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Learn how to use logical operators in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 4c - Logical Operators AND Operator The AND operator is used to execute certain code if more than one thing is true . AND is commonly used with account logins - both the username AND the password must be correct . The example below requires both a secret word and a secret number to be correct: print ( "To enter you need the secret word and the secret number!" ) word = input ( "What is the secret word? " ) number = int ( input ( "What is the secret number? " )) if word == "solitude" and number == 2011: print ( "Correct! You may enter!" ) else : print ( "Incorrect! Get out of here!" ) If no part or only some of the if statement is true then the indented code will not run : To enter you need the secret word and the secret number! What is the secret word? solitude What is the secret number? 4503 Incorrect! Get out of here! To enter you need the secret word and the secret number! What is the secret word? windhelm What is the secret number? 1021 Incorrect! Get out of here! Only If all parts of the if statement are true will the indented code be executed : To enter you need the secret word and the secret number! What is the secret word? solitude What is the secret number? 2011 Correct! You may enter! Logical Operators Task 1 ( Three Easy Questions) Ask the user three easy questions and print a special response if they get all three correct . Use the and operator to see if their answer for all each of the questions is correct. You must use a unique variable nam e for each of your inputs (it can't be 'answer' for all three, for example). Example solutions: What is the capital of Germany? Berlin What is the chemical formula for water? H20 What year did World War Two end? 1945 You absolute genius! What is the capital of Germany? Vienna What is the chemical formula for water? W20 What year did World War Two end? 1945 Bit awkward, I thought you'd do better... OR Operator The OR operator is used to execute certain code if one of several statements is true . The program below is checking if either a , e , i , o or u were entered. letter = input ( "Enter a letter: " ) if letter == "a" or letter == "e" or letter == "i" or letter == "o" or letter == "u" : print ( "You entered a vowel." ) else : print ( "You entered a consonant." ) Enter a letter: f You entered a consonant. Enter a letter: e You entered a vowel. It is important that you re-write the variable and operator (e.g. letter ==) each time you use 'or' . It will not work if you just write: if letter == “a” or “e” or “i” or “o” or “u”: Logical Operators Task 2 ( Twins?) Ask the user to enter their favourite colour and then ask them their age . If their favourite colour is the same as yours AND their age is the same as yours then print “Snap! Are you my twin?” . If only one of the statements is true (use the OR operator) then print “Spooky! You’re a bit like me.” . Add an else statement to print “We’re not so similar, you and I.” if there's nothing in common. Example solutions: What's your favourite colour? green What's your age? 15 Snap! Are you my twin? What's your favourite colour? blue What's your age? 15 Spooky! You're a bit like me. What's your favourite colour? red What's your age? 16 We're not so similar, you and I. ⬅ 4b - Mathematical Opera tors Sectio n 4 Practice Tasks ➡

Learn about malware such as viruses, worms, trojans, spyware, keyloggers and ransomware. Also, learn about phishing, data theft, interception and cyber attacks including SQL injection, IP address spoofing, DDoS attacks and brute force. Based on the 2020 Eduqas (WJEC) GCSE specification. 3.8: Cyber Threats Exam Board: Eduqas / WJEC Specification: 2020 + 3.8a: Malware What is malware? Malware is any type of harmful program that seeks to damage or gain unauthorised access to your computer system. Virus A virus can replicate itself and spread from system to system by attaching itself to infected files . A virus is only activated when opened by a human . Once activated, a virus can change data or corrupt a system so that it stops working . Worm A worm can replicate itself and spread from system to system by finding weaknesses in software . A worm does not need an infected file or human interaction to spread. A worm can spread very quickly across a network once it has infiltrated it. Trojan A trojan is a harmful program that looks like legitimate software so users are tricked into installing it . A trojan secretly gives the attacker backdoor access to the system . Trojans do not self replicate or infect other files. Spyware Spyware secretly records the activities of a user on a computer. The main aim of spyware is to record usernames, passwords and credit card information . All recorded information is secretly passed back to the attacker to use. Keylogger