Processing Knowledge and

1/28/2019 Information Technology (9626) - AS Level Notes - Google Docs

https://docs.google.com/document/d/1PrwcSBoW7p7qANn0iXDRVfjUFKBgUn0egTluWDTenN8/edit#heading=h.ffr5ksm47pzq 1/48

Data, Information, Knowledge and

Processing

Data, Information and Knowledge Data: Raw numbers, letters, symbols, sounds or images without meaning or context. Information: Data with context and meaning. Knowledge: Information to which human experience has been applied.

Sources of Data Static Data: Data that does not normally change. Dynamic Data: Data that changes automatically without user intervention. Primary Data: Data that is collected for the purpose for which it will be used. Secondary Data: Data that was collected for a different purpose.



Quality of Information Accuracy Data must be accurate to be considered of a good quality

Relevance Information must be relevant to its purpose

Age Information must be kept up to date in order to be useful

Level of Detail Too much information will make it difficult to find the information required. Too little information means that it cannot be used correctly.

Completeness All of the information required must be provided.

Coding and Encoding Data Advantages and Disadvantages of Coding Data

Advantages Disadvantages

Data can be presented in small spaces, and less storage space is required.

There may not be enough codes available to use, meaning that more letters or numbers need to be added.

Data can be input more quickly. Inputting data too quickly may result in errors.

Processors can process data more quickly since they only have to process the coded data.

Some letters such as O and 0 can be hard to distinguish, especially if handwritten.

Coded data can be validated by checking its length and/or its format.

If a user inputting codes does not know what code to use, then they will be unable to enter the data efficiently.

Data can be coded so that it cannot be understood by others.

Some information and detail may be lost in the process of coding.



Encoding Data When data is encoded, it is stored in a specific format. Computers use binary digits, which are 1s and 0s. Text is encoded as a number which is then represented by a binary number. The most common encoding method is ASCII (American Standard Code for Information Interchange), which consists of 256 codes from 0 to 255. Images are encoded as bitmaps. The pixel size of the image, the bit count, compression type and resolution is encoded. Sound is encoded by including information about the sample rate, the bit depth, and the number of channels. Lossy compression will reduce file size and reduce quality at the same time, while lossless compression reduces the file size without losing any quality. Video is encoded by storing both image and sound. Images are stored as frames, and a FPS value (frames per second) must also be determined. The resolution of the video and the bit rate is also encoded. Advantages

● Reduces file size, leading to smoother streaming and downloading. ● Reduced file size means that more files can be stored. ● Different file formats can be used for different purposes.

Disadvantages ● Required codecs may not be installed. ● Not all software is capable of opening different file types. ● Quality is lost when using lossy compression.



Encryption Encryption scrambles data so that if it is found, it cannot be understood. However, this does not stop the data from being intercepted, stolen or lost. As long as the encryption key or keys are kept secure, it is virtually impossible for somebody to decrypt the data using brute-force methods. Caesar Cipher A cipher is a secret way of writing. It is usually applied by shifting the letters of the alphabet along. This was used in the Roman Empire by Julius Caesar to communicate in secret with his generals. Symmetric Encryption It requires both the sender and recipient to possess the same encryption key, which is used to encrypt and decrypt the message. The secret key must be sent to the recipient, either alongside the message or separately. This isn’t very secure as both the message and the key could be compromised at the same time. Asymmetric Encryption This is also known as public-key cryptography. It helps overcome the problem of keys being intercepted by using a pair of keys. Each person possess a public key and private key. The public key is known to everyone, and is used to encrypt the message. The encrypted message is then sent to the recipient, and only they can decrypt the message by using the corresponding private key. This means that even if the message is intercepted, it cannot be read since the attacker does not have the corresponding private key. Digital certificates are used to list public keys, which list the public key itself, the certificate issuer, organisation name, and



the user’s details. However, constant encryption and decryption will slow down the transmission of information.

HTTPS Normal web pages transmitted using HTTP are not encrypted, meaning that attackers can easily read the data being received and transmitted. HTTPS adds a layer of security, usually Secure Sockets Layer (SSL) or Transport Layer Security (TLS) to encrypt and decrypt pages and information sent and received by web users. When a browser connects to a secure page, it will check if the digital certificate is valid. If it is, the browser will use the corresponding public to encrypt a new symmetric key, sent to the server. All communication is then encrypted using the new symmetric key, which is much quicker than asymmetric encryption. Hard Disks Disk encryption will encrypt every single bit of data stored on a disk. This means that even if someone gets physical access to the disk, they still cannot read the data since the encryption key will still be required. This is especially important for portable devices like USBs, since they are the most vulnerable to be stolen. Email Email encryption uses asymmetric encryption. Before encrypted emails can be sent and received, both the sender and recipient must send each other a digitally signed message containing their public key. The most common form of email encryption is known as PGP (Pretty Good Privacy).



Validation Validation takes place when data is input into a computer system. The data is checked to ensure that it has been entered correctly, and that it makes sense. If it isn’t, the user will be informed and they will be prevented from entering the data incorrectly. However, it is important to note that validation cannot check that the data itself is correct; it can only check that it has been entered correctly.

Presence Check

A presence check is used to ensure that data is entered, and that a field isn’t left blank.

Range Check

A range check ensures that data is within a defined range. This can be implemented by either using one boundary or two boundaries.

Type Check A type check ensures data is in the correct data type.

Length Check

A length check ensures data is of a correct range or within a range of lengths.

Format Check

A format check ensures that data matches a specific format. In databases, this is implemented as an input mask. A common example is for emails; they must follow the format [email protected]

Lookup Check

A lookup check tests to see if the inputted data corresponds to an option on a list. This is similar to referential integrity.

Consistency Check

A consistency check compares data in one field to existing data in another field to ensure that it is consistent.

