eight features of a strong password?
At least eight characters Include upper case Include lower case Include special characters Include numbers Does not include a name, company name or user name Does not contain a complete word Relates to an acronym
What are nine measures in addition to a password that could be used to keep a computer’s data secure?
Encryption/encrypt data Set a PIN/pattern to lock the phone Install security software Download apps from trusted sources Keep the operating software and apps updated Log out of sites Turn off automatic Wi-Fi connection Turn off Bluetooth and NFC when not in use Biometrics
What are ten reasons why companies may be targeted by a denial of service attack?
Protest/hacktivism Cyber vandalism Distraction technique Espionage – commercial, industrial. political Can lead to malware/data theft if part of a distraction technique If a distributed denial of service attack can lead to computer/network control Extortion Competition between companies Make a website unavailable Interrupt an organisation’s work Suspend an organisation’s work Block user requests
What are five measures that a company could take to prepare for a denial of service attack?
Networks should be monitored
Penetration testing should be undertaken/vulnerabilities should be found
Vulnerabilities should be fixed/remedied
A response plan should be produced
Proxy servers and firewalls
What is one method that a business could use to ensure that sensitive documents will not be read by anyone except the intended recipient?
Encryption.
What are 6 reasons why an attacker might want to target an organisation’s database with an SQL injection?
Access sensitive data Steal/retrieve personal data Access/steal/retrieve financial data Create/read/update/modify/delete data Destroy data Take control of data
What are six measures that an organisation should take to guard their software applications from an SQL injection attack?
Limit user access/privileges Create user accounts Apply input sanitation Apply an input validation technique Apply patches/software updates Install web application firewall/strong web application firewall
What are eight advantages of using a firewall?
Controls network traffic/allows data from authorised Blocks data from unauthorised sources Protects against attackers Offers different protection levels Protects privacy Provides warnings Filters advertisements/popups Filters web content
Give a comparison of intrusion detection and vulnerability testing.
Intrusion detection monitors a network for unauthorised access by an
attacker.
Intrusion detection identifies unauthorised access after an attacker has
breached a network’s security.
Vulnerability testing scans a network for vulnerabilities.
Vulnerability testing detects vulnerability before an attack occurs.
How would penetration testing help to secure a company’s computer network?
Penetration testing looks for vulnerabilities.
It attempts to exploit the vulnerabilities that it finds.
The results of penetration testing are presented to network managers to
help them to remedy the vulnerabilities
It helps to protect a system from cyber attacks
It identifies and prioritises security risks
It helps to save money/resources
It helps to avoid down time
It helps to protect a company’s reputation
What are four ways of physically protecting a network?
Door locks Window locks or bars Intruder alarm systems CCTV systems Laptop locks (e.g. Kensington locks) Security guards
What is the definition of ‘bandwidth’?
Bandwidth is the amount of data that can be transmitted in a given period of time
What does the acronym Mbps stand for?
Megabits Per Second.
Write about the impact that bandwidth can have on the performance of a network.
The amount of available bandwidth has a major impact on the performance of a network. The larger the amount of available bandwidth that is available the more data that can be transmitted in a given period of time.
If there is a large number of users on the network the amount of bandwidth available to each user may be limited. This will result in data being transmitted at a slower rate which will slow down the performance of the network.
Where large media files are being streamed the amount of available bandwidth is particularly important. Should a number of users be watching streaming HD content demand on bandwidth will be high. If there is insufficient bandwidth this could result in a reduction of quality in the video.
A home internet connection goes through a hybrid device. What three network devices does it typically contain?
Router
Switch
Wireless access point
You have a games console in your bedroom and a video streaming device in your lounge. You use both devices to watch movies. The Wireless Access Point is located in the lounge. You have found that you are able to stream movies at a far higher quality in the lounge than in your bedroom. Why is this?
The further the device is from the WAP the weaker the signal will be, so the lower the bandwidth will be.
Objects such as walls and doors will reduce the signal strength.
Other electrical devices could reduce the signal strength and interfere with the signal.
What is the definition of ‘protocol’?
A set of rules that govern how devices communicate.
What is the protocol that is used to transmit data between different networks?
Transmission Control Protocol / Internet Protocol. TCP/IP
What is the difference between HTTP and HTTPS?
HTTP transmits data over the internet in an unsecure format whereas HTTPS uses encryption so that any data that is intercepted is meaningless.
what is IMAP used for?
it’s used to retrieve emails
what is SMTP used for?
it’s used to send emails
what is HTTP used for?
it’s used by web browsers to communicate with web servers
What is the difference between an IP address and a MAC address?
A MAC address is permanently assigned to a device on the network whereas an IP address may change when the device joins a different network.
What is the difference between IPv4 and IPv6 addresses?
IPv4 – 4 blocks of denary digits between 0 and 255 Values separated by full stops.
IPv6 – 8 blocks of 4 hexadecimal digits Values separated by colons.
list the steps to the encryption process
- client requests HTTPS session
- certificate sent to client from the server
- client creates session key
- encrypted session key is sent to the server
- the session key is decrypted with the private key
- session is encrypted with the session key
What is the purpose of POP3?