A keylogger secretly records the key presses of a user on a computer. Data is stored or sent back to the attacker. The main aim of a keylogger is to record usernames, passwords and credit card information . Keyloggers can be downloaded or plugged into the USB port . Ransomware Ransomware locks files on a computer system using encryption so that a user can no longer access them. The attacker demands money from the victim to decrypt (unlock) the data . ? ? ? ? Attackers usually use digital currencies like bitcoin which makes it hard to trace them. 3.8b: Data Theft Phishing Phishing is the method of misleading individuals or organisations into sharing sensitive information (such as passwords or bank details ), often through the use of emails . Phishers may pose as a trusted company like Amazon or YouTube to direct users to open malicious attachments or encourage them to follow fraudulent links to steal their data . Social Engineering Social engineering means to trick others into revealing their personal data by posing as a trusted source . For example, impersonating an IT technician of a school via email and asking for a student's username and password . Interception This is when data packets on a network are intercepted by a third party (e.g. a hacker) and copied to a different location than the intended destination. Software called packet sniffers are used to intercept and analyse data packets. Physical Theft Computer systems (e.g. laptops) or storage devices (e.g. USB stick) may be stolen in public or from offices. Unwanted systems and storage media should be disposed of securely as data could be stolen from discarded information , such as old CDs or even printed paper. 3.8c: Online Threats & Attacks Hacking Hacking is the method of exploiting weaknesses in a system or network to create, view, modify or delete files without permission. A hacker is anyone who gains access to data or systems that they do not have authority to access. DoS Attack A DoS (Denial of Service ) attack is when a computer repeatedly sends requests to a server to overload the system . A server overload will slow the system and may take websites offline temporarily. A DDoS (Distributed Denial of Service ) attack is a coordinated attack using a botnet of infected systems to overload a server with requests . A botnet is a large group of devices controlled and used maliciously by an attacker. SQL Injection SQL ( Structured Query Language ) is a programming language used for manipulating data in databases . A SQL injection is when a malicious SQL query (command) is entered into a data input box on a website. If the website is insecure then the SQL query can trick the website into giving unauthorised access to the website’s database . An SQL injection can be used to view and edit the contents of a database or even gain administrator privileges . ' or 1 = 1 Brute Force Attack In order to break a password , every possible combination is tested in order from start to finish . This is not a quick method but it should break the password eventually and can be sped up if multiple computer systems are used at the same time. IP Address Spoofing An attacker changes the IP address of a legitimate host so any visitors to the URL are instead taken to a spoofed ( fake ) web page . This web page is used to record any inputted data (such as usernames and passwords) and send it back to the attacker . The spoofed web page can also be used to install malware . Q uesto's Q uestions 3.8 - Cyber Threats: 3.8a - Malware: 1. What is malware ? [ 2 ] 2a. Describe three characteristics of a virus . [3 ] 2b. Describe three characteristics of a worm . [3 ] 2c. What is a trojan ? [ 3 ] 2d. Describe how spyware and keyloggers work. [ 4 ] 2e. Explain how ransomware works and why it is difficult to trace attackers . [ 3 ] 2f. In your opinion, which malware do you think is the most dangerous and why ? [ 2 ] 3.8b - Data Theft: 1. Describe what is meant by ' phishing ' . [ 2 ] 2. Give an example of social engineering . [ 2 ] 3. What is interception ? What software is used to intercept data packets? [ 2 ] 4. Describe why systems and storage media should be disposed of securely . [ 1 ] 3.8c - Online Threats & Attacks: 1. Describe what is meant by ' hacking ' . [ 2 ] 2a. Describe what a DoS attack is and its impact . [2 ] 2b. Describe how a DDoS attack is different to a DoS attack . [2 ] 3. Describe what an SQL injection is and how an attacker would use it. [ 4 ] 4. Describe what is meant by a brute force attack . [ 2 ] 5. Describe IP address spoofing and its purpose . [ 3 ] 3.7 - The Internet Theory Topics 3.9 - Protection Against Threats