Check Digit A check digit is a number or letter added at the end of an identification number. This character is calculated based on the rest of the previous numbers according to a specific algorithm.



Verification Verification is the process of checking that the data entered into a computer system matches the data from the original source. Visual Checking A user can look and read the data to ensure that the entered data matches the original source. This does not ensure that the original data is correct; it only ensures that the data has been copied and entered correctly. Double Data Entry This is where data is input twice, and the data is compared by the computer system to ensure that they match. If there are any differences, it means that one of the inputs must have been incorrect. However, if a user enters the data incorrectly twice in the same manner, the data will still be wrong but it will be verified. Proofreading Proofreading is where a person re-reads the input data to ensure that it makes sense. This is usually carried out using a person other than the one that did the data entry, since they will be able to spot errors more quickly. For large pieces of text, it may also be a good idea to proofread using spellcheck and grammar software, or printing the document out and reading it over line by line.



Hardware and Software

Hardware Hardware: A physical component of a computer system. Device: A hardware component of a computer system consisting of electronic components. Input Device: A device that allows data to be entered into a computer system. Output Device: Device used to communicate data or information from a computer system. Storage Device: A device used to store data onto a storage medium. Volatile: Data is lost when power is lost. Non-Volatile: Data is not lost when power is lost. Internal Hardware Devices CPU: Central Processing Unit. Performs calculations, logical operations, and fetches instructions from memory and executes them. They take inputs and convert them into outputs. CPUs usually consist of multiple cores, to allow multiple functions/calculations to be executed simultaneously. Motherboard: A printed circuit board which connects the main components of a computer. Other hardware components are connected directly to the motherboard.



RAM: Random Access Memory. It is volatile memory used to store currently active programs and data. Its extremely high speeds mean that programs and software can open and operate in real-time, without having to wait for data being written to/read off a disk. ROM: Read-Only Memory. It is memory that can only be written to once - it is permanent and non-volatile. These can usually be found on a motherboard containing the BIOS, or on small electronic devices like calculators. Graphics Card: A printed circuit board that generates the signals needed to output an image from the computer. Sometimes, it can be found as part of a CPU or as part of the motherboard. Powerful graphic cards are used for gaming, modelling, and simulations, since they contain hundreds of powerful processing cores. Sound Card: A printed circuit board that generates the signals needed to output sound from the computer to speakers or headphones. Nowadays, they are usually integrated into the motherboard, but higher-quality ones can also be purchased separately. External Hardware Devices Cloud: Cloud computing refers to anything where computing services are hosted over the internet and not the same physical location as the computer being accessed. When data is stored in the cloud, the hosting company takes all responsibility for storing and managing the data. The data can be accessed remotely from a variety of devices, but will usually be more expensive than physical storage methods.



Monitor: An essential part of most computer systems. Connected to the computer using a graphics card, and displays the graphical user interface. Monitors come in many different resolutions, and recent innovations have also made curved monitors possible. Touch-sensitive monitors also exist; these are known as touch screens. Keyboard: A number of buttons used to input text or control parts of an interface. In most languages, each key will correspond to a specific letter. Mouse: A pointing device which allows objects to be selected and manipulated on the screen. The mouse controls a pointer known as a cursor, which moves according to the movement of the actual mouse. Speakers: They provide sound output from a computer. Camera: Used to capture still or moving images. A higher-resolution camera will capture higher-resolution media. Expensive cameras also include image stabilization technology, where shaky footage is stabilized to make videos smoother. This is usually found in handheld devices. Webcam: A camera used for the purpose of capturing images while using the computer. This is usually lower-quality, and may also contain an integrated microphone. Usually used for video conferences. Microphone: A device which records sound and stores it digitally.



Printer: A devices which produces a hard copy from a computer, usually onto paper. There are four main types:

● Laser Printer. It negatively changes a cylindrical drum which attracts toner (powdered ink). The toner is the heated so that it melts onto the paper.

● Inkjet Printer. It uses four coloured ink cartridges (black, cyan, magenta, yellow) and squirts small droplets of ink onto a piece of paper.

● Dot Matrix Printer. These were popular in the past, and used physical pins to push ink on a ‘ribbon’ onto a sheet of paper.

● Plotter. A large inkjet printer designed for large sheets of paper, usually A2, A1 and A0.

Laser Inkjet Dot Matrix Plotter

Fastest of all printers. Standard speeds for home use.

Very slow. Very slow, since print area is very large.

Black and White Laser printers are the same cost as coloured inkjet printers. Coloured laser printers are very expensive.

Cheapest of all printers.

Cheap in the past, but they are now expensive since they are no longer mass produced.

Most expensive because of their large size.

Toner cartridges are more expensive than inkjet cartridges, but they last longer and the cost per page is actually less.

Ink cartridges vary in price, but a complete pack will often cost as much as the printer itself. ‘Compatible’ cartridges can also be purchased for cheaper.

Very cheap, as the ribbon lasts for a long time.

Same as inkjet printers, but much more expensive since the paper used is much larger and more ink is needed.



Usually black and white only. Coloured ones are more expensive.

Almost all inkjet printers print in colour.

Coloured ones are very rare.

Can print in colour.

Highest quality of all printers.

Reasonably good quality,but ink can show through thin paper and smudges may occur.

Usually poor. Same as inkjet printers.

Letters, bulk printing, general office and home printing.

Photographs, charts, general office and home printing.

Invoices or receipts requiring duplicates, ATMs, POS systems, hot and dusty environments.

Architectural drawings, large maps, canvas prints, posters.