To retrieve emails, only award the mark for retrieve (or similar). The protocol cannot be used to send emails.
What are three types of anti-malware that should be used to protect a laptop?
[] Anti-virus
Anti-spyware
Malware scanner
What are eight features of a strong password?
At least eight characters Include upper case Include lower case Include special characters Include numbers Does not include a name, company name or user name Does not contain a complete word Relates to an acronym
What are nine measures in addition to a password that could be used to keep a computer’s data secure?
Encryption/encrypt data Set a PIN/pattern to lock the phone Install security software Download apps from trusted sources Keep the operating software and apps updated Log out of sites Turn off automatic Wi-Fi connection Turn off Bluetooth and NFC when not in use Biometrics
What are five measures that a company could take to prepare for a denial of service attack?
Networks should be monitored
Penetration testing should be undertaken/vulnerabilities should be found
Vulnerabilities should be fixed/remedied
A response plan should be produced
Proxy servers and firewalls
What is one method that a business could use to ensure that sensitive documents will not be read by anyone except the intended recipient?
Encryption.
What are six measures that an organisation should take to guard their software applications from an SQL injection attack?
Limit user access/privileges Create user accounts Apply input sanitation Apply an input validation technique Apply patches/software updates Install web application firewall/strong web application firewall
What are eight advantages of using a firewall?
Controls network traffic/allows data from authorised Blocks data from unauthorised sources Protects against attackers Offers different protection levels Protects privacy Provides warnings Filters advertisements/popups Filters web content
Give a comparison of intrusion detection and vulnerability testing.
Intrusion detection monitors a network for unauthorised access by an
attacker.
Intrusion detection identifies unauthorised access after an attacker has
breached a network’s security.
Vulnerability testing scans a network for vulnerabilities.
Vulnerability testing detects vulnerability before an attack occurs.
How would penetration testing help to secure a company’s computer network?
Penetration testing looks for vulnerabilities.
It attempts to exploit the vulnerabilities that it finds.
The results of penetration testing are presented to network managers to
help them to remedy the vulnerabilities
It helps to protect a system from cyber attacks
It identifies and prioritises security risks
It helps to save money/resources
It helps to avoid down time
It helps to protect a company’s reputation
What are four ways of physically protecting a network?
Door locks Window locks or bars Intruder alarm systems CCTV systems Laptop locks (e.g. Kensington locks) Security guards
what is the difference between a protocol and a standard?
A protocol defines a set of rules used by two or more parties to interact between themselves. A standard is a formalized protocol accepted by most of the parties that implement it.
what is a standard?
standards are an agreed way of doing things. Standards make it easier for people to build programs and software that work on different systems in different countries. Standards affect many areas of computing, eg software files, formats and hardware.
What is meant by an ethical issue?
What is considered to be right and wrong by society.
What is meant by the digital divide?
Division which exists between those individuals who can use technology and those who are not. Differences in access to technology. Groups having more access to technology compared to other groups. Reasons include: o money o internet access o location o training o disability.
What are the ethical issues involved with the introduction of driverless cars?
Who is to blame in an accident?
In an emergency situation who should the car prioritise?
Increase in use of cars is bad for the environment.
Cost of the cars.
How does artificial intelligence impact on the medical profession?
Job replacement Higher level of accuracy More reliable Cost Improves diagnosis and treatment of patients
What is internet censorship?
Control of what can be accessed, published, or viewed on the internet.
How does the use of technology impact on the environment?
Increased use of electricity
Use of natural resources
E-waste
How can e-waste be managed to limit any impact on the environment?
Appropriate disposal. Increased recycling. Refurbishing of devices. Refurbishing of materials. Changes in warranty e.g. longer warranty so people are more likely to keep devices.
More and more automation is being introduced into the workplace such as in retail or manufacturing. What are the ethical, environmental and cultural impacts of this?
Job replacement Accuracy Increase use of electricity Health issues Increased speed Cheaper in the long run
What year was the Data Protection Act last updated?
2018
What are the principles of the Data Protection Act?
Data must be collected and used fairly
Data must only be held and used for the reasons which it was gathered
Data can only be used for registered purpose
Data held must be adequate, relevant and not excessive
Data must be accurate and up to date
Data cannot be kept for longer than necessary
Data must be kept safe and secure
Data cannot be transferred outside of the EU unless they have a suitable DPA
law
What offences are illegal under the Computer Misuse Act?
Access computer systems without proper authorisation
Access computer systems with intent to commit a criminal offence
Alter data without permission
What are three examples of work covered by the Copyright Designs and Patents Act?
three from: Songs Books Software Music Film Video games
You purchase a CD. Under the Copyright Designs and Patents Act, what four things are illegal for you to do with or use the CD for?
Giving a copy to someone else
Selling a copy to someone else
Renting a copy to someone
Using it on a network
What is meant by an ethical issue?
What is considered to be right and wrong by society.
What is meant by the digital divide?
