Theory Worksheet PDF

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A worksheet for IT 9626...

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Cambridge Internati International onal Exa Examinations minations AS ICT (9626)

Theory Workbook September 2016

Student Name:

Contents

Topic 1: Data, information, knowledge and pro processing cessing ............................................................................. 4 1.1 Data, information and knowledge .......................................................................................................................................................................4 1.2 Sources of data ...............................................................................................................................................................................................................4 1.3 Quality of information .............................................................................................................................................................................................. 10 1.4 Coding, encoding and encrypting data ........................................................................................................................................................11 1.5 Checking the accuracy of data ......................................................................................................................................................................... 24

Topic 2: Hardware and software ........................................................................................................................... 26 2.1 Hardware ............................................................................................................................................................................................................................ 26 2.2 System, application and user interface software .................................................................................................................................. 33 2.3 Utility software ............................................................................................................................................................................................................... 50 2.4 Custom written software and off-the-shelf software ........................................................................................................................... 52 2.5 Compiler and interpreter ........................................................................................................................................................................................ 53

Topic 3: Monitoring and control ........................................................................................................................... 56

Topic 4: E-safety and health and safety .......................................................................................................... 60

Topic 5 : The digital divide ..................................................................................................................................... 67

Topic 6: Using networks ............................................................................................................................................ 69 6.1 Network types ................................................................................................................................................................................................................. 69 6.2 Video and web conferencing ............................................................................................................................................................................... 78

Topic 7: Expert systems ............................................................................................................................................. 84

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Topic 1: Data, information, kknowledge nowledge and proc processing essing Week 1 – Lesson 1 1.1

Data, information an and d knowledge

• define dat data a, clearly identifying that data has no meaning …………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………………

• define info information rmation and show how data can become information through context and meaning …………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………………

• define kknowledge nowledge and Explain that information becomes knowledge when human experience is applied

………………… …………………………………… ………………… ……………………………………… …………………… ……………………………………………… ………………………… ……………………………………………… …………………… ………………………………………… …………………… …………………………………………… ……………………… ……………………………………… ……………… ………………………………………… ………………………… …………………………… … ………………… …………………………………… ………………… ……………………………………… …………………… ……………………………………………… ………………………… ……………………………………………… …………………… ………………………………………… …………………… …………………………………………… ……………………… …………………………… …… ………………………… …………………… ……………………………………… …………………

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Exam Practice Questions

Specimen - 2017

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1.2

Sources of data

1) Define sta static tic data and give an example

Static Info Information rmation So Sources urces - Advantages

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Static Info Information rmation So Sources urces - Disadv Disadvantages antages

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2) Define dy dynamic namic data and give an example

Dynamic IInformation nformation S Sources ources - Adv Advantages antages

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Dynamic IInformati nformati nformation on Sources - Disadvantages

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3) Define di direct rect data so source urce and explain the advantages and disadvantages of gathering data from direct data sources

Direct IInformation nformation So Sources urces - Advantages

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Direct IInformatio nformatio nformation n Sources - Disadv Disadvantages antages

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4) Define ind indirect irect data source and explain the advantages and disadvantages of gathering data from indirect data sources

Indirect Informatio Information n Sources - Adv Advantages antages

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Indirect Informatio Information n Sources - Dis Disadvantages advantages

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information 1.3 Quality of informati on • Explain how the following can affect the quality of information:

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Accuracy

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Relevance

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Age

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level of detail and completeness of the information

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1.4 Co ding, encoding an d encryptin g dat a Coding, and encrypting data • describe the coding of data (including: M for male, F for female) and more intricate codes (including: clothing type, sizes and colour of garment) Give examples of coded data: …………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………………

• discuss the advantages and disadvantages of the coding of data

Coding Data - Ad Advantages vantages

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Coding Da Data ta - Disadv Disadvantages antages

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• evaluate th the e need fo forr encoding dat data a It is common for much of the data collected and entered into a system to have some degree of repetition and redundancy i.e. extra information that does not add anything. And this pattern or repetition is why it is efficient to code the data in some way. Need 1: Sp Speeding eeding up data en entry try Let's take the example of collecting data about a person's gender. People can be either 'Male' or 'Female'. Whilst these two options are easily understood by all, imagine having to enter the word 'Male' and 'Female' into a system many hundreds of times. It is a waste of time and effort because no extra information is contained in the full words compared to a single letter. Need 2: IIncrease ncrease accu accuracy racy of data ent entry ry The other issue is that no matter how accurate a person is at data entry, at some stage they are likely to make a mistake and might spell 'Male' as 'Mail' or 'Female' as 'Femal'. This type of mistake will make any results from your database queries unreliable. Instead of entering 'Male' or 'Female' you could code the data and instead enter it as 'M' or 'F'. Simply having to enter one letter instead of a possible six will speed up data entry. It will also cut down on the risk of mistakes being made with spelling. Need 3: Us Use e of valid validation ation In our example, the words 'Male' or 'Female' have been coded so that they become 'M' or 'F'. When data has been coded it makes it easier to use validation to check if the data entered is sensible. With the example above, the person entering the data could still make a mistake and enter 'S' instead of 'M' or 'F'. But if you set up validation so that the field will only accept the letters 'M' or 'F' and absolutely nothing else then that should further cut down on possible mistakes. Note that validation can only check if the data is sensible and within reasonable limits, it cannot check whether the data is accurate. Somebody could still enter 'F' instead of 'M'. Need 4: Le Less ss storage sspace pace req required uired Every letter that you store in your database system will take at least one byte of storage. If you store 'Female' as 'F' then you will save five bytes of storage space. If the system belongs to a large organisation, there might be many thousands or millions of records stored - simply by coding one field, a huge amount of hard disk storage can be saved. Need 5: Faster searching for data It stands to reason that the smaller the size of your database, the faster it will be to search and produce results. Thus by coding data and keeping the size of the system to a minimum the more time you can save in the long run when running queries.

