Learn about input and output devices used with computer systems. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 1.1 - Computer Hardware Exam Board: OCR Specification: 2016 - Unit 1 Input Devices An input device allows data, such as text, images, video or sound, to be entered into a computer system. Common input devices: Mouse Keyboard Scanner Controller Microphone Webcam Chip Reader OCR / OMR Scanner Barcode Scanner Graphics Tablet Sensors (e.g. light or temperature) Touch Screen Remote Control Biometric Scanner (e.g. fingerprint or iris) Concept Keyboard Output Devices There are many outputs created by a computer system, including printed documents, on-screen data and sound. Common output devices: Monitor Printer (e.g. inkjet or laser) Plotter Speakers Projector Alarm Light Headphones Touch Screen Braille Terminal Communication devices can be found in 1.5 . Biometric Devices A biometric device uses a human characteristic as part of its security mechanism, such as a fingerprint , iris (eye), face o r voice . Organisations using biometrics must instruct each employee to first input their information to a database , by scanning their fingerprint for example. Whenever the scanner scans a finger it searches in its database to see if the fingerprint matches one that it already holds . Only authorised employees will have already scanned their fingerprints so if there is no match then access is not allowed . Advantages of biometric devices: Security is improved as biometrics can't be shared like passwords can. Even if a password is exposed the system can't be accessed without having the biometric too. Biometric scanners verify that a user is who they claim to be. Using a biometric device (e.g. fingerprint scanner) might be quicker and easier than entering a username and password. Disadvantages of biometric devices: Can be expensive to install and all users must take the time to initially set up by entering their biometric into the database so they will be recognised by the system. Unreliable in that it can be affected by the environment (e.g. dirty fingers can't be used with a fingerprint scanner or voice recognition may not work in a loud environment). Disabled users might not be able to provide the biometric required. Privacy concerns - users might not want their personal characteristics stored on a computer system. Q uesto's Q uestions 1.1 - Computer Hardware: 1. Make a list of 5 input devices and 5 output devices . Challenge yourself to look up and include devices from this page you may not be familiar with. [10 ] 2a. State 3 human features that may be recorded by a biometric device . [3 ] 2b. Describe how a biometric device works . [3 ] 2c. A school is considering installing biometric devices to allow only sixth form students to enter certain parts of the school. Describe 3 advantages and 3 disadvantages to the school of using biometrics in this way. [10 ] Topic List 1.2 - Computer Components