Scanner: Used to capture documents in the form of an image. They perform a function similar to digital cameras, but at a much higher quality. Optical Character Reader: Also known as OCR. A device that enables characters on a document (usually a scan or a picture) to be identified and understood by a computer as actual characters. This is usually found in the form of a scanner with OCR software, where the scanned document is automatically converted into an editable document, and not a picture. Optical Mark Reader: Also known as OMR. Detects the marks that are made on a multiple choice document. A scanner-like device scans the paper, and translates the position of the marks into the data that is represented. Magnetic Ink Character Reader: Also known as MICR. Reads characters printed in magnetic ink, usually at the bottom of cheques.



Barcode Reader: Used to detect the width of lines and gaps that form a barcode. A laser beam is shined on to the barcode, and the reflected light indicates the presence of a white gap while absence of reflected light represents black gaps. Pendrive/USB Drive: A small data storage device about the size of a thumb which stores data on flash memory. The use of the USB interface means that it can be used on virtually all computers. The lack of moving parts means that it is very safe to transport. Portable Hard Disk Drive: This can be an external SSD or HDD, usually with a USB port for ease of access. They are usually found in rigid enclosures to protect them from drops and magnetic interference. Memory Card: Flash memory on a small card. Typically used in digital cameras and mobile phones. They are physically very small and can have a considerable amount of storage space, making them suitable for portable devices. Storage Devices Magnetic Tape Drive: Magnetic tape is used for backing up and archiving data. The low cost and high capacity of tapes makes them ideal for this purpose. However, data is stored sequentially since data is written as the tape is wound through the drive. This means that it will take a long time for a specific file to be retrieved, making it unsuitable for everyday use. Tapes are only ideal for backing up an entire system or all of the secondary storage for a computer or server since they can hold several terabytes of data. Optical Storage: This includes CDs, DVDs and Blu-Ray Discs. They are usually used to distribute music, films, videos and software.



HDD: Hard Disk Drive. The most common form of secondary storage. It is composed of multiple disks with a head that can read and write data to it. However, they are usually slow since data has to be physically written and read to the disk. Hard Disks are non-volatile forms of data storage. SSD: Solid State Drive. Also a secondary form of storage, but contains flash chips and no moving parts. They are also non-magnetic, meaning that they are safe from drops and magnetic interference. The lack of moving parts means that they are very fast, but also relatively more expensive. SSDs are usually used to store the operating system and frequently used programs for faster load times.

System, Application and User Interface Software: Programs which give instructions to the computer. User Interface: Method of communication between the user and the computers system. System Software System software consists of programs designed of programs intended to maintain or operate the computer system. Operating Systems: Software that manages the hardware within a computer system. It sits between hardware and applications software and manages communication between the two, and it allocates memory and transmits data connected to the computer system. Device Drivers: This is software that comes with external hardware components, designed to allow the operating system communicated with the device.



Application Software Programs that are intended for productivity or to carry ut a task for the user are known as application software. Word Processors: As their name suggests, they process words. They are suitable for writing large pieces of text and for mail merging. They often include features for tables, headers, footers, and a variety of formatting options. Spreadsheets: This is used mainly for performing calculations and modelling, often for financial and statistical information. Database Management Systems: These are used for viewing and editing data within a database, which is a structured collection of data in the form of tables which are related to each other. It will contain features such as data entry forms, filters, queries, graphs and security features. Graphics Manipulation Software: They contain features for manipulating bitmap and vectors. Using graphics manipulation software requires a lot of skill and advanced features are usually more appropriate for serious artists. Photo Editing Software: A specific type of graphics manipulation software focused on editing photographs. Home users can use it to make minor changes, while photographers can use it to enhance their photos. Video Editing Software: This is used to edit videos by merging and separating videos, adding transitions and animations, overlaying videos with text or images, etc. Communications Software: This can cover a range of tasks including instant messaging, audio conferencing, video conferencing and email.



Web Authoring Software: A type of software used for the creation and editing of websites. They can be very hard to use, but many provide previews of the webpage for the developer. Control and Measuring Software: Control software is used for controlling devices that are not part of the computer system, while measuring software is used to measure values in the real world. Apps: Another name for a program. It is a piece of software that can run on a desktop computer, over the internet, table computer or on a mobile phone. The most common reference to ‘apps’ is when referring to software designed to work with mobile phones. Applets: An applet is a small program designed to carry out a specific task. It cannot run on its own but must be executed from within another piece of software.

Utility Software Utility Software: Software that performs some sort of maintenance on the computer system. Anti-Virus: Also known as anti-malware software, they deal with malicious programs and threats to a computer system. They usually consist of a real-time monitor which constantly checks for malicious programs, and prevents them from being executed. The other part is a scanner which allows the user to scan the system for any existing viruses on malware, and remove/disinfect the computer as necessary. Backup: Backup utilities create a second copy of data and programs that are in storage. This can be set up so that automatic, regular backups are made.



Data Compression: These utilities will reduce the original size of files so that they use up less storage space. Opening compressed files will take longer, but they will also use up less storage. Disk Defragmentation: As a hard disk gets used, files are stored over all the magnetic platters in the hard disk itself. This can slow down file read/write times since the platters need to constantly spin round to locate the file or parts of the file, and new files may have to be broken up and written to several locations since there may not be enough available space. Disk defragmentation software orders the files and puts them close together, removing all gaps and speeds up file read and write times. This can only be used on HDDs. Formatting: Formatting is the process of organising the tracks/platters on a disk into sectors, ready for data to be stored. New drives will have to be formatted before use, and existing drives can be formatted to erase all the data on it.

User Interfaces Command Line Interface A command line interface (CLI) allows a user to enter text commands to which the computer system will respond. The computer system will output the result in a text format. CLIs use very little memory as there is no need to store any graphics, so they are useful in old systems and the maintenance of very small devices. However, they can be difficult to learn and use since users must memorise all the commands, and errors are easily made when entering those commands.



