Learn about network forensics, penetration tests and methods of protection including anti-malware, firewalls, encryption and two-factor authentication. Based on the 2020 Eduqas (WJEC) GCSE specification. 3.9: Protection Against Threats Exam Board: Eduqas Specification: 2020 Network Forensics & Penetration Testing What is network forensics? Network forensics is the monitoring of a network to identify unauthorised intrusions . Network forensics is used to record and analyse attacks on a network and to gather other information about how the network is performing. It is important for organisations to identify weaknesses in their networks so that they can fix them and be prepared for any type of attack or malware. Footprinting - Footprinting is one method of evaluating a network’s security . This is when a security team puts itself in the attacker’s shoes by obtaining all publicly available information about the organisation and its network . Footprinting allows the company to discover how much detail a potential attacker could find out about a system. The company can then limit the technical information about its systems that is publicly available . Penetration Tests Penetration tests are carried out as part of ethical hacking. Ethical hacking is when an organisation gives permission to specific 'good ' hackers to try and attack a system so that the weak points can be highlighted and then fixed. The purpose of a penetration test is to review the system's security to find any risks or weaknesses and to fix them . There are four main types of penetration tests : 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 . Blind tests are done with no inside information , to simulate what a real attacker would have to do to infiltrate the system. + Targeted tests are conducted by the company's IT department and the penetration team cooperating together to find faults in the system. Anti-Malware & Firewalls 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 . Other Methods of Protection Double Authentication Also known as two-factor authentication (2FA ), this is a method of confirming someone's identity by requiring two forms of authorisation , such as a password and a pin code sent to a mobile. 4392 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. A very simple method of encryption is to use the XOR logical operator . XOR is used on the plaintext and key together to create the ciphertext . Using XOR again on the ciphertext and key will reverse the encryption to reveal the plaintext . Encryption using XOR Plaintext = 00110100 Key = 10100110 XOR Ciphertext = 10010010 Decryption using XOR Ciphertext = 10010010 / Key = 10100110 XOR Plaintext = 00110100 Q uesto's Q uestions 3.9 - Protection Against Threats: 1a. What is network forensics ? Why is it important ? [ 3 ] 1b. Explain what is meant by footprinting and why companies do it . [ 2 ] 2. What is an ethical hacker ? [2 ] 3a. Describe the purpose of penetration tests . [2 ] 3b. Describe each type of penetration test . [ 8 ] 4. Describe the purpose of anti-malware software and its different roles . [ 4 ] 5. Describe the purpose of a firewall and its different roles . [ 4 ] 6a. Describe double authentication . [2 ] 6b. State three rules for choosing a strong password . [ 3 ] 7. Describe the three types of access level . [6 ] 8a. Describe the purpose of encryption . [ 2 ] 8b. Explain how encryption works, using the terms plaintext , key and ciphertext . [ 4 ] 3.8 - Cyber Threats Theory Topics 4.1 - Number Systems

Learn about network operating systems, open source operating systems and proprietary operating systems. Resources based on Unit F160 (Fundamentals of Application Development) for the OCR Cambridge Advanced Nationals in Computing (H029 / H129) AAQ (Alternative Academic Qualification). Qualification: Cambridge Advanced National in Computing (AAQ) Unit: F160: Fundamentals of Application Development Certificate: Computing: Application Development (H029 / H129) 1.2 - Operating Systems Watch on YouTube : Network Operating System Open Operating System Proprietary Operating System An operating system is software that manages the resources of a computer system , such as memory , users and files . It also provides a user interface so that humans can interact with the device's hardware . An operating system allows application software to be opened and run . There are three types of operating system that you need to know - network , open and proprietary . Operating Systems Network Operating System (NOS) A network operating system (NOS ) is software that manages network resources and allows computers to communicate over a network . Windows Server , developed by Microsoft , is an example of a network operating system . Characteristics of a Network Operating System Allows for the centralised management of users , data and security across multiple devices on a network . Enables resources such as files , applications and printers to be shared over the network . Manages user authentication and permissions control . Oversees remote access and system monitoring tools . The main type of device that uses a NOS is a server . Other devices, such as desktops or laptops , connect to the server to access shared resources . Windows Server is an example of a popular NOS . Advantages of a Network Operating System Administrators can manage users , files and security on a network from one central location . Resources such as files , printer access and applications can be shared across the network . Access levels can be controlled and user authentication helps protect data . An NOS is scalable - more devices and users can be added as needed . Central servers managed by a NOS make it easier to back up and restore important files . Disadvantages of a Network Operating System Purchasing a NOS and maintaining the servers it runs on can be expensive . Setup and management is complex and may require skilled administrators . If the main server running the NOS fails , connected computers may lose access to resources . Heavy traffic or poor configuration could slow the network down . Who uses a Network Operating System? Application developers can use a NOS to build , test and manage apps that work across networks , such as web applications , multiplayer games or cloud tools . This type of operating system is also used by organisations that need to manage multiple devices , users and resources efficiently across a network , such as a small business or a school . Open Operating System An open operating system is open-source , meaning its source code is freely available for anyone to view , modify and distribute . Source code is the original set of instructions written by a programmer using a high-level language such as Python , Java or C++ . Characteristics of an Open Operating System Users have access to the source code and can see how the OS works . The source code can be modified to suit the specific needs of the user . Development and maintenance may be led by an online community . An open OS is usually free with no licensing costs for most versions. Linux is an example of an open operating system . Android is technically an open-source OS , but most commercial Android devices (like Google Pixel phones ) include proprietary components (like Google Docs or Gmail ), which makes the full system not completely open source . Advantages of an Open Operating System It is usually free to use , modify and distribute the source code . Because the source code can be seen and modified , this type of OS is flexible and customisable . There may be updates from an online community maintaining and improving the software . Promotes experimentation to learn how systems work and try new ideas . Disadvantages of an Open Operating System Programming knowledge and skills are required to modify the source code . There may be security risks if someone edits the source code and redistributes it with malicious code . There will be less official support compared to a proprietary operating system . Some proprietary applications (like Microsoft Access for databases) will only work on a proprietary OS (like Windows ). Who uses an Open Operating System? App developers would use an open OS when the device their application will be used on is not tied to a specific proprietary system (like Windows or MacOS ). For example, a charity making a free educational app for developing countries would choose an open OS so it can run on low-cost , older smartphones . It can be customised and tested on a range of devices . Applications for specific single-purpose systems would also use an open OS , such as an information terminal in a museum . Linux could be used to develop a simple user interface and remove unnecessary features . Proprietary Operating System A proprietary operating system is software that is owned by a company or individual and the source code is not accessible for users to view , modify or distribute . Users must typically buy a licence or agree to the terms of use . Characteristics of a Proprietary Operating System The source code is hidden from the user and cannot be legally modified . A paid licence or subscription is usually required to use the software . It may be maintained and updated by the developer(s) who own it . Only the developer controls updates and the features that are added or fixed . Examples include Microsoft Windows (e.g. Windows 11 ), macOS (for Apple desktops and MacBooks ), iOS (for iPhones ) and iPadOS for iPads ). Advantages of a Proprietary Operating System There is an expectation that it is user-friendly and has been well tested . There may be official support and regular updates for improvements and bug removal . A proprietary OS has a high compatibility with proprietary software such as Microsoft Office or Adobe editing apps . The OS is expected to be stable and secure , with access restricted to system files . Disadvantages of a Proprietary Operating System A paid licence to use the OS is often required , which may be expensive . There is limited customisation for users as