Last minute essential revision notes for Cambridge IGCSE ICT (0417)

1. Prepared and Compiled by Yash Bhatt 10 April 2016
ICT Notes
Explain why backing storage is needed.
If computer is switched off, work in RAM is lost but backing storage stores data for future use
More likely that data is accidentally deleted in RAM
RAM is more expensive than backing storage per unit of memory
RAM is bulkier than backing storage per unit of memory
Software package may be so large that it is physically impossible for RAM to store it.
Operating system may be so large that it is physically impossible for ROM to store it.
Data may need to be transferred from one computer to another and can’t do that with RAM
Describe why main/internal memory is needed.
Memory is needed which cannot be changed – ROM
Memory is needed which can be changed – RAM
Instructions that need to be unchanged have to be stored such as BIOS/ program cycles in a
washing machine/program instructions in games
There needs to be memory that holds the work that is being currently done by the user
There needs to be memory that holds the software that is being currently used by the user
Non-volatile memory is needed – ROM
What is an Expert system?
Expert System is a computer program which uses databases of expert knowledge to offer advice or make
decisions in areas such as medical diagnosis. They are designed to solve complex problems.
Describe how expert system is created.
Data is gathered/collected from experts
Knowledge base is designed/created
A structure to relate each item in the database/knowledge base is created
An interrogation technique to access the data is created
A user interface/method of displaying the results/method of inputting data/input
screen/output screen is designed/created
The inference engine is designed/created
The rules base is designed/created
The system is tested
Example of expert systems
Prospecting
Tax
Careers
Chess games
Animal/plant classification/identification
Advantages and Disadvantages of expert systems
Advantages:
 They provide consistent answers and are not affected by emotional reasoning.
 They never forget to answer a question when determining logic.
 It reduces the time taken to solve a problem.
 The potential of saving money exists since there is less need for specialists.
 They indicate the probability of the given solution being accurate or correct.

2. Prepared and Compiled by Yash Bhatt 10 April 2016
Disadvantages:
 They tend to lack common sense in some of the decision making process.
 Lack of emotional reasoning can be a disadvantage in areas such as medical diagnosis,
 Errors in the knowledge base can lead to incorrect decisions being made.
 They can be expensive to set up.
What is copyright?
Lawful protection....
......Given to authors of software /companies /publishers
Relates to the software/name/work the author/publisher/company created/published
Prohibits purchaser from making unlimited copies/lend it to others/change the software/sell
software/books/intellectual property without the company’s/author’s permission
What are passive and active attacks?
Passive attacks include the release of email material to other users without your consent. Active attacks involve
the modification of your messages or even denial of service, it overloads the system by sending thousands of
emails which clogs up the computer and makes the internet access impossible.
What is Netiquette?
Netiquette is a shortened form of the phrase internet etiquette, which refers to the need to respect other users’
views and display common courtesy when posting views in online discussion groups or when sending emails.
What is Intranet?
It is defined as computer network based on internet technology but designed to meet internal needs for sharing
information within a single organization or company.
What is Cloud storage?
Cloud storage is a method of data storage where data is stored on offsite servers.
What is HTTP?
Hypertext transfer protocol is a set of rules that must be obeyed when transferring data across the internet.
What is a web browser?
A web browser is software that allows user to display a web page on their computer screen.
What is a file transfer protocol?
A file transfer protocol is a network protocol used when transferring files from one computer to another computer
over the internet.
What are Blogs?
Blogs (web logs) are personal internet journals where the writer will type in their observation on some topic and
perhaps provide links to some relevant websites.
What are Microblogs?