Graphical User Interface A graphical user interface (GUI) is the most common type of interface. All GUIs contain WIMP - which are windows, icons, menus and pointers respectively. Complex GUIs require a lot of memory to operate, but they are intuitive and very easy to use. Dialogue Interface This is where the user speaks to communicate with a computer system. A user can give commands using their voice and the computer system will give feedback using a synthesised voice. This is usually used in phone assistants and in-car entertainment systems. A big advantage of dialogue interfaces is that no hands are required, and they can be operated quite easily. However, the main problem with these systems is the quality of speech recognition, which may cause commands to be interpreted incorrectly. Gesture-Based Interface Gesture-based interfaces will recognise human motion, by tracking eyes and lips, identifying hand signals or monitoring whole body movement. This can be in the form of the user physically moving their hand (like in many game consoles), swiping on a touch screen, or even by tracking eye movement.

Custom-written/Off-the-shelf Software Custom-written: Software that is written specifically to meet the requirements of a client. Off-the-shelf: General purpose software available to a large market. When a client requires a software solution with specific purposes unique to their organisation, they will ask for software to be written for them. When software already exists and is purchased online or from a shop, it is known as off-the-shelf software.



Custom-Written Software Off-the-shelf Software

The entire development cost of the software is paid by a single client, which means that it could be quite expensive.

The development cost is spread between all the customers that purchase the software, making the cost significantly lower.

Custom-written software takes a long time to develop.

Off-the-shelf software is immediately available.

The requirements of the client can be met accurately without any redundant features.

Some needed features may be missing and there may be a lot of redundant features.

The developers will ensure that the custom software is compatible with the hardware, software and data used by the client.

There may be incompatibility issues and bugs, making updates necessary.

The client will have direct support from the company that developed the software.

Customers will be able to get support from the developers, discussion forums and online training.

Compilers and Interpreters Compilers Compilers translate software written in a high-level programming language into machine code which a computer can understand. The whole source code is translated into an executable at once. The executable file does not have any dependencies, and can be run as a standalone program. A compiler is capable of identifying all the errors in a program after it has been compiled, and it can optimise code to run as efficiently as possible.



Interpreters Interpreters also translate a program written in a high-level programming language into machine code, but it does so one line at a time. This can be less efficient since it takes time. However, interpreters are useful for testing since errors are reported on a per line basis, so they can be easily identified. Source code that has not been compiled into an executable file will need an interpreter to run, with every few lines being fed into memory and executed at once. Linkers Linkers (also known as link editors) combine several modules, separated into object files, into a single executable file. The object files are also known as dependencies, as they are necessary for the program to run. Programs also often use a common library, which contains basic functions such as mathematical operations, memory management, progress bars and input/output features. Compiler VS Interpreter

Compiler Interpreter

Translates source code into machine code all at once before execution.

Translates source code into machine code one line at a time.

Compiled code will only work on the operating system it was compiled for.

Source code can be translated in real time into machine code for any operating system.

Machine code is ready to be executed without delay.

Machine code has to be translated first, so additional time is added to the execution time.

Compiling can take a long time, which is not appropriate for on-the-fly testing.

Only the required code needs to be interpreted, so this is efficient for on-the-fly testing.



Monitoring and Control

Sensors Sensor: A device that record data about the surrounding physical environment. Analogue: A smooth stream of data that we process on a daily basis. Microprocessor: An integrated circuit used in monitoring and control technologies. Actuator: A type of motor that controls a mechanism or system. Sensors can automatically enter data into a computer system, making them extremely useful for automation, and in environments that could be harmful to humans. A sensor constantly monitors the surrounding environment, and the data it records will be in analogue form. An analogue to digital converter must be used to convert the data into digital form, which is then sent to a microprocessor. If the data is in an acceptable range, the microprocessor will signal the actuator to trigger an action that needs to be taken. Motion Sensors Motion sensors detect movement. This can either be passive or active; an active sensor is usually an infrared sensor, and detects any changes in energy in the surrounding environment. An active sensor is usually a microwave sensor, which constantly emits microwaves and detects changes in the reflection of the waves, much like a bat. However, motion sensors are not error proof, and sometimes may trigger a false alarm or not



trigger at all when there is actual movement. These sensors are usually used in CCTV systems, and automatic doors and lights. Pressure Sensors A pressure sensor measures pressure, usually of a liquid or a gas. Most pressure sensors use piezoresistance, where a specific level of pressure is linked to a specific level of charge. They are frequently used in the manufacturing of vehicles and chemicals, and also in touch screens. Moisture and Humidity Sensors Humidity sensors monitor the humidity in the air. They use two electrical conductors with a non-conductive film separating them. Moisture collects on the film and changes the level of voltage between the two conductors, which is then interpreted as a measurement of humidity. They are used in wine cellars, meteorological stations and in agriculture. Temperature Sensors They monitor and measure the temperature of an environment by measuring how much heat is present. They are found in many home appliances. Light Sensors There are many different types, but the most common type uses photoresistors. These resistors will change its resistance depending on the light shining on it. They are used in digital cameras, scanners and smartphones.



E-Safety and Health and Safety

E-Safety Phishing This is when an unauthorised person tries to gather personal data by disguising or impersonating a trustworthy person or organisation. This is usually done in the form of phishing emails which try to trick a user into logging in to a fake phishing website, which looks like a legitimate website but is designed to steal the user’s login credentials or private information. Pharming This is another method of collecting personal data by installing malicious code onto a computer or server. When a user attempts to access a legitimate website, they will be redirected to a fake phishing website. This can be done by hijacking the user’s DNS server, which maps domains to IP addresses. It can also be done by changing the ‘hosts’ file on the user’s computer; this file overrides DNS settings. Smishing This is SMS phishing. It may try to trick a user into accessing a phishing website or phoning a fake number. Vishing This is vishing over voice, where a fraudster calls a user and claims to be from a certain organisation requesting personal information. They will often



impersonate a bank and claim that there are fraudulent charges on the user’s account. The victims of this are usually elderly or vulnerable.