the source code cannot be seen or modified . Users rely on the vendor (developer ) for updates and bug fixes . Some proprietary OS are designed to only work on specific hardware (such as iOS only working on iPhones ). Who uses a Proprietary Operating System? App developers will need to use a proprietary OS if they are developing applications for a device that requires a specific proprietary OS , for example if they are creating a game for iPhones , they will need to use iOS . A company designing a finance application on desktops with Microsoft Access and Microsoft Excel must use a proprietary OS like Windows so that it can be integrated with these other types of proprietary applications . Q uesto's Q uestions 1.2 - Operating Systems: 1. What is an operating system ? [2 ] 2. For each of the three types of operating systems , create a poster , information sheet or factfile which includes the following information : Characteristics Advantages Disadvantages Example of how it could be used [10 per OS ] Windows 11 is Microsoft's current operating system . Windows 1.0 was their first release, introduced in 1985 and included basic versions of Calculator , Notepad and Paint . D id Y ou K now? 1.1 - Programs & Applications Topic List 1.3.1 - Application Types

Test your understanding of data structures such as lists (one-dimensional and two-dimensional) and dictionaries. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python - Section 8 Practice Tasks Task One Write a program with a blank list. Use the .append() command to add your three favourite ice-cream flavours to this list and then print the list. Example solution: Task Two Write a program with a list of any 5 numbers. Print the list. Delete the first and third numbers. Print the list. Example solution: Task Three Write a program with a list of three different animals. Write an input line that lets the user type an animal. Add what the user has written to the list and print the list. Example solution: Task Four Sort your list from task two into order. Then print the list. Example solution: Task Five Copy the text on the right and put it into a list named countries. Count the number of countries in the list. Print the longest country. Use a for loop to work out the length of each country. "Egypt", "Angola", " Eritrea " , "Mozambique" , "Ghana" , "Chad" , "Somalia" , "Namibia" , "Sudan" , "Libya" , "Algeria", "Morocco" , "Cameroon" Example solution: Task Six Create a dictionary (see 8c ) that asks users questions about yourself, such as first name, favourite colour or birthday. Let the user answer each question and display the answer if they get it correct. Use the 'Using a Dictionary to Make a Game ' section of 8c to help you. Example solution: ⬅ 8c - Dictionar ies 9a - String Handling ➡

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

Learn about the factors that affect the performance of networks, as well as different types of network types such as LAN and WAN. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 3.1a: Network Types & Performance Exam Board: OCR Specification: J277 Watch on YouTube : LAN & WAN Network Performance Client-Server Network Peer-to-Peer Network Star Topology Mesh Topology What is a network? A network is more than one computer system connected together allowing for communication and sharing of resources . Network Types Networks can be split into different types , usually categorised by their geographical distance apart and the area that they serve. Local Area Network Wide Area Network Client-Server Network Clients make requests to a server , the server manages that request and responds. For example, if the user (client) makes a request to access www.bbc.co.uk to a web server. Large services like Amazon and Google will need very powerful servers to handle millions of requests a second. The client is completely dependent on the server to provide and manage the information. The server controls network security , backups and can be upgraded to manage higher demand. Advantages: The network can be controlled centrally from the server to easily backup data and update software . Hardware, software and resources can be shared across the network, such as printers, applications and data files . The network allows for improved scalability , meaning more clients can be easily added to the central server . Disadvantages: Large amounts of traffic congestion will cause the network to slow down . If a fault occurs with the server then the whole network will fail . IT technicians may be required to manage and maintain the network . Malware , such as viruses, can spread quickly across the network. Peer-to-Peer Network For peer-to-peer networks , data is shared directly between systems without requiring a central server . Each computer is equally responsible for providing data. Peer to peer is optimal for sharing files that can then be downloaded. Disadvantages: Without a dedicated server there is no central device to manage security or backups . Backups must be performed on each