3. Prepared and Compiled by Yash Bhatt 10 April 2016
Microblogs are similar to blogs but are most often used on social networking sites to make short, frequent posts.
B-blog short for business blog; it is used by businesses to promote themselves on the internet.
What are Wikis?
Wikis are web application or websites that allow users to create and edit web pages using any web browser.
Entries aren’t usually in chronological order.
What are social networking sites?
Social networking sites focus on building online communities of users who share the same interests and activities.
What are search engines?
Search engines use the words entered in the search box and look up in the database of web pages to find out
which of them match the search string.
What is a control system?
Control system is a device or set of devices which manages, commands, directs or regulates the behaviour of
another devices or systems to achieve a desired result.
Describe how a microprocessor-controlled burglar alarm system operates
Microprocessor checks input from the user is authentic
Microprocessor continually monitors sensors.
If infra-red sensor reading changes
If pressure greater than pre-set value...
If sound greater than pre-set value...
Microprocessor sends signal to sound alarm
Microprocessor sends signal to flashing light/house lights.
Microprocessor automatically sends message/calls/texts owner
What is meant by GPS?
Global Positioning System
– space-based navigation system
– typically four satellites must be visible to the receiver
– calculates the distance from a receiver to the satellite
– calculates the position of the receiver
Describe the role of the microprocessor in an automatic washing machine.
Microprocessor is programmed with pre-set values
Microprocessor starts cycle at specified time
Microprocessor reads data from sensors
Checks contact switch on door is closed
If it isn’t microprocessor will not start the cycle/if it is microprocessor starts cycle
Microprocessor compares sensor readings with pre-set value
If temperature is above pre-set value, microprocessor switches off heater
If temperature is below pre-set value, microprocessor switches on heater
If pressure is greater than preset value, microprocessor sounds alarm
Microprocessor checks pressure reading and calculates the amount of water to use
At start of cycle, microprocessor opens valve to let in water
If water level reached, microprocessor switches off valve
Microprocessor ends cycle at specified time

4. Prepared and Compiled by Yash Bhatt 10 April 2016
Describe the effects on people’s lifestyles of the use of microprocessor-controlled devices in the home.
Microprocessor controlled devices do much of housework
Do not need to do many things manually
Do not need to be in the house when food is cooking
Do not need to be in the house when clothes are being washed
Can leave their home to go shopping/work at any time of the day
Greater social interaction/more family time
More time to go out/more leisure time/more time to do other things/work
Are able to do other leisure activities when convenient to them
Can lead to unhealthy eating due to dependency on ready meals
Can lead to laziness/lack of fitness
Can encourage a healthy lifestyle because of smart fridges analyzing food constituents
Microprocessor controlled burglar alarm provides a sense of security
Do not have to leave home to get fit
Manual household skills are lost
Describe how a microprocessor uses the data from input devices to control an automatic cooker.
Microprocessor stores required temperature as preset value
Microprocessor stores cooking time/start time as preset value
End times as preset values
Microprocessor subtracts cooking time from end time
Microprocessor compares the result with current time
If the current time and the start/calculated time are the same microprocessor switches on heater
Microprocessor compares temperature from sensor to pre-set temperature
If temperature is lower than preset value microprocessor sends a signal to actuators…
…to turn heater on
If higher than preset value microprocessor sends a signal to actuators…
…to turn heater off
Microprocessor compares current time with end time/start time preset value
If current time is less than end time presetvalue then cycle continues else…
…microprocessor sounds buzzer/beeper
Describe how the computer would monitor the level of pollution in the river.
The sensors feed back/send data to microprocessor/computer
Data is converted from Analogue to Digital/sent through an ADC
Readings from above the factory are compared with those from below factory…
...by the computer/microprocessor
Differences/results are printed out
Graphs are automatically produced by computer showing values from below and above
factory…
...plotted against time
Process is continuous
What is user id and password?
User Id is an ID given to each user which identifies the user in the system and allows the system to assign
privileges whereas password allows the user to gain access to the system if it matches the user name.
Describe four items which can be provided by an ISP.
Access to the internet
Email address
Router to connect to the internet
Domain name to have own website