Division which exists between those individuals who can use technology and those who are not. Differences in access to technology. Groups having more access to technology compared to other groups. Reasons include: o money o internet access o location o training o disability.
What is internet censorship?
Control of what can be accessed, published, or viewed on the internet.
How does the use of technology impact on the environment?
Increased use of electricity
Use of natural resources
E-waste
How can e-waste be managed to limit any impact on the environment?
Appropriate disposal. Increased recycling. Refurbishing of devices. Refurbishing of materials. Changes in warranty e.g. longer warranty so people are more likely to keep devices.
What year was the Data Protection Act last updated?
2018
What are the principles of the Data Protection Act?
Data must be collected and used fairly
Data must only be held and used for the reasons which it was gathered
Data can only be used for registered purpose
Data held must be adequate, relevant and not excessive
Data must be accurate and up to date
Data cannot be kept for longer than necessary
Data must be kept safe and secure
Data cannot be transferred outside of the EU unless they have a suitable DPA
law
What offences are illegal under the Computer Misuse Act?
Access computer systems without proper authorisation
Access computer systems with intent to commit a criminal offence
Alter data without permission
What are three examples of work covered by the Copyright Designs and Patents Act?
three from: Songs Books Software Music Film Video games
You purchase a CD. Under the Copyright Designs and Patents Act, what four things are illegal for you to do with or use the CD for?
Giving a copy to someone else
Selling a copy to someone else
Renting a copy to someone
Using it on a network
does a 1 mean electricity is flowing or isn’t flowing?
is flowing
does a 0 show that electricity is flowing or that it isn’t flowing?
that it isn’t flowing
what is a byte big enough to store?
one character
what is the file size of most files (like songs, pictures and documents) measured in?
kB or MB
what are high definition videos and complex applications often measured in?
gigabytes
what is secondary storage capacity measured in?
gigabytes or terabytes
why is each unit 1024 (not 1000) times bigger than the previous unit?
because 1024 is a power of 2 which is helpful when dealing with binary data
what is the formula to find out how many different values a data unit can take?
2^n where n is the number of bits
what are check digits used for?
check digits are a way of checking that data has been entered and read correctly. They are digits added to the end of numbers (e.g. ISBNs on books) and are calculated using other digits in the number. If the check digit is correct when data is read, then it’s likely that the data has been entered/read correctly
which denary numbers can 8-bit binary numbers represent?
the denary numbers 0 to 255
which denary numbers can 16-bit binary numbers represent?
the numbers 0 to 65,535
which denary numbers can 32-bit binary numbers represent?
the numbers 0 to 4,294,967,295
when do overflow errors occur?
when a calculation gives a result with more bits than are available to store it. This can be a real problem - programmers must make sure that they can’t occur, or that they are dealt with.
what is used to show that an overflow error has occured?
overflow flags
why are overflow errors a problem?
they can lead to a loss of data and a loss of accuracy in your answer. It could also cause software to crash if it doesn’t have a way of dealing with the extra bit.
what does a binary shift do?
it moves every bit in a binary number left or right a certain number of places
what is another name for a binary shift?
a logical shift
what happens to gaps at the beginning or end of the number in a binary shift?
the gaps are filled in with 0s
what do left shifts (binary shifts) do?
multiply a binary number. For every place shifted left, the number is doubled.
what do right (binary) shifts do?
they divide a binary number. For every place shifted right, the number is halved
how many bits is each hex character equal to?
4 bits (a nibble)
what are the advantages of using hexadecimal?
- it’s simpler to remember large numbers in hex - they’re far shorter than binary numbers
- due to hex numbers being shorter, there’s less chance of input errors
- it’s easier to convert between binary and hex than binary and denary
what do you do if, when you are converting binary to hexadecimal, you can’t split the binary number evenly into nibbles?
you add 0s on the front until there is an exact number of nibbles
What hardware is needed to connect a stand-alone computer to a LAN?
[] A network adapter such as a network interface card (NIC) is needed to connect computers and other peripherals to a network, either by cable or wirelessly. Each connected device is allocated an IP address to uniquely identify it on a TCP/IP network.
[] Cabling is needed in a non-wireless network to connect the computers and peripherals together, either directly or through a hub/switch. Typically network cabling will be copper wiring or a mixture of this and fibre-optic cable. The amount of cabling needed depends on the network topology
[] A hub is used to link computers and peripherals together in a cabled network that uses a star network topology. A hub a junction box but does not manage any of the traffic that comes through it, any data packet entering any port is sent out to all the connected ports. This can result unnecessary data packet collisions which slow the network considerably as the amount of data traffic rises.
[] A switch is used in the same way as a hub but the switch uses the IP address of the data packet to direct the data to the correct device, rather than being sent out to all the connected ports. This greatly reduces data packet collisions resulting in a faster network than the equivalent one using a hub.
[] A wireless access point is a device that allows computers and printers etc. to connect to a wired network using radio waves rather than cabling, provided they are equipped with a wireless NIC. This allows a network to built with few or no cables and makes it simple to add further wireless devices.
