IGCSE Computer Science

all the key concepts and keywords

uses of hexadecimal

• IP addersses

• error messages/ codes

• assembly language // low-level language

• URL // web address

• memory dumps

• locations in memory

HTML structure [2 marks]

1. layout of the web page

2. e.g. where the text is placed

HTML presentation [2 marks]

1. formatting of the web page

2. e.g. colour of the font

Explain why presentation is often separated from structure when creating a web page. [2 marks]

1. formatting of the page can be changed/ edited without needing to alter the structure

2. … can make regular updates without needing to check the strucutre

3. formatting document can be used again for a different website

4. if further content and web pages are added —> the necessary formatting can easily applied…

5. …can save time when developing/ updating a website

browser

software/ application that allows the user to view web pages/ render HTML

Internet Service Provider (ISP)

company that provides a user with a connection to the Internet

HTTP/ HTTPS

protocol that is used to send data for web pages across the Internet

Uniform Resource Locator (URL)

made up of the protocol, domain name, web page/ file name; text-based version of a web address

cookie

a text file stored by the web browser that contains data about a user’s browsing habits/ details/ prefernces

firewall

hardware or software-based that prevents unwanted traffic from entering by filtering requests to ensure they are legitimate; monitors incoming and outgoing traffic and uses a set of rules to determine which traffic to allow.

hardware firewalls

will protect the whole network and prevent unauthorised traffic

software firewalls

will protect the individual devices on the network, monitoring the data going to and from each computer

high-level language

1. uses English-like statements

2. needs to be converted into machine code to be processed by a computer

3. … using a translator

4. one line of code can perform multiple commands

5. portable

freeware drawbacks

1. user is not allowed access to the source code…

2. …so, they cannot tailor the software to their needs

3. …so, they cannot fix any bugs in it

4. the software is still covered by copyright

5. user must get the owner’s permission to do anything beyond using it

freeware

• software available for free use

• but source code is not necessarily made public

• users can download and use the software without charge

• users cannot modify or redistribute the code

• protected under copyright

free software

• software users can access and use without paying a fee

• source code is publicly available for review, modification, and distribution 

free software benefits

1. user can access the source code…

2. …so, they can tailor the software to their needs

3. …so, they can fix any bugs in it

4. …so, the source code could be studied for educational pruposes

5. user can redistribute the software/ program…

6. …but this must be done under the same terms as the original software

phishing

1. email is sent to the user to encourage them to click link

2. …that takes the user to a fake website

think phishing → fish → hook → get them to click a link → has to be through email

pharming

1. email is sent to suer to encourage them to click link/ download attachment

2. …that triggers the download of malicious code of virus/ malware

think pharming → farming → dirty animals → harbour diseases → malicious tumours

security methods

• anti-malware software // anti-virus

• encryption

• password

• two step/ two-factor authentication/verification

• biometric device

• proxy-server

power surge - solution

use a UPS

water can be spilled on the device - solution

• don’t have water near the device

• keep device in a waterproof box when not in use

data is accidentally deleted - solution

• add verification method for data deletion

• set access levels for data to limit who can delete the data

fire can destroy device - solutions

• use electrics safety

• keep device in a fireproof box when not in use

incorrect use of storage device

making sure the device is ejected before removing

physical damage to hardware // hardware failure - solution

correct care and maintenance of hardware

software failure

making sure it is always up to date // enable automatic updates

optical data storage

= a method of storing data onto a disk-like medium; e.g. CD, DVD, Blu-ray

• uses lasers to read and write data

• uses a read/ write head

• burns pits into a reflective sensor

• stores data in tracks

magnetic storage

= a type of non-volatile media that uses magnets (polarity) to store binary 0s and 1s

• made up of several metal discs coated with a magnetic material called platters

• iron particles on each platter are magnetised to represent a 0 or 1

• uses a read/ write head

• stores data in tracks and sectors

solid state memory

= method of data storage with NO moving parts and uses NAND and NOR technology

shareware

1. trial version of software

2. …for a limited time/ number of uses

3. …with limited features

4. …free of charge

5. if full version is required need to pay fee/ sign up // when trial is over the user is asked to pay / sign up

6. protected by copyright

7. type of software licence

ethical issues when developing and distributing software

• copyright

• plagiarism

• production/ distribution of malware

• intellectual property of theft

• privacy of data

• age appropriation

• offensive materials

• environmental impact of distribution media (CDs)

• accessibility of software

• security of software

• following guidelines of professional bodies (ACM, IEEE, BCS)