5. Prepared and Compiled by Yash Bhatt 10 April 2016
Email security software
Web space to create own website
Storage space to save data in the cloud
DNS service to convert URLs to IP addresses
Firewall to block unauthorised traffic
Explain why financial models (or any model) are often used to predict future profitability.
Easier to modify/change data/variables
Costs less to change data/variables
The real thing may be impossible to create
You can test predictions more easily/model can make predictions more accurately
You can ask many what if questions which would be impractical in real life
Results are obtained more quickly
Explain why encryption is needed when transmitting data.
Encryption is the protection of sensitive data. It causes the data to get scrambled or encoded. Encryption is
needed because the data can fall in wrong hands. Computer can only understand the data, if it has the key.
Give three reasons why files are backed up.
In case original data is accidentally deleted
In case data is maliciously deleted
In case original data is corrupted
To recover a previous version of a file
Give three specific examples of work that are carried out by a robot in the car industry.
Putting wheels on cars
Painting car bodies
Welding parts on a car body
Carrying car windscreens/doors
Moving goods in an automatic warehouse
Placing engine block into body
Installing transmission system
Explain, using examples, what is meant by authentication techniques.
Authentication techniques involve the use of user ID, passwords and biometrics to identify the user in a system.
Magneitc cards, PIN, biometrics are all examples of authentication techniques.
Describe the differences in use between WiFi and Bluetooth.
WiFi helps to establish a local area network and provides internet access to the user. Using WiFi, Laptops and
desktop computers can connect to the wireless routers. Bluetooth connects two devices together. Adding further
Bluetooth peripherals are powered by battery therefore it needs to be charged and replaced.WiFi covers larger
distance than Bluetooth and needs ten times more bandwidth than Bluetooth.
Compare and contrast the use of optical discs and the use of fixed magnetic disks to store data.
Optical discs such as CDs DVDs and Blu-ray discs…
…are read from and written to using a laser beam
Magnetic disks are read from and written to using read/write heads
Optical discs are more portable
Magnetic disks are more likely to spike

6. Prepared and Compiled by Yash Bhatt 10 April 2016
Optical discs are cheaper to buy
Magnetic disks store more data
Optical discs have slower access times
Optical discs have slower transfer rates
Optical discs can be more easily lost/stolen
Optical discs can be more easily scratched
Both store videos, music
Both use direct access
Examples of types of modelling
Simulations
Mathematical models
Civil engineering models
Flight/pilot simulation/training
Design of fairground rides
Traffic control
Building fire simulation
Weather forecast models
Population modelling
Describe four features of a website that will prove that the information found on it is reliable.
Can use the final part of a URL to identify reliability
.ac, .gov, .org are usually fairly reliable
If information matches that from reliable sites or reliable/authenticated text books
If responsible bodies have endorsed the site information will be reliable
If it has links to other reliable sites then information will be reliable
If site has testimonials it is likely to be reliable
If the author’s credentials are good it is likely to be reliable
Describe three other features of a website that may indicate that the information found on it is
not likely to be reliable.
If site has excessive advertising it could be unreliable
If the advertising is related only to its own products it could be unreliable
If the date of the last update was a long time ago it is likely to be unreliable
If it has links to other unreliable sites it could be unreliable
Give four benefits of using social networking sites.
Easy to keep in immediate contact with friends/make new friends
Easy to communicate to more than one friend/to communicate with people overseas
Can search for people who you’ve fallen out of touch with
Easy to arrange meetings/visits to cinemas/theatre
Can share photographs/videos/images/opinions/views
What is batch processing?
This is where number of similar jobs and tasks are collected together and processed by a computer all at once
rather than individually. It can take long time to perform. Eg: Payroll, producing bills, stock control.
What is online processing?
It is a type of processing where the user communicates directly with the computer system.Eg: Booking system,
ATM’s.