Learn about the differences between wired and wireless networks. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 3.2a: Wired & Wireless Networks Exam Board: OCR Specification: J277 Watch on YouTube : Wired Networks Wireless Networks Encryption Wired Connections Wireless Connections Wireless connections, such as WiFi or Bluetooth , use no cables but require a wireless network interface card (WNIC ). Wireless connections generally have a slower speed and can be affected by the computer's distance from the wireless router as well as obstacles like walls or bad weather. Wired connections use physical cables , such as copper or fibre optic wires , and require a network interface card (NIC ) to connect to a network. These wired connections use a wired connection protocol - most commonly Ethernet . Restricted Movement Faster More Secure NIC Required Freedom of Movement Slower Less Secure WNIC Required Encryption Wireless connections are less secure and require encryption . Encryption is the process of scrambling data into an unreadable format so that attackers cannot understand it if intercepted during transmission. The original data (known as plaintext ) is converted to scrambled ciphertext using an encryption key . Only at the correct destination will the encryption key be used to convert the ciphertext back into plaintext to be understood by the receiving computer. Q uesto's Q uestions 3.2a - Wired & Wireless Networks: 1. Briefly compare wired and wireless networks in terms of movement , transmission speed , security and required hardware . You could answer this in the form of a table. [ 8 ] 3.1b - Network Hardware & Internet Theory Topics 3.2b - Protocols & Layers

The list of topics in the 2020 OCR GCSE Computer Science specifications. OCR GCSE Computer Science (J277) These pages are based on the J277 OCR GCSE Computer Science specification . This website is in no way affiliated with OCR . Component One: Computer Systems OCR GCSE Key Term Generator Paper 1 Playlist on YouTube 1. Systems Architecture 1.1a - The CPU 1.1b - Registers & FE Cycle 1.2 - CPU Performance 1.3 - Embedded Systems 2. Memory & Storage 2.1 - Primary Storage 2.2 - Secondary Storage 2.3 - Units 2.4a - Number Systems 2.4b - Binary Addition & Shifts 2.4c - Character Storage 2.4d - Image Storage 2.4e - Sound Storage 2.5 - Compression 3. Networks 3.1a - Network Types & Performance 3.1b - Network Hardware & Internet 3.2a - Wired & Wireless networks 3.2b - Protocols & Layers 4. Network Security 4.1 - Network Threats 4.2 - Preventing Vulnerabilities 5. Systems Software 5.1 - Operating Systems 5.2 - Utility Software 6. Impacts 6.1a - Impacts of Technology 6.1b - Legislation Component Two: Computational Thinking, Algorithms and Programming Paper 2 Playlist on YouTube 1. Algorithms 1.1 - Computational Thinking 1.2 - Designing Algorithms 1.3 - Searching & Sorting Algorithms 2. Programming Fundamentals 2.1 - Programming Fundamentals 2.2 - Data Types 2.3 - Additional Programming Techniques 3. Producing Robust Programs 3.1 - Defensive Design 3.2 - Testing 4. Boolean Logic 4.1 - Boolean Logic 5. Languages & IDEs 5.1 - Languages & Translators 5.2 - Integrated Development Environment

Learn how to make simple calculations in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 3b - Simple Calculations Simple Calculations in Python You can perform calculations on numbers in Python using the four main operators : print ( 89 + 47) print ( 89 - 47) print ( 89 * 47) print ( 89 / 47) = 136 42 4183 1.8936170212765957 For addition , use the plus sign + To subtract numbers, use the dash symbol – (but not an underscore _ ) For multiplication , use an asterisk * which can be made by pressing Shift and 8 on a typical keyboard. To divide numbers, use a forward slash / (but not a backslash \ ) Use a string and the calculation to make the output user friendly . print ( "53 x 7 =" , 53 * 7) = 53 x 7 = 371 Simple Calculations Task 1 ( + - * /) Print four different simple calculations, using a different operator ( + - * / ) for each. Make the output user friendly by also showing the calculation (not just the answer). Copy the divide symbol here using Ctrl and C : ÷ Example solution: 18 + 35 = 53 18 - 35 = -17 18 x 35 = 630 18 ÷ 35 = 0.5142857142857142 Using Variables in Calculations You can also perform calculations on variables . The example below has the values of the variables pre-written. You need to store the result in a variable . The total variable has been used to store the result of the multiplication. num1 = 12 num2 = 20 total = num1 * num2 print ( "The total is" , total) = The total is 240 The example below allows the user to input values . num1 = int ( input ( "Enter number one: " )) num2 = int ( input ( "Enter number two: " )) total = num1 + num2 print ( "The to ta l is" , total) Enter number one: 21 Enter number two: 82 The total is 103 = Don't leave the user in the dark, better user interfaces are clear and explain what outputted values mean: num1 = int ( input ( "Enter number one: " )) num2 = int ( input ( "Enter number two: " )) answer = nu m1 - num2 print (num1 , "-" , n um2 , "=" , answer) Enter number one: 83 Enter number two: 29 83 - 29 = 54 = Simple Calculations Task 2 ( Divide by 3) Use an input line with int to ask the user to enter a number . Divide the number by 3 and output the result . Example solution: Enter a number: 11 11 divided by 3 is 3.6666666666666665 Simple Calculations Task 3 ( Add 3 Numbers ) Make three input lines using int to ask the user to enter three numbers . Add the numbers together and output the total . Example solution: Enter the first number: 45 Enter the second number: 32 Enter the third number: 19 The total is 96 ⬅ 3a - Data Types Section 3 Practice Tasks ➡