Malware Trojan Horse This is a malicious program which disguises itself as useful software. When the application is run, the trojan horse will execute in the background, usually to install other malware. Worms A type of malware that exploits holes in computer networks to replicate itself and quickly spread through the network. This is usually done to install other malware once the worm is in place. Spyware This refers to any software that is used to gather data about a person without their knowledge. Keyloggers are the most common type of spyware; they will record all the actions performed by a user, including all keystrokes. Adware This is software used to display adverts targeted at the user. Adware will usually fill the user’s screen with adverts in the form of popups or windows. Adware is often bundled with free software. Rootkit This is a type of malware that enables a person to gain administrator access to a victim’s computer. This access can be used to disable any safety mechanisms, such as firewalls or antivirus software.



Malicious Bots Bots are applications that are programmed to repeatedly carry out certain tasks. These are usually used by cybercriminals to bombard people with spam emails. Bots can also be used on instant messaging services to try and trick users. Infected computers can also be turned into ‘zombie bots’, which are used to collectively launch attacks on websites. Ransomware A type of malware which encrypts all of the user’s files and demands a payment for decryption. Usually, the only method for the user to recover their files is to pay, often using cryptocurrencies.

Health and Safety Health Issues RSI (Repetitive Strain Injury): This is pain, numbness or weakness that occurs in the hands, arms, shoulders and the neck. This is caused by repetitive movements such as typing or clicking and poor posture. To prevent this, a good posture should be maintained and regular breaks should be taken. Wrist rests can also be used to support a user’s wrists. Carpal Tunnel Syndrome: Pain and numbness in a user’s hands and fingers. It is cause by the compression of a major nerve, and happens because of constant repetitive movements. Again, users should take regular breaks to avoid this. Back Pain and Muscle Spasms: Caused by poor posture. A user should sit on an adjustable chair with proper back support. Eye Strain: A user will often experience eye strain when looking at a monitor for extended periods of time. Users should configure their monitor correctly to reduce this, and they should take regular breaks.



Deep Vein Thrombosis: This is when blood clots occur, usually in the legs. This is normally caused by sitting in a chair that puts pressure on the back of a user’s legs, mostly behind their knees. This can be prevented by taking breaks and standing up for a while. Fatigue: This is when a user gets very tired from overworking for long continuous periods of time. Users should take regular breaks. Safety Issues Fire: Computers can overheat and could cause fires. This can also occur because of overloaded plug sockets. Computers should be used in rooms that are properly ventilated, with fire extinguishers nearby. Plug sockets should not have too many devices plugged into them, especially those that require a lot of power. Loose Wires: There can be trailing wires, especially when plug sockets are not near computer systems. A person could trip over these wires. Wires should be secured by cable management systems or they should simply be clipped together to prevent this. Spilt Drinks: These can cause a short in a computer. Eating and drinking at a computer should be avoided where possible. Electric Shock: This can occur if a user touches wires, especially if they are worn out. It can also occur if liquids are spilt onto an electrical device. Caution should be taken when handling electrical wires, and old ones should be repaired. Liquids should be kept away from electrical devices.



The Digital Divide The Digital Divide The digital divide describes the technology gap between countries, demographic groups and economic areas. The divide that people can experience depends on many factors, including age, status and location. The digital divide isn’t just limited to internet access; iit includes other forms of modern technology, including telephones, television, computers, and home appliances.

Causes Location A person’s geographical location can have an effect on their access to technology. There is a digital divide between those living in rural areas and those living in urban areas, since urban areas already have most of the infrastructure in place to provide high-speed broadband services. There is also a higher concentration of people, meaning that ISPs have a large incentive to develop broadband in the area. Rural areas are sparsely populated, so ISPs are reluctant to develop broadband in these locations. There is also a global digital divide caused by the location factor. The quality and price of internet connections can differ dramatically from country to country, which can affect the adoption of technology. Developed countries usually have high-speed, affordable connections, while developing countries usually don’t. This is usually because less developed countries allocate more financial resources to other services and there isn’t enough to concentrate on developing technology services.



Developing countries may find themselves stuck in a vicious cycle; the lack of technology means that they cannot trade using modern technologies and cannot access the same customer base. This will also affect the level of education since they won’t have access to the internet as an educational resource. These consequences could prevent a country from developing further and competing on an international level. Income There is a digital divide between economic classes, since richer people are able to afford access to high-speed internet connections and expensive devices. Poorer members of society may be unable to afford these services, which could have an impact on their level of education and ecommerce, creating a greater divide. An increasing number of companies are transacting online exclusively, and the inability to access the internet creates a significant divide between rich and poor people. Age The digital divide can exist between old and young people, since young people have grown up surrounded by technology and have become accustomed to it, while the elderly may be reluctant to learn how to operate modern devices. They may also have no use for modern technology.

Solutions ● Community teaching programmes to teach older people how to use

technology. ● Subsidising/gifting devices to children from poor backgrounds. ● Setting up cyber cafes in rural areas. ● Providing overseas aid to countries to purchase technology. ● Setting up affordable 4G connections in rural areas.



Using Networks Networking Computers Network: A set of computers and devices connected together so they can communicate and share resources. Network Architecture: The design of its network both geographically and physically. Local Area Networks (LANs) and Wide Area Networks (WANs) Local Area Network: A network that covers a small geographical area. They are usually found in homes, schools, universities and small businesses. Wide Area Network: A network that covers a large geographical area. This can be within a country or across the globe. The internet is an example of a global WAN. Several LANs can be connected together to form a WAN - this is usually the case for multinational companies.

Local Area Network Wide Area Network

Up to 1Gb per second. Usually restricted to less than 200Mb per second.