7. Prepared and Compiled by Yash Bhatt 10 April 2016
What is real-time processing?
Real-time processing uses sensors rather human input in order to obtain its data.Eg: Aircraft warning system and
automatic greenhouses, burglar alarms.
What are Modems, Hubs and switch,bridge, router, gateway, NIC?
Modem means modulator demodulator and is a device that converts computer’s digital signal into an analogue
signal for transmission over an existing telephone line. It also does the reverse process, in that it converts
analogue signals from telephone line into digital signals.
Hubs are hardware devices that can have number of devices or computers connected to them. They are often
used to connect together a number of devices to form a LAN. Data packet sent to hub is sent to all workstations or
computers.
Switch is similar to hub but data packet sent to a switch is sent to the recipient only.
Bridge is network hardware that connects one LAN to another LAN that uses the same protocol.
Router allows the data to be routed between two dissimilar networks
A gateway is a network point that acts as an entrance to another network.
Netowrk interface card(NIC) allows the device to connect to the network.
What is the difference between IP and MAC address?
IP and MAC addresses are both a unique address given to a device connected on the internet, however the IP
gives the locaton of the device on the internet whereas MAC address identifies the device connected to the
internet.
What is EFT?
Electronic funds transfer is a system that allows money transfer instructions to be sent directly to a bank’s
computer system.No actual money transfer is transferred; the whole system relies on electronic transfer of money
between accounts.
Advantages and disadvantages of online shopping and banking
Advantages:
 No need to travel, hence travelling costs and time is saved. It also reduces congestion and pollution
 Users now have access to worldwide market and can thus look for products which are cheaper. They also
have access to wide range of products.
 Disabled and elderly people can now access any shop or bank without the need to leave home.
 Online shopping and banking can be anytime on any day of the week (24/7)
 People have more free time and can perform leisure activities, as online shopping and banking takes very
less time.
Disadvantages:
 There is a possibility of isolation and lack of socialization if people stay at home and do online shopping
and banking.
 There are possible health risks associated with online shopping and banking because of lack of excericise.

8. Prepared and Compiled by Yash Bhatt 10 April 2016
 Security issues are major concern such as hacking, stealing credit card details and phishing.
 It is necessary to have a computer and internet access to take part in online shopping or banking.
 There is no direct contact with seller and the goods bought. There can be a huge difference between
goods displayed on the website and the actual goods delivered.
 User also has to wait for the goods to arrive and returning them is also expensive.
Advantages and disadvantages of using robots as automation.
Advantages:
 They can work in environments harmful to human operators.
 They can work non-stop(24/7)
 They are less expensive in the long term
 Higher productivity and greater consistency
 They can do boring and repetitive jobs leaving humans free to do more skilled work.
Disadvantages:
 They can cause higher unemployment
 The initial set up and maintenance of robots can be expensive.
 As humans are replaced by the robots; there is a risk of certain skills being lost.
Advantages and disadvantages of online booking systems.
Advantages:
 Double booking is prevented which occurs in paper based systems which don’t update the system fast
enough.
 The user gets an immediate feedback on the availability of seats and whether or not their booking has
been successful.
 Booking can be done any time of the day.
 Special offers can be sent to customer’s email address to inform them quickly and automatically.
 Printing cost of tickets is saved as the customer is sent a QR code which contains all the booking
information. Customers need to scan their QR code at the theatre or the cinema on arrival.
Disadvantages:
 The initial set up and maintenance of the booking system is expensive
 Customers need to have a computer and a reliable internet connection.
 It is often more difficult to cancel the booking and get the money back as a refund.
 If the server is down for maintenance or if it breaks down then online booking isn’t possible
What are user and technical documentation and what it consists of?
User documentation is designed to help users to learn how to use the software or system. It consists of:
 How to save files
 How to add, delete or amend records
 Hardware requirements
 Software requirements
 How to load/install/run