The homepage for all content aimed at Key Stage 3 students studying Computer Science / IT including computer hardware, Python, App Inventor 2 and Cyber Security. Key Stage 3 Topics These topics are aimed at Year 7 - 9 students (11 - 14 year olds) studying computing. Hardware The Motherboard The CPU Memory Expansion Cards Python Basics 1. The Basics 2. Variables 3. Inputs 4. Calculations 5. Selection 6. Turtle 7. Link to GCSE Python Cyber Security Malware Phishing & Staying Safe Other Topics Desktop Publishing

Learn about ethical issues of IT including whistleblowing, discrimination, online safety and bias. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 5.1 - Ethical Issues Exam Board: OCR Specification: 2016 - Unit 1 What are ethics? Ethics refers to what is right and wrong . The following issues are often linked to or backed up by legislation. Whistle Blowing Definition: When a member of staff reveals that the organisation they work for are engaging in unlawful practices . This could include breaking privacy laws , threatening staff or environmental damage . In the UK , whistleblowers are protected by the Public Interest Disclosures Act (1988) . Under this law, whistleblowers are protected from being fired or being victimised (e.g. ignored for promotion ) as a result of their whistleblowing. Large organisations should consider establishing a whistleblowing policy that would outline how employees can raise concerns , who they should speak to and the support available to concerned staff. A famous whistleblower is Edward Snowden , who revealed in 2013 that many governments, including the USA and the UK, were spying on their civilians with widespread undocumented surveillance. Should Martin reveal that his company is dumping old computers into a lake or just stay quiet? Graham feels that, because of his disability, he is being ignored for a promotion that he deserves. Discrimination Definition: When an employee is treated unfairly because of a personal or physical characteristic over which they have no control . The Equality Act (2010) ensures equal treatment for all people irrespective of: race sexuality gender disability marital status (and many more) Examples of discrimination include offensive talk, harassment, unequal pay and being ignored for promotion. Use of Information Definition: Laws such as GDPR (General Data Protection Regulation ) and specifically the Data Protection Act (2018) ensure that organisations must responsibly process personal data. Organisations have a legal obligation to keep their employee and customer personal data secure and out of reach from unauthorised viewers. Considerations should be made about how the information is ethically collected , stored and processed . DataDyne backs up customer information on cloud storage - what if this data is compromised ? As part of quality assurance, Selside Bank double check performance reviews before submission. Codes of Practice Definition: A set of rules which explains how people working in certain professions are required to behave . Organisations may have a code of practice for: Confidentiality (rules on what data can and cannot be shared with others), Quality assurance (ensuring high quality is maintained for all products/services), Behaviour (setting out how employees are expected to behave at work and in communication with each other and customers), Equality and discrimination (being understanding and providing fair access to all employees). Employees must agree to the codes of practice so they are clear on their expectations of what is and isn't acceptable at work. The organisation can then discipline employees that broke the codes of practice they formerly agreed to. Online Safety Definition: Often companies will provide an induction (training ) to new employees about the organisation’s code of practice for using the internet whilst at work . If an individual does not behave safely online or breaks the organisation's codes of practice (by gambling at work for example) then they may be punished (e.g. fined or fired). Employees can ensure that they are safe online by using secure passwords that are regularly updated and preventing web browsers from remembering login details . Miriam changes her password