Few data transmission errors, as data packets sent over short distances.

Greater chance of error as packets are sent over longer distances.



Restricted to a small location. Copper wire, fibre optic cable or radio waves are mostly used.

Expanded to a wide location, with copper wire, fibre optical cable and microwaves being frequently used. They can often use public telephone systems, leased lines and satellite communication.

High security, as it is easier to implement over a smaller number of devices and connections.

Relatively low security, as it is difficult to implement across a larger number of devices and connections.

Usually owned by individuals or organisations.

Often uses infrastructure owned by others.

Client-server Network They used a dedicated server to store data, manage resources and control user access. The server acts as a central point on the network that other computers connect to. Computers that connect to the server to access the data and resources it manages is known as a client. A client-server network will usually have at least one server and several clients. Multiple servers can also be found in some network, in order to spread out the workload an ensure the network runs efficiently. Advantages:

● Centralised database of users and login credentials provides security. ● User data is kept private. ● Users do not need to make backups as they are centralised. ● Several servers can be used for different functions for efficiency.

Disadvantages:

● Expensive to set up and maintain. ● Single point of failure. ● Requires specialist technical staff to maintain.



Peer-to-peer Network Users store data on their own computer, but may allow other users to access it. They can also choose to not do so, but they can still connect to other peers. Advantages:

● Cheap to setup and maintain. Does not require expensive servers. ● Failure of an individual peer does not cause the entire network to stop

working. ● Does not require specialist technical staff to maintain.

Disadvantages:

● No centralised database of users and credentials, making it harder to maintain security.

● Users have to worry about backing up their own data since there is no centralised system.

● The more computers on a peer-to-peer network, the slower it will run. Virtual Private Networks (VPN) Companies or organisations may want to allow users to access a network, often a LAN, from a remote location. To ensure security, a virtual private network can be implemented. Once connected to the VPN, the remote computer has secure access to the LAN’s resources, as if it were directly connected to the LAN. This is done through a process called ‘tunneling’; the remote computer connects to the LAN directly via an encrypted tunnel to securely transmit data through a possibly unsafe network.



Advantages: ● They maintain a high level of security for data transmission over the

internet. ● VPNs use external resources. There is no need to purchase or

implement secure, dedicated connections called leased lines for users that wish to access the network.

● The cost of maintaining external resources is covered by someone else.

● Adding extra clients costs little to nothing as the network is virtual. Disadvantages:

● Performance of the VPN may be outside the control of the organisation, since it is dependent on the external resources that are used.

● A certain amount of technical expertise is needed to set up and maintain VPNs. This must be factored in when deciding whether to implement a VPN.

Intranets and Extranets Intranet: A privately owned network that uses internet technologies, such as web pages, for internal use within an organisation. They typically use client-server architecture, often with multiple servers. Extranet: An intranet that has been opened up to allow external user access. Extranets use VPNs to allow an external user to securely access the information on them. However, extranets usually only allow certain information of the intranet to be accessed.

The Internet The internet is a global network made up of interconnected network and individual computers. This global network allows users to access online services.



Characteristics To connect to the internet we need to use an internet service provider (ISP), which owns the infrastructure needed to connect to the internet. Data and information is held and distributed by content providers. Most devices connected to the internet act as clients, and the majority of data is held on web servers. There is no entity with centralised control, with various independent organisations controlling certain aspects of the internet. This means that the quality of information on the internet is mixed; it can be useful and correct, but it can also be completely incorrect. The internet is also constantly changing and evolving, with data being modified and more and more devices connecting to it every day. Benefits:

● There is a large amount of information available on any topic. ● Contributors have a global audience. ● Immediate transmission of information. ● Immediate availability of services. ● International ecommerce. ● Many options for entertainment. ● Free education, accessible to all. ● Social Networking. ● Real-time, up-to-date news. ● Lowered costs for businesses and organisations. ● Ease of providing feedback. ● Possibility of using big data to improve existing services.



Drawbacks: ● Incorrect, misleading information. ● Anonymity may lead to inappropriate behaviour. ● Hacking and viruses. ● Identity Theft. ● Inappropriate content is easily accessible. ● Online addiction, especially to social media and videogames.

The World Wide Web The internet describes the physical, global network, while the world wide web describes the information system running on the internet. Users access this information using a web browser.

Mobile Networks A mobile network is a wireless WAN that uses radio waves to transmit and receive communications from portable devices, such as smartphones. Mobile networks cover a considerable amount of the inhabited areas of the world. Advantages:

● Users can communicate with others while on the move, usually through the use of smartphones.

● The network is broken down into small areas called cells, which allows lower power radio transmitters to be used, bringing energy and cost savings.

● There is a limited number of radio frequencies available. These can be split among neighbouring cells and reused in more distant cells, increasing the number of possible simultaneous connections.

● Large areas can be covered using a single transmitter. ● Multiple transmitters ensures there is no single point of failure of the

entire network; if a cell fails, only a small area will be affected.



Disadvantages: ● Quality of reception can vary and can be poor at the edge of a cell. ● The frequencies used must be carefully planned to avoid interference

between cells. ● Setting up large mobile networks costs money, and may be

impractical in sparsely populated areas.

Video and Web Conferencing How to set up a video conference A video conference will require a desktop computer or laptop, a webcam, a microphone, a monitor, speakers, a stable network connection and video conferencing software. Smartphones can also be used. To initiate a video conference, the following steps must be followed:

● Register with the video conferencing service. ● Install the video conferencing software. ● Select another registered user and initiate a conference call.

The following should also be taken into account:

● Ensure that all participants have a stable internet connection. ● Ensure that microphones are inputting voice at a suitable level. ● Ensure that webcams are positioned correctly and that image quality

is acceptable.