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Analyse the d different ifferent methods that c can an be used to encode data (i (including: ncluding: codecs) 

Analogue to Digital convertor

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Codecs

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Exam Ques Questions tions Practice

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• define encryption and describe different methods of encryption (including: symmetric, asymmetric, public key, private key)

Data Encryption:   

Symmetric Key Encryption (plain text, cypher text and use of a key) Asymmetric Key Encryption (plain text, cypher text and use of a private and public key) Cipher Encryption (Substitution and reposition)

Encryption is the process of converting information into a form that is meaningless to anyone except holders of a ‘key’.

What is plain text? In cryptography, plaintext is ordinary readable text before being encrypted into ciphertext or after being decrypted About Cyphers There are many types of ciphers developed over time. Most common ciphers involved some form or substitution or transposition of alphabetical letters. Substitution means to substitute one character for another while transposition is some form of repositioning characters within the message (which literally scrambles the information). In the digital age, ciphers changed and are generally based on two types of algorithms--one using the same key to encrypt and decrypt (symmetric encryption), and one using different keys to encrypt and decrypt (asymmetric encryption). The one that uses symmetric keys falls under private-key cryptography, while asymmetric key algorithms falls under public-key cryptography.

Example of symmetric encryption also known as private-key cryptography

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First Alice needs to generate a secret ‘key’ using encryption software. The key is usually a very long, random number.

Alice must then give a copy of this key to Bob. She must make sure that nobody else can get to the key. (So maybe Alice will visit Bob and give him a copy of the key on a memory stick or floppy disc). Now that Bob has a copy of the key, each time Alice needs to send him a message she starts by encrypting it using special encryption software and the secret key. The encrypted message now looks like a jumble of random letters and numbers. Alice then sends the encrypted message to Bob. She can use a public network like the Internet, since, even if it gets stolen, the encrypted message cannot be read or understood without the key.

When Bob receives the message, he uses special decryption software and his copy of the secret key to decrypt the message. Bob can now read the original message from Alice. Advantages a) Data is scrambled into unreadable form/only person/computer with key can understand data b) increasing the length of a key increases the strength of the encryption Disadvantages: a) It is slower than normal browsing. It takes a while for the browser to do the maths required to scramble the message and another delay on the server that has to unscramble the data. b) The recipient may lose the private key. c) It can be a complicated business running a secure server, so very often, ordinary online shops will hire a specialist 'Payment Gateway' such as 'WorldPay' or 'Paypal' to handle payments for them.

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Symmetric Encryption Symmetric encryption is the oldest and best-known technique. A secret key, which can be a number, a word, or just a string of random letters, is applied to the text of a message to change the content in a particular way. This might be as simple as shifting each letter by a number of places in the alphabet. As long as both sender and recipient know the secret key, they can encrypt and decrypt all messages that use this key.

Asymmetric encryption also known as Public-key cryptography Public-key cryptography, also known as asymmetric cryptography, is a class of cryptographic algorithms which require two separate keys, one of which is secret (or private) and one of which is public. Asymmetric Encryption The problem with secret keys is exchanging them over the Internet or a large network while preventing them from falling into the wrong hands. Anyone who knows the secret key can decrypt the message. One answer is asymmetric encryption, in which there are two related keys--a key pair. A public key is made freely available to anyone who might want to send you a message. A second, private key is kept secret, so that only you know it. Any message (text, binary files, or documents) that are encrypted by using the public key can only be decrypted by applying the same algorithm, but by using the matching private key. Any message that is encrypted by using the private key can only be decrypted by using the matching public key. This means that you do not have to worry about passing public keys over the Internet (the keys are supposed to be public). A problem with asymmetric encryption, however, is that it is slower than symmetric encryption. It requires far more processing power to both encrypt and decrypt the content of the message.

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Explain how e encryption ncryption can be used tto o protect data data:: 

On a hard disk

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In e-mail

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On HTTPS websites

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Exam Ques Questions tions Practice

• discuss encryption protocols (including: the purpose of Secure Socket Layer (SSL)/Transport Layer Security (TLS) and the use of SSL/TLS in client server communication)

Secure Socket Layer (SSL) and Certificates SSL stands for Secure Sockets Layer. It provides a secure connection between internet browsers and websites, allowing you to transmit private data online. Sites secured with SSL display a padlock in the browsers URL . What is SSL used for? The SSL protocol is used by millions of e-Business providers to protect their customers, ensuring their online transactions remain confidential. A web page should use encryption expected to submit confidential data, including credit card details, passwords or any personal information. All web browsers have the ability to interact with secured sites so long as the site's certificate is from a recognized certificate authority. SSL exists for two reasons: 

Encryption Hiding what is sent from one computer to another. The data is scrambled up so that it becomes meaningless to someone without the key to decrypt it.

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Identification

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Making sure that t...