each month to minimise the chance of hackers accessing her account. The CEO of Honey Media apologies in public after biased information led to a lawsuit and loss of reputation. Bias Definition: This is technically correct, but slanted , information that presents a one-sided view . For example, end-of year financial data that focuses on profits and ignores significant losses. Poor quality information may lead to an organisation being misinformed and not sufficiently responding to their customers' needs - for example if a survey was only completed by a small number of people it could generate biased results. As a result of poor quality information, organisations may suffer from damage to their reputation due to negative feedback and reviews from customers, possibly posted online. A lack of trust can occur if customers feel neglected because of decisions made using biased information of a poor quality, therefore reputational damage may lead to loss of customers . Q uesto's Q uestions 5.1 - Ethical Issues: 1. Describe what whistleblowing is and give 3 examples . [4 ] 2. Describe what discrimination is and give 4 examples . [5 ] 3. Which law relates to the use of information ? [1 ] 4a. Describe 2 things that may be included in an organisation's codes of practice . [4 ] 4b. Explain why employees must agree to their company's codes of practice [4 ]. 5. Describe 2 things an employee should do to stay safe online . [2 ] 6a. What is biased information ? [2 ] 6b. Describe 3 possible effects to a company if they use biased information . [6 ] 4.6 & 4.7 - Bodies & Certification Topic List 5.2 - Operational Issues

Learn about the differences between open and closed information systems. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 3.6 - Information Systems Exam Board: OCR Specification: 2016 - Unit 2 Information systems, such as structured databases , can be defined primarily as either 'open ' or 'closed '. Open Information Systems Closed Information Systems This type of system can interact with other information systems (e.g. another database) to exchange data , even from different platforms (types of computers). Because it is open it is more at risk of data loss and/or hacking. This type of system is private and cannot exchange data with other systems. Access is limited but it is much more secure than an open system. Q uesto's Q uestions 3.6 - Information Systems: 1. Compare and contrast open and closed information systems . [4 ] 3.5 - Data Analysis Tools Topic List 4.1 - UK Legislation

Learn about common prevention methods of minimising cyber security risks including anti0malware, firewalls and penetration testing. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 4.2: Preventing Vulnerabilities Exam Board: OCR Specification: J277 Watch on YouTube : Preventing Vulnerabilities Penetration Tests Penetration tests are carried out as part of ethical hacking. The purpose of a penetration test is to review the system's security to find any risks or weaknesses and to fix them . Internal tests are to see how much damage could be done by somebody within the company with a registered account. External tests are for white hat hackers to try and infiltrate a system from outside the company . Anti-Malware Software Anti-malware software is used to locate and delete malware, like viruses, on a computer system. The software scans each file on the computer and compares it against a database of known malware . Files with similar features to malware in the database are identified and deleted . There are thousands of known malware, but new forms are created each day by attackers, so anti-malware software must be regularly updated to keep systems secure. Other roles of anti-malware software: Checking all incoming and outgoing emails and their attachments . Checking files as they are downloaded . Scanning the hard drive for viruses and deleting them . Firewall A firewall manages incoming and outgoing network traffic . Each data packet is processed to check whether it should be given access to the network by examining the source and destination address . Unexpected data packets will be filtered out and not accepted to the network. Other roles of a firewall include: Blocking access to insecure / malicious web sites . Blocking certain programs from accessing the internet . Blocking unexpected / unauthorised downloads . Preventing specific users on a network accessing certain files . Secure Passwords ******** Usernames must be matched with a secure password to minimise the chances of unauthorised users accessing a system. Passwords should contain a mix of uppercase and lowercase letters , punctuation and numbers . Passwords should be of a substantial length (at least 8 characters) and should be regularly changed . User Access Levels Access levels are used to only allow certain users to access and edit particular files. ' Read-Only ' access is when a user can only view a file and is not allowed to change any data . For example, a teacher might set homework instructions as read-only for students to view. ' Read and Write ' access allows a user to read and edit the data in a file. For example, a teacher might set an online workbook as read and write access for students to fill in. It is important to set access levels so that only authorised users can view and change data. The more users who have access to a file, the more likely it is to be compromised. Certain users may also have no access to a file - when they can't view or edit it. Encryption Encryption is the process of scrambling data into an unreadable format so that attackers cannot understand it if intercepted during transmission. The original data (known as plaintext ) is converted to scrambled ciphertext using an encryption key . Only at the correct destination will the encryption key be used to convert the ciphertext back into plaintext to be understood by the receiving computer. Physical Security A lock can be used to prevent access to server rooms or locations that store confidential data . Only authorised personnel with a matching key will have access. Biometric devices require the input of a human characteristic (such a fingerprint , iris or voice ). The biometric data is checked against previously inputted data in a database. Only a match will allow access to the user. Other forms of physical security include keycards , security staff , CCTV cameras and alarms . Q uesto's Q uestions 4.2 - Preventing Vulnerabilities: 1. Describe the purpose of penetration tests . [2 ] 2. Describe the purpose of anti-malware software and its different roles . [ 4 ] 3. Describe the purpose of a firewall and its different roles . [ 4 ] 4. State three rules for choosing a strong password . [ 3 ] 5. Describe the three types of access level . [6 ] 6a. Describe the purpose of encryption . [ 2 ] 6b. Explain how encryption works, using the terms plaintext , key and ciphertext . [ 4 ] 4.1 - Security Threats Theory Topics 5.1 - Operating Systems

Learn about the methods of digital protection including antimalware, firewalls and obfuscation. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 6.6 - Logical Protection Exam Board: OCR Specification: 2016 - Unit 2 Logical protection refers to using digital methods of security to protect computer systems and data. Usernames & Passwords ****** Anti-Malware Usernames must be matched with a secure password to minimise the chances of unauthorised users accessing a system. Passwords should contain a mix of uppercase and lowercase letters , punctuation and numbers . Passwords should be of a substantial length (at least 8 characters) and should be regularly changed . Anti-virus software scans a system and removes viruses . If left to infect a system a virus could delete data or permit access to unauthorised users . Anti-spyware software removes spyware on an infected system so hackers cannot view personal data or monitor users. Organisations should install and regularly update anti-virus and anti-spyware programs. Firewall Encryption Firewalls prevent unauthorised access to or from a network . Firewalls filter data packets and block anything that is identified as harmful to the computer system or network. Firewalls can also be used to block access to specific websites and programs. A firewall can be in the form of a physical device which is connected to the network, or software installed on a computer system. Encryption is the conversion of data ( plaintext ) into an unreadable format ( ciphertext ) so it cannot be understood if intercepted . Encrypted data can only be understood by an authorised system with a decryption key . There are two types of encryption . Encryption at rest is when data is encrypted while it is being stored on a system or storage drive. Encryption in transit is to secure the data as it being transferred between systems on a network. Tiered Levels of Access Obfuscation ?????? The purpose of tiered levels of access is to grant different types of permission to certain users. Managing levels of file access ensures that only authorised people can access and change certain files . There are different levels of file access : No access Read-only - Allows a user to view but not edit. Read/write - Allows a user to view and edit. Obfuscation is when data is deliberately changed to be unreadable to humans but still understandable by computers . Program code might be obfuscated to stop rival programmers from viewing and stealing it if they were able to access it. Specialist software can be used to obfuscate data and convert it back into a human-readable format. Q uesto's Q uestions 6.6 - Logical Protection: 1a. Describe why usernames and strong passwords are necessary. [2 ] 1b. State 3 rules for choosing a strong password . [3 ] 2. Describe the purpose of anti-virus and anti-spyware software. [4 ] 3. Describe the roles of a firewall . [4 ] 4. Explain what encryption is. What are the two types? [4 ] 5. Why would an organisation use tiered levels of access ? What are the 3 levels of file access ? [5 ] 6. What is obfuscation ? State a scenario in which it would be used. [3 ] 6.5 - Physical Protection Topic List