How to set up a video conference This is similar to setting up a video conference. The steps are as follows:

● Send an invitation to interested participants, stating the time and date of the conference.

● Send access codes/login credentials and a link to the website with the invitation or separately.

● Login to the web conference service. ● Select an appropriate meeting space/room. ● Manage the web conference by disabling messaging/cameras/muting

other participants. Networks in Video and Web Conferencing Integrated Services Digital Network (ISDN): This is a networking technology that allows data to be transmitted digitally over analogue copper wire. It is quite slow and only used in areas where new technology has yet to be implemented. Asynchronous Digital Subscriber Lines (ADSL): This is also known as broadband, and is the most common type of connection to the internet. It is typically used in homes and businesses. Asynchronous means that download speeds do not match upload speeds. Synchronous Digital Subscriber Lines (SDSL): Same as ADSL, but with equal download and upload speeds. 3G/4G Mobile Networks: These are used, usually by smartphones, to allow users to join a video conference when travelling or when access to a LAN is not possible. Video conferencing software uses codecs to compress video and audio signals so that they can be transmitted more efficiently, especially in networks with low bandwidth. The data is decoded at its destination.



Impact The rise of technology and video conferencing means that users can see and hear their friends and family from far away easily. It has also enabled witnesses to give testimony via video conferencing, especially in the cases where witnesses may be too upset to attend court. Defendants can also make initial court appearances via video conferencing, reducing travel costs. Suspects and witnesses can also be interviewed via video conferencing. Video conferencing has also been used in education to engage students by allowing them to participate in discussions with other schools and universities. This has also made live debates and remote teaching possible. Experts can also give talks and lectures remotely. Consultants and physicians from different hospitals can also make use of video conferencing to discuss a patient’s case and help offer a diagnosis. External devices such as ultrasound scanners and video endoscopes can also be connected and shared with the video conference, improving medical care. Video conferencing can also be used for doctors and nurses to keep in touch with patients living in remote areas. Video conferencing has helped businesses by enabling meetings that do not have to be conducted face-to-face. This saves travel expenses and allows for more efficient use of an employee’s time. Teleworking is also possible, where employees can work from home while being less isolated from their employer and co-workers. Video conferencing can also be used for staff training. However, some people are less confident in front of a camera, and some employees may feel more stressed in virtual meetings than in face-to-face ones. In the news and media sector, video conferencing allows journalists to deliver live reports and report on international press conferences.



Expert Systems Components An expert system is a computerised system that tries to replicate human decision-making processes, usually experts. They are designed to try and reproduce the judgement of a human expert in a certain field. By doing so, they can be used to replace or assist a human expert. Expert systems gather data by asking the user questions about the problem. The questions asked will depend on the user’s responses. Expert systems are composed of three main components: the knowledge base, the inference engine and the user interface. Knowledge Base The knowledge base is a database which allows the storage and retrieval of knowledge provided by a collection of experts. This is collected by interviewing the experts and using the data obtained to build the knowledge base. The rules base is part of the knowledge base. The rules base contains a set of rules (if statements) which are used by the inference engine to obtain a solution to a problem or a decision. Inference Engine The inference engine is the part of the expert system which makes judgements and reasoning using the knowledge base and user responses. It produces reasoning based on a set of rules. It follows a line of logic based on the user’s answers to the questions it asks, often using a chaining method. The chaining method is the sequential process of following logic in order to reach a conclusion.



Chaining can be forward or backwards; forward chaining is where an input is provided and a conclusion is reached, while backward chaining is when a conclusion is known and the expert system works in reverse to find the path to it. User Interface The user interface is the way the user interacts with the expert system. The interface will allow the user to input their answers, and will output the conclusion that the expert system gives.

Uses Expert systems are usually used for the following purposes:

● Medical Diagnosis ● Car Mechanical Diagnosis ● Playing Chess ● Providing Financial Advice ● Troubleshooting computer and printer issues ● Identifying items, for example plants and birds

Data Processing Systems Batch Processing Systems A batch processing system is a system that processes batches of data at set time intervals. These collections of data are stored together in what is known as batches. By storing the data in batches, processing can be carried out when the system is in less demand. However, there is a time delay for data processing, so the output is not always readily available. Also, errors will only be recognised after the data is processed. Examples of batch processing systems include payroll and stock control systems.



Online Processing Systems Online processing systems usually deals with data in transactions. Transactions are small inputs of data, and once all the data of a transaction is collected, it is processed and the next transaction can occur. Examples include online booking systems. Real-time Processing Systems A real-time processing system processes data as soon as it has been input. They are normally used when data needs to be processed immediately. However, they require a lot of resources since the system needs to be ready to process data at a moment’s notice. Examples include air traffic control systems and real-time computer games. Master Files These are collection of fields about a main element of a data system, with its information being mostly permanent. Transaction Files These are files with temporary data used to update master files. In real-time and online processing systems, the transaction file is matched with the master file and is processed. In a batch processing system, the transaction files are stored until a suitable time to update the master files.



Spreadsheets

Definitions Formulae: A formula uses basic arithmetic calculations. Functions: A function is a ready-made formula representing a complex calculation on both numbers and text. Absolute Referencing: This is used when a cell reference shouldn’t change when the formula/function is copied to other cells. A $ symbol is used.

Functions

SUM Calculates the total of values within a range.

=SUM(A1:A10)

AVERAGE Calculates the average of values within a range.

=AVERAGE(A1:A10)

MINIMUM Calculates the smallest values within a range.

=MIN(A1:A10)

MAXIMUM Calculates the largest value within a range.

=MIN(A1:A10)

INTEGER Returns the whole number value of a decimal number.

=INT(A1)

ROUND Rounds a number to the nearest decimal place specified.

=ROUND(A1,2)

ROUNDUP Rounds a number up to the nearest decimal place specified.