individual system. Computer performance will decrease with more devices connected to the network, especially if other machines are slow. Advantages: This is a simpler network than client-server to set up as no server is required . Clients are not dependent on a server . Perfect for quickly sharing files between systems , such as downloading media files. A local area network (LAN ) has computer systems situated geographically close together , usually within the same building or small site , like a school or office . The network infrastructure of a LAN (such as servers and routers) is usually owned and managed by the network owner . A wide area network (WAN ) has computer systems situated geographically distant to each other, possibly across a country or even across the world . WANs often use third party communication channels , such as connections by internet services providers like BT or Virgin Media. Data Packets When sending data across a network, files are broken down into smaller parts called data packets . Whole files are too large to transfer as one unit so data packets allow data to be transferred across a network quickly . Each packet of data is redirected by routers across networks until it arrives at its destination. Data packets may split up and use alternative routes to reach the destination address. When all the packets have arrived at the destination address the data is reassembled back into the original file. What is a network topology? Network topology refers to layout of computer systems on a local network . Devices in a network topology diagram are often called 'nodes' . Two types of typology are star and mesh . Star Topology Each computer system is connected to a central device , usually a hub or switch . How it works: Each computer system is connected to the central hub or switch and transfers its data packets there. The hub or switch looks at the destination address and transfers the packets directly to the intended computer. Advantages: A star topology has improved security because data packets are sent directly to and from the hub / switch in the centre and not necessarily all devices like in a bus or ring topology. New systems can be attached directly to the central system so the network doesn't need to be shut down . System failures of attached computers won't usually cause complete network failure. Transfer speeds are generally fast in a star topology as there are minimal network collisions . Disadvantages: Extra hardware (the hub or switch) is required to be purchased, installed and maintained. If the central system (the hub or switch) fails then the whole network will be unusable until the error is fixed. Mesh Topology In a full mesh network, each computer system is connected to every other computer system . There is also a partial mesh network where only some nodes (e.g. a printer) are connected to every other node. How it works: Data packets are transferred to the destination address along the quickest path , travelling from node to node. If a pathway is broken , there are many alternative paths that the packets can take. Advantages: If one cable or system fails then data packets can take an alternative route and still reach the destination address. Because of the large possible number of systems and connections, a mesh topology can usually withstand large amounts of data traffic . New systems can be added to the network without disrupting the entire topology . Disadvantages: Because of the possibly large amount of cables required (especially in a full mesh topology) this network layout can be expensive to install and maintain . Redundant cabling should be avoided - this is when cables are connected between systems that won't ever need to communicate . Performance There are several different factors that can affect the performance ( speed ) of a network, such as: The bandwidth available * Interference (e.g. thick walls) Number of users at the same time Distance to travel / signal strength Number of data collisions Amount of data to transfer * Bandwidth is the maximum amount of data that can be sent across a network at once . Q uesto's Q uestions 3.1a - Network Types & Performance: 1a. Describe the difference between a LAN and WAN . [2 ] 1b. Give an example of how a LAN and a WAN could each be used . [ 2 ] 2 a. Describe how peer-to-peer networks and client-server networks function. 2b. Give one use for both types of network. 3. Draw and label diagrams of client-server , peer-to-peer , star and mesh networks. [8 ] 4. An office currently uses a star topology but is considering changing to a mesh topology . Describe two advantages and two disadvantages of both topologies. [ 8 ] 5. State five factors that could affect the performance of a network . [5 ] 2.5 - Compression 3.1b - Network Hardware & Internet Theory Topics