9. Prepared and Compiled by Yash Bhatt 10 April 2016
Technical documentation is designed to help programmers and analysts to make improvements to the system or
to repair or maintain the system. It consists of:
 Programming language used
 Limitations of the system
 Program flowcharts/algorithms
What is hacking?
Hacking is the act of gaining unauthorized access to a computer system. It can lead to identity theft and misuse of
personal information. Data can be deleted, changed or corrupted on a user’s computer. It can be prevented by the
use of firewalls, strong passwords and user IDs, and intrusion detection software.
Effects of hacking:
 Identity Theft – Some hackers can gain access to sensitive information which could be used to fuel identity
theft
 E-mail Access – Hackers have the ability to gain access to personal e-mail accounts. These can have a
variety of information and other private files which most people would regard as important. Information can
be a very sensitive data which can lead to identity theft.
 Website Security – Many websites have been victims of hackers. Usually the hackers would simply
destroy data and leave the websites in an inoperable state which would leave website owners with the task
of rebuilding their sites from scratch if they did not have a backup.
What is Phishing?
It’s a fraudulent practice in which the creator sends out legitimate looking emails to target users. As soon as the
recipient clicks on a link in the email attached, they are sent to fake website or they are fooled into giving personal
data in replying to the email. The email often comes from a trusted source such as a bank. They creator of the
email can gain personal data such as bank account details or credit card numbers from the user, it can also lead
to fraud or identity theft.
What are Spear phishing attacks?
Spear-phishing defines a more specialized phishing scheme. It’s an attempt by a hacker to obtain confidential
information about a user through fraudulent means targeting a specific employee in order to gain access to a
company’s information. In order to do this, an email that appears to come from inside the company or another
trusted source is sent to the targeted person. This email must also contain convincing information that appears to
be from a trusted source. As with phishing, the target will be requested to click a link to be brought to a bogus
website in order to get them to enter in their sensitive information. Sometimes, just clicking the link is enough to
install malware on the target’s machine, which may allow the attacker to take control of their computer and
continue their scheme.
What is Smishing?
Smishing uses the SMS system of mobile phones to send out fake text messages. It is very similar to phishing.
These scams often contain a URL or telephone number embedded in the text message. The recipient will be
asked to log on to the website or make a telephone call to provide their personal details. As with phishing attacks
the text message will appear to come from a legitimate source.

10. Prepared and Compiled by Yash Bhatt 10 April 2016
What is Vishing?
It is another variation of phishing. This uses a voice mail message to trick the user into calling the telephone
number contained in the message. As with all phishing attacks, the user will be asked to supply personal data
thinking they are talking to a legitimate company.
What is Pharming?
It’s a fraudulent practice in which a malicious code is installed on a user’s computer or on a web server. The code
will redirect the user to a fake website without their knowledge. It can lead to fraud or identity theft as the creator
gains personal data of the user such as credit/debit card details. Users can prevent pharming by using anti-
spyware software which can identify and remove pharming code.
What is spyware and key-logging software?
This is software that gathers data by monitoring key presses on the user’s keyboard; the gathered data is then
sent back to the person who sent the software. Spyware gives the originator access to all data entered using a
keyboard on the user’s computer.Anti spyware software can prevent this.
What is a virus?
It’s a piece of programming code which replicates itself with the intention of deleting or corrupting files on the
computer; they often cause the computer to malfunction. It can be prevented by using antivirus software.
What is a spam?
Spam is often referred as junk email. It is usually sent out to a recipient who is on a mailing list or mailing group.
Spam emails can lead to denial of services by clogging up the bandwidth on the internet.
What are the effects of spam emails on an organization?
 It clogs up the inbox or spam folder which is annoying.
 If a company uses email marketing then their emails can land up in the spam folders of the customers and
can never get viewed.
 For the email sender, their email will never get read by the customers thinking that it’s spam email.
 Waste of bandwidth for the sender and the receiver
 Customers can get irritated
 System can slow down and some mails can contain viruses.
What are moderated forums?
A moderated forum refers to an online discussion forum in which all the posts are checked by an administrator
before they are allowed to be posted.
What are cookies?
Cookies are small files or code that is stored on a user’s computer. They are sent by a web server to a user’s
computer. Once the cookie has been read by the code on the web server or user’s computer , the data can be
retrieved and used to customise the web page for each individual.
What are firewalls?
A firewall can be either software or hardware. It sits between the user’s computer and an external network and
filters information coming in and out of the user’s computer.