Learn about the characteristics of networks, protocols, standards, the internet, TCP/IP stack, DNS servers, protocol layering, LANs, WANs, packet and circuit switching, network security and threats, firewalls, proxies, encryption, network hardware, client-server and peer to peer networks. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 3.3 - Networks Specification: Computer Science H446 Watch on YouTube : Purpose of networks (LAN & WAN) Protocols & standards Protocol layering & TCP/IP stack Domain Name System (DNS) Packet & circuit switching Network security threats Network security protection Network hardware Client-server & peer-to-peer This topic looks at how data is transferred between computer systems on networks , including the required devices , protocols , network types and potential security threats . Purpose of Networks A network is a group of connected computers that can share data , resources and communicate with each other . The main purpose of a network is to allow users to share files , hardware (like printers ), internet connections and other services efficiently . A Local Area Network (LAN ) covers a small geographical area , such as a single building or school , and is usually owned and managed by one organisation . A Wide Area Network (WAN ) covers a large geographical area , connecting multiple LANs through public or leased communication lines such as the internet . Protocols & Standards Protocols are sets of rules that define how data is transmitted and received over a network , ensuring that devices can communicate reliably . Standards are agreed specifications that ensure different hardware and software systems are compatible and can work together . They are needed so that networks remain interoperable , secure and efficient , regardless of the devices or manufacturers involved . Common network protocols include: HTTP /HTTPS is used for transferring web pages over the internet . FTP aids the transfer of files across a network . SMTP is used to send emails and IMAP /POP receive emails . TCP/IP is the core suite of protocols that controls how data is packaged , addressed , transmitted and received across networks . Protocol Layering & TCP/IP Stack Protocol layering is used to divide complex networking tasks into manageable sections , making systems easier to design , understand and troubleshoot . It also allows different technologies or protocols to work together , as each layer only interacts with the ones directly above and below it. The four layers are: Application layer : Provides network services to end users , such as web browsing (HTTP ) or email (SMTP ). Transport layer : Manages data transmission between devices, ensuring it arrives reliably and in the correct order (e.g. TCP , UDP ). Internet layer : Handles addressing and routing of data packets between networks using IP (Internet Protocol ). Link layer : Manages the physical connection between devices and controls how data is transmitted over the network hardware . Domain Name System (DNS) The Domain Name System ( DNS ) translates human-readable domain names (like www.csnewbs.com ) into IP addresses that computers use to identify each other on a network . When a user enters a web address , the request is sent to a DNS server to find the matching IP address . If the server doesn’t have it stored locally , it queries other DNS servers higher in the hierarchy until it finds the correct address . The IP address is then returned to the user’s device , allowing it to connect to the correct web server to access the requested web page . Packet & Circuit Switching Packet switching and circuit switching are methods of data transmission , describing how data is sent across a network from one device to another . With packet switching , data is split into small packets , each sent independently across the network and reordered at the destination . This makes efficient use of network resources and allows many users to share the same connections . However, packets can arrive out of order or be delayed , causing variable performance . With circuit switching , a dedicated communication path is established between two devices for the duration of a session , as in traditional phone networks . It provides a reliable and consistent connection with guaranteed bandwidth . The drawback is that it wastes resources , as the dedicated line cannot be used by others . Network Security Threats There is a range of potential threats associated with network use to be aware of, including the following: Hackers can attempt to gain unauthorised access to computer systems or networks , often to steal , alter or destroy data . Viruses are malicious programs that attach themselves to other files and spread , potentially damaging or deleting data . Denial of Service ( DoS ) attacks overload a network or website with traffic , making it unavailable to legitimate users . Spyware secretly monitors user activity and collects information such as passwords or browsing habits . An SQL injection involves inserting malicious SQL code into a database query to access or alter sensitive data . Phishing uses fraudulent emails or messages to trick users into revealing personal information . Pharming redirects users from legitimate websites to fake ones designed to steal login details or financial information . Network Security Protection Minimising or preventing network threats is vital and can be achieved with the following measures : Firewalls monitor and control incoming and outgoing network traffic , blocking unauthorised access while allowing safe communication . Secure passwords help protect user accounts by making it difficult for attackers to guess or crack them, especially when they are long and complex . Anti-virus software scans and removes malicious programs , such as viruses and worms , before they can damage files or systems . Anti-spyware software detects and removes spyware , preventing it from secretly collecting personal or sensitive information from a user’s device . Network Hardware A range of network hardware is required for devices to transfer data to another location , including the following: A modem converts digital data into analogue signals and back , allowing internet access over phone or cable lines . A router directs data between networks and assigns IP addresses to connected devices . Cables provide the physical connections between devices . A Network Interface Card ( NIC ) enables a computer to connect to a network . A Wireless Access Point ( WAP ) allows wireless devices to join a wired network via WiFi . On a local area network ( LAN ), hubs broadcast data to all devices , whereas switches send data only to the intended destination , improving network efficiency . Client-Server & Peer-to-Peer A client–server network has a central server that provides resources and services to client computers . It allows for centralised management , making it easier to back up data and enforce security policies . However, it relies heavily on the server - if it fails , users may lose access to resources . A peer-to-peer (P2P ) network has no central server ; instead, each computer can act as both a client and a server , sharing resources directly . It is cheap and easy to set up , making it suitable for small networks . The drawback is that it can be less secure and harder to manage , as data and security depend on individual users . Q uesto's K ey T erms Purpose of networks: local area network (LAN), wide area network (WAN) Protocols: protocol, standard, protocol layers, TCP/IP stack, application layer, transport layer, internet layer, link layer DNS: Domain Name System Switching: packet switching, circuit switching Network security: hackers, viruses, unauthorised access, denial of service, spyware, SQL injection, phishing, pharming, firewalls, secure passwords, anti-virus, anti-spyware Network hardware: modem, router, cable, NIC, Wireless Access Points, hub, switch Client-server & peer-to-peer D id Y ou K now? The first computer worm is considered to be Creeper (in 1971 ), which spread across ARPANET computers and displayed the message: “ I’m the creeper, catch me if you can! ”. A second program called Reaper was then created to delete Creeper , making it arguably the first antivirus . 3.2 - Databases A-Level Topics 3.4 - Web Technologies