Learn about different data structures such as arrays, lists and records. Also, the difference between static and dynamic data structures and how to design files. Based on the 2020 Eduqas (WJEC) GCSE specification. 5.1: Data Structures & File Design Exam Board: Eduqas / WJEC Specification: 2020 + What is a Data Structure? A data structure is a way of efficiently organising data . There are two general forms of data structures: Static Data Structures The size of a static data structure cannot change e.g. if a data structure has 20 elements, no additional elements can be added or removed. The values of the data elements can be changed, but memory size is fixed when allocated at compile time. Because a static data structure holds a certain number of data elements they are easier to program because the size of the structure and the number of elements never change. An array is an example of a static data structure. Examples: A static data structure could be an array of teams in the Premier League. The data elements will change each year when teams are relegated and promoted but there will always be 20 teams. Dynamic Data Structures The size of a dynamic data structure can change as the program is being run , it is possible to add or remove data elements. Dynamic data structures make the most efficient use of memory but are more difficult to program , as you have to check the size of the data structure and the location of the data items each time you use the data. A list is an example of a dynamic data structure. A dynamic data structure could be a list of all teams in the Premier League that won their last match. Data elements (teams) will be added or removed across the season. Types of Data Structures List A list is a dynamic data structure that has the data elements stored in the order they were originally added to memory . Every data structure starts at 0, not 1 . Lists store data elements in the order they were added, so the first doctor is 0 and the most recent doctor is 12. An example list of the main Doctor Who actors Array An array is a static data structure that can hold a fixed number of data elements . Each data element must be of the same data type i.e. real, integer, string. The elements in an array are identified by a number that indicates their position in the array. This number is known as the index. The first element in an array always has an index of 0 . You should know how to write pseudo code that manipulates arrays to traverse, add, remove and search data. The following steps uses Python as an example. Traversing an Array To traverse (' move through ') an array a for loop can be used to display each data element in order. 'Inserting' a value In an array the size is fixed so you cannot insert new values, but you can change the value of elements that already exist. Overwriting the fourth element (Daphne) with a new value (Laura) will change it from Daphne to Laura. Example code for traversing: Example code for inserting: Output: Output: 'Deleting' a value In an array the size is fixed so you cannot delete values, but you can overwrite them as blank . Overwriting the second element (Shaggy) with a blank space makes it appear deleted. Example code for deleting: Output: Searching an Array For large arrays a for loop is needed to search through each element for a specific value . This example checks each name to see if it is equal to Velma. Example code for searching: Output: Two-Dimensional Array Often the data we want to process comes in the form of a table . The data in a two dimensional array must still all be of the same data type , but can have multiple rows and columns . The two-dimensional array to the right shows the characters from Scooby Doo along with their associated colour and their species. Each value in the array is represented by an index still, but now the index has two values . For example [3] [0] is 'Daphne'. We measure row first , then column . Searching a two-dimensional array: To print a specific data element you can just use the index number like Daphne above. To search for a specific value you will need two for loops, one for the row and another for the values of each row. The example to the right is looking for the value of 'Velma' and when it is round it prints the associated data from the whole row. Example code for printing: Output: Example code for searching: Output: Records Unlike arrays, records can store data of different data types . Each record is made up of information about one person