Learn about the laws related to computing - the Data Protection Act, Computer Misuse Act, Copyright Design and Patents Act and Regulation of Investigatory Powers Act. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level Specification: Computer Science H446 5.1 - Computing-related Legislation Watch on YouTube : Data Protection Act Computer Misuse Act Copyright, Designs and Patents Act Regulation of Investigatory Powers Act Several key UK laws govern the ethical and legal use of computers and digital information including the Data Protection Act and Computer Misuse Act . Each act is designed to protect data , users or intellectual property in the digital age. Data Protection Act (2018) The Data Protection Act is a UK law designed to ensure that personal data is collected , stored and used responsibly . It gives individuals (data subjects ) rights over their personal information and sets rules for organisations that process it . Introduced in 1998 , it was updated in 2018 to align with the EU’s General Data Protection Regulation (GDPR ). The Data Protection Act's key principles include that data must be processed lawfully , fairly and transparently , used for specific purposes , kept accurate and up to date , stored securely and not kept longer than necessary . It also gives data subjects rights such as accessing their data , correcting inaccuracies , objecting to processing and requesting deletion . Organisations that break the law can face heavy fines and legal action from the Information Commissioner’s Office (ICO ). Computer Misuse Act (1990) The Computer Misuse Act (1990 ) is a UK law created to make unauthorised access and use of computer systems illegal . It was introduced in response to the rise of hacking and other cybercrimes as computers became more common . This act defines several offences , including: Unauthorised access to computer material , such as hacking into a system without permission . Unauthorised access with the intent to commit further offences , such as fraud or data theft . Unauthorised modification of data or programs , for example, spreading viruses or deleting files . Making , supplying or obtaining tools used for committing these offences . Penalties range from fines to imprisonment , depending on the severity of the crime . This act helps protect individuals , organisations and data from malicious attacks and misuse . Copyright, Designs & Patents Act (1988) The Copyright, Designs and Patents Act (1988 ) is a UK law that protects people’s creative and intellectual work from being copied or used without permission . It gives creators automatic legal rights over their original work , such as books , music , films and software . The act states that the copyright owner controls how their work is used , including the rights to copy , distribute or adapt it. Anyone wishing to use the work must get permission or a licence from the owner. It also includes exceptions , allowing limited use for purposes like education or research . This act helps ensure that creators are fairly rewarded for their work and that their intellectual property is legally protected . Regulation of Investigatory Powers Act (2000) The Regulation of Investigatory Powers Act (RIPA ) (2000 ) is a UK law that governs how public bodies and law enforcement can carry out surveillance and access electronic communications . It was introduced to balance national security and crime prevention with individuals’ right to privacy . RIPA allows authorised agencies , such as the police , intelligence services and local councils , to monitor communications , intercept phone calls or emails and use covert surveillance , but only with proper legal authorisation . It also regulates the use of informants and access to encrypted data . This act aims to ensure that surveillance is done lawfully , proportionately and for legitimate purposes , such as preventing or detecting serious crime or protecting public safety . Q uesto's K ey T erms Legislation: Data Protection Act (2018) Computer Misuse Act (1990) Copyright Design and Patents Act (1988) Regulation of Investigatory Powers Act (2000) D id Y ou K now? In 1985 , two journalists were arrested for ‘ hacking ’ into the emails of the Duke of Edinburgh ( Prince Philip ) after discovering an engineer’s username was ‘ 2222222222 ’ and password was ‘ 1234 ’. They were acquitted in court because no UK laws covered hacking , exposing a major legal gap that led to the creation of the Computer Misuse Act ( 1990 ) . 4.3 - Boolean Algebra A-Level Topics 5.2 - Moral & Ethical Issues

Learn how to easily remove objects in Greenfoot in only two lines of code. Part 4 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. 4. Remove Objects Greenfoot Tutorial 1. Removing Objects Watch on YouTube: Open the editor for your main character . Underneath the if statements for using the arrow keys is where we type the removal code . If you have chosen a different collectible object, type the exact name of that class instead of Orange (e.g. Apples or Ants). 2. Add Danger to your Game Use the same code as you did earlier but change the class (instead of Orange. class I have chosen Sheep. class ). Time to code your main character to be removed if they are touched by the enemy objects ! Open the editor for your enemy class . The removal code is placed beneath the code you have already written. Check out the extension page if you want the game to stop when the main character is removed. < Part 3 - Random Movement Part 5 - Play Sounds >