The Greenfoot homepage on CSNewbs with links to creating your own Greenfoot game from scratch, as well as key code and how to solve common errors. This section is aimed at the Eduqas GCSE 2016 specification. Links: Installing Greenfoot Greenfoot Game Tutorial Glossary of Key Code Help with Errors I'm Greta the Gecko and I'm here to teach you Greenfoot.

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 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 ➡

A list of programming topics including HTML, Greenfoot, Python. All Programming Topics Python HTML Greenfoot Assembly Language App Inventor 2

Learn about the eight roles of an operating system including CPU management, security, managing interrupts and the user interface. Based on the 2020 Eduqas (WJEC) GCSE specification. 6.1: Operating Systems Exam Board: Eduqas Specification: 2020 What is an Operating System? An operating system (OS ) is software that helps to manage the resources of a computer system . There are eight main roles of an operating system: Manage the CPU A critical role of the OS is to manage the CPU so that applications and processes can be run efficiently . The CPU is effectively managed by performing three further roles: Manage Memory (RAM) The OS reserves memory space in RAM for stored programs to be copied into. The FDE cycle is executed continuously to carry out the instructions. The OS also ensures that programs are appropriately managed so that data is stored in correct memory locations and not corrupted . Manage Interrupts A interrupt is an alert signal sent to the CPU when an application or hardware device requires immediate attention . The OS must efficiently manage interrupts so that a problem can be dealt with quickly if one occurs. Manage Multi-Tasking The OS manages tasks so instructions can be executed by the CPU in turn - this is called scheduling . The OS prevents processes from interfering with others and crashing. Tasks should appear to run simultaneously even though only one process can be executed at a time. Manage Backing Store The backing store is another term for secondary storage devices such as the magnetic hard disk drive , optical drives or solid state memory sticks. The OS ensures data is stored correctly and can be efficiently retrieved from the backing store. Files are organised in a hierarchical (logical) structure . Manage Peripherals A peripheral is an external device connected to a computer system to input or output data . The OS manages the receiving of data from input devices (such as a keyboard or mouse) and the transfer of data to output devices (such as a monitor or speaker). Manage Security The OS allows users to create, manage and delete accounts with different permissions. It also permits multiple users to log in and change passwords . Antivirus and firewall software is managed by the OS as well as some data encryption processes. Manage the User Interface The final function of an operating system is to provide a user interface , allowing a human to interact with the computer system . The way in which a user can navigate a computer system is known as human-computer interaction ( HCI ). Graphical User Interface (GUI) The most common type of user interface is a graphical user interface (GUI ) which can be presented in the following ways: Icons are displayed to represent shortcuts to applications and files. Multiple windows can be opened at the same time and switched between. A folder and file system is displayed and manipulated allowing for copying , searching , sorting and deleting data. The interface can be customised , such as changing font sizes and the desktop background . The taskbar allows shortcuts to be pinned for quick access . Menus can be opened from the Start button to display files and shortcuts. System settings can be accessed such as network and hardware options . Q uesto's Q uestions 6.1 - Operating Systems: 1. Describe each role of the operating system : 1. Manage the CPU [ 2 ] 2. Manage memory [ 2 ] 3. Manage interrupts [ 2 ] 4. Manage multi-tasking [ 2 ] 5. Manage backing store [ 2 ] 6. Manage peripherals [ 2 ] 7. Manage security [ 2 ] 8. Manage the user interface [ 2 ] 2. Describe 5 different ways the operating system can provide a graphical user interface (GUI) . [5 ] 3. Describe two advantages and two disadvantages of using the following types of human-computer interaction (HCI) : a. Command-Line interface [ 4 ] b. Touch-Sensitive interface [ 4 ] c. Menu-Driven interface [ 4 ] d. Voice-Driven interface [ 4 ] Command-Line Interface Other types of user interface do exist, such as a command-line interface (CLI ). This type of interface is entirely text-based and requires users to interact with the system by typing commands . This is a complicated process and mistakes could easily accidentally delete data. There are many commands to learn so only experts who have been trained t o learn this interface will be able to efficiently make use of it. Menu-Driven Interface A menu-driven interface displays data in a series of linked menus . Examples include cash machines (ATMs) and old iPods . This type of interface is generally user friendly and easy to use as commands do not need to be memorised. However it can be annoying to find specific data through a large number of menus without a search feature. Touch-Sensitive Interface Another type of user interface is a touch-sensitive interface , used with smartphones and tablets . A human interacts with the device by pressing on a touchscreen , making it very intuitive and suitable for most users without training. Touch-sensitive interfaces may not work with dirty or wet fingers and it will take longer to write text compared to using a keyboard. Voice-Driven Interface A voice-driven interface can be controlled by speaking commands aloud to a listening device. Examples include Amazon's Alexa devices, Apple's Siri technology and Google Home . This interface is intuitive , can be used hands-free and helps to speed up processes . However commands may be misheard or limited in what can be performed. 5.1 - Data Structures Theory Topics 6.2 - Utility Software