=ROUNDUP(A1,2)



ROUNDDOWN Rounds a number down to the nearest decimal place specified.

=ROUNDDOWN(A1,2)

DAY Calculkates the day part of a date.

=DAY(A1)

MONTH Calculates the month part of a date.

=MONTH(A1)

YEAR Calculates the year part of a date.

=YEAR(A1)

DATE Calculates the date from a given year, month and day.

=DATE(A1,B1,C1)

HOUR Calculates the hours part of a time.

=HOUR(A1)

MINUTE Calculates the minutes part of a time.

=MINUTE(A1)

SECOND Calculates the seconds part of a time.

=SECOND(A1)

TIME Calculates the time from given hours, minutes and seconds.

=TIME(A1,B1,C1)

NOW Returns the current date and time.

=NOW()

CONCATENATE Joins together text values. =CONCATENATE(A1,B1,C1)

LEFT Extracts the furthest left characters.

=LEFT(A1,3)

RIGHT Extracts the furthest right characters.

=RIGHT(A1,3)

LEN Calculates the length of a string. =LEN(A1)

UPPER Converts text into upper case. =UPPER(A1)



LOWER Converts text into lower case. =LOWER(A1)

VLOOKUP Searches for a value in a table and returns a value from the same row.

=VLOOKUP(A1, B1:C4, FALSE)

HLOOKUP Searches for a value in a table and returns a value from the same column.

=HLOOKUP(A1, B1:C4, FALSE)

IF Executes one function or the other based on the value of a cell.

=IF(A1 = 1, “hi”, “bai”)

COUNTA Counts the number of cells that are not empty in a range.

=COUNTA(A1:A10)

COUNTIF Counts all values within a range that meets a certain criteria.

=COUNTA(A1:A10, “Yes”)

SUMIF Adds up all values within a range that meets a certain criteria.

=SUMIF(A1:A10, “>0”)

AVERAGEIF Calculates an average of all values within a range that meets a certain criteria.

=AVERAGEIF(A1:A10, “>0”)

Modelling A model is a computer representation of a real-world process, created using mathematical analysis. Spreadsheets can be used to create computerised models, but custom-written solutions are also used to model specific purposes. Models are usually used to train people to use equipment and for forecasting. Training employees using real-world equipment can be costly and dangerous, and changes should be tested in a model before applying them to the real world.



Simulations A simulation is the use of a computerised model to predict how a real-life system might behave. They are also used for training and forecasting. Typical simulations include natural disaster planning, pilot training, car driving and nuclear science research. Advantages:

● It is not necessary to create expensive prototypes or the real thing in order to experiment with different variations.

● Changes to the model can be made very quickly. ● Alternative models and designs can be easily implemented. ● Unusual events (e.g. earthquakes) can be tested without needing to

wait for them to actually happen. ● Equipment does not suffer from wear and tear and there is no risk of

damaging it during testing. ● Dangerous simulations can be tested without putting people in

danger. ● Simulations can be sped up so that the results from slow processes

can be obtained quickly. Disadvantages:

● The effectiveness and reliability of a simulation highly depends on the underlying model.

● Simulation software and equipment can be very expensive to purchase.

● Training is needed to use simulation equipment and software. ● Complex models can take years to develop, especially for

complicated processes. ● It is impossible for a simulation to be a perfect representation of the

real-world process.



Database and File Concepts

Relationships One-to-one A one-to-one relationship is when each record in one table only connects to one record in another table. Foreign keys will only link to one primary key and viceversa. One-to-many A one-to-many relationship is when each record in one table can connect to many (zero or more) records in another table. This is the most common type of relationship within relational databases. Many-to-many They are not used in relational databases as they are converted into two sets of one-to-many relationships. Technically, in a many-to-many relationship, each record in one table can connect to many records in another table but each record in the other table can also connect to many records in the original table.

Types of Databases Flat File This is a database that consists of a single table with no relationships, much like a single worksheet in a spreadsheet. This will usually lead to redundant data, which is data that is repeated and takes up storage space.



Relational Relational databases contain multiple related tables, which eliminates data redundancy.

Keys Primary Key A primary key is a unique identifier for each record in a table. The field used for the primary key must contain unique values, and its data must be permanent. Compound Key A compound key is two or more fields combined to form a unique identity. These should not be used in relational databases as they are very complex. Foreign Key A foreign key is a field in a table that refers to the primary key in another table. The foreign key must always have the same data type and field size as the primary key it is linking to. Referential Integrity Referential integrity exists when data in the foreign key on the many side of a relationship exists in the primary key of the table on the one side of a relationship. This means that a record can only be input if the key already exists in the other table; if it doesn’t, the database will prevent the data for being entered. This is important for maintaining the accuracy of data within a database.



Validation Lookup in list Gender “M” or “F”

Lookup in list Title IN(“Mr”,”Mrs”,”Miss”,”Dr”)

Range Date of Birth <DATE()

Range Date Joined >28/02/1995

Data Type/Format Initials Like “[A-Z][A-Z]”

Format Email Like “*@*.*”

Length Any two characters Like “??”

Presence Name IS NOT NULL

Data Dictionary A Data dictionary is a document or file that describes the structure of the data held within the database. It is known as metadata which means ‘data about data’. It includes the following:

● Field Names ● Data Types ● Field Size ● Format ● Default Values ● Primary keys, compound keys and foreign keys ● Indexed fields ● Validation rules ● Sort order ● Relationships



Management Information System (MIS) A Management Information System is used by managers to aid them in their managerial duties. They provide past, present and prediction information, which helps managers make informed decisions for their business. They will include many data resources, such as databases, and also the hardware resources of a system. They will include tools to easily produce reports and charts for sales, revenue and production data. Managers will be able to easily spot trends by comparing historical data or by looking at charts and graphs.

Processing Knowledge and

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