or thing. Each piece of information in the record is called a field (each row name). Records should have a key field - this is unique data that identifies each record . For example Student ID is a good key field for a record on students as no two students can have the same Student ID. Data files are made up of records with the same structure. It would be most efficient for the fields in a record to be stored next to each other so that the data can be read into the record data structure in memory for processing by the CPU. In an exam you may be asked to state and design a data structure for a given scenario. If the data structure can hold values of the same data type you should draw an array , usually a 2D array for multiple rows and columns. Remember that a record is required to store values of different data types . Example questions: "A video gamer has recorded their three lap times in four Mario Kart courses." " State and design the most suitable data structure for this data." A two-dimensional array is most suitable because only one data type ( real ) is stored. "A vet surgery stores data on all dogs and cats including the animal's name, age (in years), weight (in kg) and whether or not it has been vaccinated." " State and design the most suitable data structure for this data for four animals ." A record is most suitable because the data structure requires different data types . Q uesto's Q uestions 5.1 - Data Structures: 1. Give two differences between static and dynamic data structures . [ 4 ] 2. Describe the differences between a list , array and record . [ 3 ] 3. A one-dimensional array looks like this: TigerBreeds("Sumatran","Indian","Malayan,"Amur") Write the code to: a. Print the element with the index of 3. [ 2 ] b. Change Indian to South China. [ 2 ] c. Remove the Amur element. [ 2 ] d. Search through the array for 'Malayan'. [ 2 ] 4. State and design the most suitable data structure for these scenarios: a. For each book in a bookshop, the staff need to record the title, author, number of pages and whether or not it is a signed copy. Include data for three books. [ 3 ] b. Four dieters are recording how many kilograms they have lost each month for 5 months. [ 4 ] 5. Design a file that stores the first initial, surname, age and hair colour of each member of a family. [ 8 ] Designing Data Structures Data is stored in files when it needs to be kept after the program has stopped running . To learn how to write code for file handling (e.g. opening, writing to, reading from and closing files) in Python click here . Designing a file requires more than just the field name (e.g. Name) and data values (e.g. Rebecca). The data type (e.g. string) and any validation checks (e.g. format check) should also be considered. Below is an example file design for a bakery. Designing Files 4.8 Compression Theory Topics 6.1 - Operating Systems

Learn about methods of physically protecting data such as biometric devices, RFID and tokens, privacy screens and shredding. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 5.4 - Physical Security Exam Board: OCR Specification: 2016 - Unit 1 RFID & Tokens Radio-frequency identification (RFID) uses electromagnetic fields to attach tags to physical objects . RFID tags can be embedded within 'dumb' objects such as clothing, packages and even animals. RFID is used with security tokens (such as an ID keycard ) to permit the access of authorised people to certain areas. RFID can be used by IT companies to track equipment and manage access . Shredding This is the cutting up of documents (paper or CDs ) into small pieces so that they cannot be reassembled and read. Sensitive data on paper or optical disc should be shredded when no longer required. Locks A lock can be used to prevent access to server rooms or sensitive data stores . Only authorised personnel with the right key will have access. Physical Security Measures Biometrics Biometric devices require the input of a human characteristic (such a fingerprint , iris or voice scan ). The biometric data is checked against previously inputted data in a database . A match will allow access to the user. See more in section 1.1 . Privacy Screens These plastic screens are placed over a monitor to obscure the screen to anyone except the person sitting directly in front of them. This prevents shoulder surfing and prevents data from being read by unauthorised people nearby. Q uesto's Q uestions 5.4 - Physical Security: 1. Explain how locks can be used as a physical security method within an organisation. [2 ] 2. Explain what RFID is and how it can be used with tokens as a physical security method. [3 ] 3. Explain how biometric devices can be used as a physical security method. [3 ] 4. Explain how privacy screens are used to protect data. [2 ] 5. What is the purpose of shredding ? [2 ] 5.3 - Threats Topic List 5.5 - Digital Security