Learn about the three factors that affect computer performance - cache memory, clock speed and the number of cores. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 1.2: CPU Performance Exam Board: Cambridge OCR Specification: GCSE - J277 Watch on YouTube : CPU Performance How these CPU characteristics affect the performance of a computer system: Clock speed Cache size Number of cores What You Need to Know Clock Speed A computer has a component called a clock , which produces regular electrical pulses . Clock speed is the number of clock pulses the CPU receives per second . It is measured in gigahertz (GHz ). For example, 3.5 GHz is 3.5 billion pulses per second . The Control Unit (CU ) uses each clock pulse to send control signals that coordinate operations within the computer. A higher clock speed improves the performance of the CPU because more fetch-execute cycles can be completed per second . This means more instructions can be executed in the same amount of time , so tasks can be completed faster . Cache Size Cache memory is fast , temporary storage inside (or very close to) the CPU , which stores frequently accessed data and instructions . It is typically split into three levels (L1 , L2 and L3 ), with each level generally being larger but slower than the previous level. As data and instructions are fetched during the fetch-execute cycle , frequently accessed data and instructions can be stored in cache , reducing the need to repeatedly fetch them from RAM, which is slower to access . A CPU with a larger cache can store more frequently accessed data and instructions , improving performance because they can be accessed faster from cache than from RAM . Number of Cores Some CPUs have multiple cores . A core is an individual processing unit within the CPU , containing components such as a control unit , ALU , registers and cache . Each core can independently perform the fetch-execute cycle . A CPU with more cores can have higher performance because it can process more instructions at the same time . However, performance may not improve if one core must wait for another to complete its task . Also, some software is not designed to use multiple cores , so it will not benefit from having additional cores . Single-core Dual-core Quad-core Octa-core Q uesto's Q uestions 1.2 - CPU Performance: Clock Speed 1a. What is clock speed ? What is it measured in? [ 2 ] 1b. Explain how a higher clock speed improves performance . [ 2 ] Cache Size 2a. What is cache memory ? [ 2 ] 2b. Describe why a larger c ache size may mean performance is higher . [ 4 ] Number of Cores 3a. What is a core ? [ 2 ] 3b. Explain why a quad-core processor should have a higher performance than a dual-core processor . [ 3 ] 3c. Explain two reasons why having more cores doesn't necessarily mean the performance will be better . [ 2 ] 1.1b - Fetch-Execute Cycle 1.3 - Embedded Systems Theory Topics