Consider multiple extensions to increase the complexity of your Greenfoot game. Part 7 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. 7. Extension Ideas Greenfoot Tutorial This concludes the tutorial for a simple Greenfoot game! Try a combination of the suggestions below to add complexity to your game: 1. Make a New Class for 'Bad' Collectibles Create a new subclass in the Actor classes section for a new collectible that will lower the score if picked up. Add code to your main character to remove the collectible when they touch . Add code to decrease the counter by 1 at the same time. 2. Make the Collectibles Move Randomly Copy the code from your enemy class that makes it move randomly and bounce on edge , and paste this into your collectible class . This makes it harder to catch the collectables, especially if there are 'bad' objects to avoid. 3. Stop the Game Go to the code of your enemy and add the line underlined in red within your removal code. This will stop the game if your main character is eaten. 4. Make the Game Multiplayer Create a new subclass in the Actor classes section for a new main character that will be controlled by a second player . Add code to your new character to move it right, down, left and up . Choose different keys for each direction , such as the WASD keys or IJKL keys. If the second player touches a collectible , add code to decrease the score . Multiplayer Rules: Player 1 wins if the final score is above 0 . Player 2 wins if the final score is negative . It is a draw if it finishes on 0 . < Part 6 - The Counter

Learn about how to perform binary addition and binary subtraction. Based on the 2020 Eduqas (WJEC) GCSE specification. 4.3: Binary Calculations Exam Board: Eduqas Specification: 2020 What are binary calculations? Binary addition and binary subtraction are methods of adding or subtracting binary values without having to convert them into denary. How to add binary numbers: How to subtract binary numbers: Overflow & Underflow Errors Overflow and underflow errors occur when there is not enough space to accurately represent a binary number in the bits available . What is an overflow error? An overflow error occurs when a binary value is too large to be stored in the bits available . In technical terms, an overflow error occurs if a carry (remainder) is present on the most significant bit (MSB ). The CPU then sets the overflow flag to true . The most significant bit (MSB ) is the largest bit (always the one furthest to the left ) of a binary value (e.g. 128 for an 8 bit value). A flag is an alert signal . It is either on or off. The overflow flag is turned on by the CPU when an overflow occurs. What is an underflow error? An underflow error occurs when a number is too small to be stored in the bits available . The value is too close to 0 to be accurately represented in binary. Q uesto's Q uestions 4.3 - Binary Calculations: 1a. Describe the terms ' most significant bit ' and ' flag '. [ 2 ] 1b. Using the terms from 1a , explain what an overflow error is. [ 2 ] 1c. Describe what is meant by an underflow error . [ 2 ] 2. Add together the following binary values. If an overflow error occurs you must state one has occurred. a. 010110012 and 010001012 [2 ] b. 110110112 and 010111012 [2 ] c. 001101102 and 011010112 [2 ] d. 110110112 and 010101112 [2 ] e. 011011012 and 110101102 [2 ] 3. Subtract the following binary values; put the first value on top of the second value: a. 100110102 and 000110002 [2 ] b. 110110112 and 010111012 [2 ] c. 011101102 and 011010112 [2 ] d. 110110112 and 010101112 [2 ] e. 111011012 and 110101102 [2 ] Watch on YouTube Watch on YouTube 4.2 Signed Binary Theory Topics 4.4 - Arithmetic Shift

Learn about the fundamentals of programming - selection, sequence and iteration. Also find out the difference between local and global variables and constants. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). Exam Board: OCR Specification: J277 2.1: Programming Fundamentals Watch on YouTube : Programming Fundamentals Sequence Selection Iteration Operators This section of the specification includes programming topics that are outlined in 1.2 (Designing Algorithms). You must have an understanding of a range of programming techniques , such as how to use selection , loops and operators . The best practice for learning is to try the tasks in the Python pages on this website (see the link to the right). Visit the Python section of CSNewbs ---> Programming Constructs There are three constructs ( ideas of programming ) that are used to control the flow of a program : Sequence Structuring code into a logical, sequential order . Selection Decision making using if statements . Iteration Repeating code using for or while loops . Variables Variables are used to store data in programs. They can be changed as the program runs . A variable has two parts - the data value such as "Emily" and an identifier such as First_Name . An efficient program will use variables with sensible identifiers that immediately state their purpose in the program. Using variable names like 'TotalNum' and 'Profit' rather than 'num1' and 'num2' mean that other programmers will be able to work out the purpose of the code without the need for extensive comments. Local & Global Variables Large programs are often modular - split into subroutines with each subroutine having a dedicated purpose. Local variables are declared within a specific subroutine and can only be used within that subroutine . Global variables can be used at any point within the whole program . Local variable advantages Saves memory - only uses memory when that local variable is needed - global variables use memory whether they are used or not. Easier to debug local variables as they can only be changed within one subroutine. You can reuse subroutines with local variables in other programs. Global variable advantages Variables can be used anywhere in the whole program (and in multiple subroutines). Makes maintenance easier as they are only declared once. Can be used for constants - values that remain the same. Constants π As specified before, a variable is data that can change in value as a program is being run. A constant is data that does not change in value as the program is run - it is fixed and remains the same. An example of a constant in maths programs is pi - it will constantly remain at 3.14159 and never change. Operators Comparison Operators Comparison operators are used to compare two data values . A table of common comparison operators used in programs are below: Arithmetic Operators Arithmetic operators are used to mathematically manipulate values . The most common arithmetic operators are add (+ ), subtract (- ), multiply (* ) and divide (/ ). Further arithmetic operators are shown below: Modulo division (also known as modulus ) reveals the remainder from the last whole number . For example: 9 % 4 = 1 (4 goes into 9 twice (8) with a remainder of 1) Integer division (also known as quotient ) reveals the ‘whole number of times ’ a number can be divided into another number : 9 // 4 = 2 (4 goes into 9 fully, twice) The symbol ^ represents exponentiation . However, Python uses ** to represent exponentiation. For example '2^3 = 8' is equivalent to '2³ = 8'. Logical Operators Logical operators typically use TRUE and FALSE values which is known as Boolean . You can find more information about Boolean values in section 4.1 . Q uesto's Q uestions 2.1 - Programming Fundamentals: Programming Constructs 1. Describe and draw a diagram for the 3 programming constructs . [6 ] Variables 1. What is the difference between local and global variables ? [4 ] 2. Describe two advantages of using local variables . [2 ] 3. Describe two advantages of using global variables . [2 ] 4. What is a constant ? Give an example . [2 ] 1.3 - Searching & Sorting Theory Topics 2.2 - Data Types

Learn about different input and output devices, RAM (random access memory) and ROM (read only memory) and storage devices, including solid state, magnetic and optical types. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 1.3 - Input, Output & Storage Specification: Computer Science H446 Watch on YouTube : Input & output devices Storage devices RAM & ROM Virtual storage This topic covers the internal and external devices required to input data into computer systems , output from them and store data for both temporary and long-term use . Input & Output Devices Input devices , such as a keyboard , mouse , microphone or sensor , allow data to be entered into a computer system for processing . Input can be manual (e.g. typing on a keyboard ) or automatic (e.g. a temperature sensor taking readings ). Output devices , such as monitors , printers and speakers , present the results of processing in a form understandable to humans . Input and output are not limited to text - they may also be visual , audio or tactile (e.g. braille displays or printed paper ). Storage Devices Secondary storage is non-volatile storage used to permanently hold programs and data when not in use by the CPU . There are three types : Magnetic storage uses magnetised patterns on a disk or tape (e.g. hard disk drives or magnetic tape ) to store large amounts of data for a low cost per gigabyte . Solid-state storage uses flash memory with no moving parts (e.g. SSDs and USB drives ), making it very fast , durable and portable . Because there are no moving parts, it is the fastest to access data . Optical storage uses lasers to read and write data as pits and lands on a disc surface (e.g. CDs, DVDs, Blu-ray). Discs are cheap to mass produce , but they are not durable , slow to access and have a low capacity . RAM & ROM Primary storage is low-capacity , internal storage that the CPU can directly access . There are two types: Random Access Memory (RAM ) is volatile storage that temporarily holds both programs and data currently in use , including the operating system . It can be read from and written to , but all contents are lost when the power is turned off . Read Only Memory (ROM ) is non-volatile storage that normally cannot be changed . The contents of ROM are saved when the power is turned off . ROM stores the BIOS and firmware , including the instructions needed to boot the computer when it is switched on . Virtual Storage Virtual storage is the separation of logical storage from physical storage , such as when data is stored remotely and accessed over a network instead of being kept locally . A common example is cloud storage , where data is held on remote servers and accessed via the internet . Benefits are that it is scalable , enables easy collaboration , provides automatic backup and saves local storage space . Drawbacks include that it relies on a stable internet connection , poses security risks and reduces user control over data . Q uesto's K ey T erms Input & Output Devices Secondary Storage: magnetic, solid state, optical, portability, capacity, cost (per GB), access speed, reliability, durability, power consumption Primary Storage: RAM, ROM, volatile, non-volatile Virtual Storage: cloud storage D id Y ou K now? The first commercial hard disk drive , the IBM 305 RAMAC (released in 1956 ), was the size of two fridges , weighed around a tonne , and stored just 5 MB of data - about the same as one .mp3 song . 1.2 - Types of Processor A-Level Topics 2.1 - Systems Software

Learn about things to consider when trying to make a good impression at work, including written, verbal and physical considerations. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 4.1 - Communication Skills Exam Board: OCR Specification: 2016 - Unit 1 Communication skills are vital for anybody working within the IT industry. Employees will need to communicate with other members of their team and with those who encounter issues with their computer systems. Interpersonal Skills Communication is not just through speaking to another person, behaviour is also important. Employees should sit up straight in their chairs to show interest and eye contact should be maintained when speaking to another person or listening in a meeting. It is important to speak clearly so that others can understand what you are trying to say. Verbal Communication Employees should know when to use informal and formal language appropriately. For example, formal language should be used in meetings as it is a work environment . Employees should think carefully about when to use technical terms . Technical terminology should be used when discussing issues with technicians but simplified explanations should be given to customers who may be inexperienced with their systems. Questioning Techniques Questioning is used to uncover problems in order to solve them . Closed questions will be direct and prompt a short, often one-word answer, such as "How many times have you tried to log in?". Open questions don't have an obvious answer and may elicit an opinion , such as "Why are you using Internet Explorer instead of Google Chrome?". Avoid leading questions - where you expect a certain response from the answerer, such as "Is the system always this slow?" Written Communication Again this form of communication can be formal - such as a letter to apply for a job - or informal - like sending a text or instant message to a team member. There are a number of considerations to take before deciding whether communication should be formal or informal. For example, if the communication is between peers or external agencies (such as other companies or customers), any policies the organisation has in place and whether the communication will be legally recorded (such as saving all email correspondence). Barriers to Communication There are several reasons why communication between people may be received or understood incorrectly . For example, noise in the room , language (this could be different spoken languages or the use of difficult technical terms ) and impairments (such as a hearing or visual impairment ). Another barrier is distraction - an email may be delayed because an employee is distracted by social media or other co-workers. Phones should also be turned off or silent during meetings. Q uesto's Q uestions 4.1 - Communication Skills: 1. Describe 3 interpersonal actions that an employee should follow when speaking or listening to other team members. [ 3 ] 2. Explain when an employee should use technical terms and when they should simplify their explanations . [ 4 ] 3. Describe the difference between closed , open and leading questions , giving an example of each. [6 ] 4. Describe 3 things that should be considered when deciding between formal or informal written communication . [3 ] 5. Describe 3 different barriers to successful communication . [3 ] 3.5 - Business Systems Topic List 4.2 - Communication Technology