Learn about how communication skills contribute to software application development, including verbal, written and questioning techniques. Based on Unit F160 (Fundamentals of Application Development) for the OCR Cambridge Advanced National 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) 6.2 - Communication Skills Watch on YouTube : Communication skills Developers working to create applications must be able to effectively communicate with team members , clients and users in a range of different ways . There are five communication skills you need to know: appropriate language , verbal , non-verbal , questioning techniques and written communication . You need to be aware of how each communication skill contributes to software application development and when they would be used appropriately by various job roles and in different stages of application development . Communication Skills Forms of Communication Appropriate language must be used to meet the needs of the audience by tailoring vocabulary , tone and technical detail to suit the client . Non-verbal communication includes body language , facial expressions , gestures , posture , eye contact and appearance . Question techniques have different goals , such as probing questions being used to explore detail and clarifying questions to check understanding . Verbal communication relates to spoken words and includes articulation , tone and pace , but also listening skills . Written communication is through emails , reports , documentation , messages and comments . It requires clarity , accuracy and professionalism . Q uesto's Q uestions 6.2 - Communication Skills: 1. Give examples of when written communication would be used in application development and by which job roles . [3 ] 2. Describe four different types of questions , with an example of each that relates to application development . [4 ] 3. Explain why effective non-verbal communication is important in application development . [ 3 ] Studies estimate that adults ask about 30 questions a day , whereas 4-year-olds ask on average 300 questions a day . D id Y ou K now? 6.1 - Job Roles Topic List

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 lossy and lossless compression and the lossless compression algorithms run-length encoding and dictionary coding. This topic also covers symmetric and asymmetric encryption and the uses of hashing. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 3.1 - Compression, Encryption and Hashing Specification: Computer Science H446 Watch on YouTube : Lossy & Lossless Compression Lossless Compression Algorithms Encryption Hashing Lossy vs Lossless Compression Compression is the process of reducing the size of a file so it takes up less storage space and can be transmitted more quickly over a network . It works by encoding data more efficiently or removing unnecessary information . Benefits of compression include faster file transfer speeds , reduced storage requirements and improved performance when streaming data . Lossy compression permanently removes some data that is less important to human perception , such as subtle sounds or image details , resulting in smaller file sizes but slightly lower quality . Lossless compression reduces file size without losing any data , allowing the original file to be perfectly restored after it is decompressed . Lossless Compression Algorithms There are two types of lossless compression that you need to know: Run-Length Encoding (RLE ) is a simple form of lossless compression that reduces file size by storing repeating data as a single value and a count . For example, a sequence like AAAAABBBCCCC could be stored as A5B3C4 , saving space in files with many repeated elements , such as pixels in images . Dictionary Encoding replaces repeating patterns of data with shorter codes that reference entries in a dictionary . The dictionary stores common sequences once , and each repetition is replaced by a shorter reference , making it efficient for text and other data with recurring patterns . Encryption Encryption is the process of converting readable data (plaintext ) into an unreadable form (ciphertext ) to prevent unauthorised access . It ensures the confidentiality and security of information during storage or transmission . Symmetric encryption uses the same key for both encryption and decryption , meaning the sender and receiver must share the key securely . It is fast and efficient, but key distribution is a major risk if the key is intercepted . Asymmetric encryption uses a pair of keys - a public key for encryption and a private key for decryption . It is more secure for communication and vital for confidential uses such as banking . Hashing Hashing is the process of applying a mathematical function (hash function ) to data to produce a fixed-size value , known as a hash . It is a one-way process , meaning the original data cannot be reconstructed from the hash . Hashing is commonly used for data integrity checks , password storage and digital signatures . Even a tiny change in the input data produces a completely different hash , making it useful for detecting tampering or corruption . Q uesto's K ey T erms D id Y ou K now? Compression: lossy compression, lossless compression, run-length encoding, dictionary encoding Encryption: plaintext, ciphertext, key, symmetric encryption, asymmetric encryption Hashing: hash function, hash Alan Turing and his team used pattern recognition to analyse recurring sequences in encrypted German messages , helping to break the Enigma code , which was a major factor in the Allies’ victory in World War II . 2.4 - Programming Languages A-Level Topics 3.2 - Databases

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