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Learn about the six parts of a data packet and how packet switching works. Based on the 2020 Eduqas (WJEC) GCSE specification. 3.2: Data Packets & Switching Exam Board: Eduqas / WJEC Specification: 2020 + What is a data packet? 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. Contents of a Data Packet Data packets contain six distinct pieces of data which are used to redirect the packets towards the destination address. Packet Switching vs. Circuit Switching The key difference is that a circuit-switched network sends data along the same route . A packet-switched network sends data packets along different routes . Packet Switching With a packet-switched network the data is split into packets . The data packets are transmitted over a network and may take different routes to its destination. When all the packets have arrived the data is reassembled . The Internet is an example of a packet-switching network. Advantages of Packet Switching: Transmission is more secure as it is harder for a hacker to intercept complete data because it can take different routes . If a network device fails the data packets can take an alternative route . Data packets can be sent efficiently and individually across less busy routes . Disadvantages of Packet Switching: Reassembling the data takes longer because packets may arrive out of order . It is less reliable than circuit switching as some data packets may not reach the destination (this is called packet loss ). Circuit Switching When data is transmitted over a circuit-switched network all of the data takes the same route to the destination address in one continuous stream . The data is quickly reassembled at the destination because it is already in the correct order . The old telephone system is an example of a circuit-switched network. Advantages of Circuit Switching: Reassembling the data is quick because the packets arrive in the order that they were sent. It is more reliable than packet-switching because data is sent in one continuous stream . The transmission is fast and should encounter fewer errors - once the connection has been securely established . Disadvantages of Circuit Switching: Less secure as hackers could intercept the data and more easily access the data as it all takes the same route. Establishing a connection takes time to set up. If any device fails on the route then the whole connection breaks and data transfer will be incomplete. Q uesto's Q uestions 3.2 - Data Packets & Switching: 1. Draw the data packet diagram and label all 6 pieces of information . [ 6 ] 2a. Describe how packet switching works . [3 ] 2b. Describe the advantages of packet switching . [3 ] 2c. Describe the disadvantages of packet switching . [2 ] 3a. Describe how circuit switching works . [3 ] 3b. Describe the advantages of circuit switching . [3 ] 3c. Describe the disadvantages of circuit switching . [3 ] 3.1 - Network Characteristics Theory Topics 3.3 - Network Topology

Learn about the different protocols used on networks - HTTP, HTTPS, TCP, IP, Ethernet, WiFi, FTP and SMTP. Based on the 2020 Eduqas (WJEC) GCSE specification. 3.5: Protocols Exam Board: Eduqas / WJEC Specification: 2020 + What is a protocol? A protocol is a set of rules that allow devices on a network to communicate with each other . TCP / IP is actually two separate protocols that combine together. TCP / IP (Transmission Control Protocol / Internet Protocol) TCP is a protocol that allows packets to be sent and received between computer systems. It breaks the data into packets and reassembles them back into the original data at the destination. IP is a protocol in charge of routing and addressing data packets . This ensures data packets are sent across networks to the correct destination . It is also an addressing system - every device on a network is given a unique IP address so data packets can be sent to the correct computer system. HTTP is used to transfer web pages over the Internet so that users can view them in a web browser . All URLs start with either HTTP or HTTPS (e.g. https://www.csnewbs.com). HTTPS is a more secure version of HTTP that works with another protocol called SSL ( Secure Sockets Layer ) to transfer encrypted data . You should see a padlock symbol in the URL bar if your connection to that website is secure. HTTP/HTTPS (Hypertext Transfer Protocol) Ethernet is a protocol for wired connections . Ethernet is used at both the data link and physical layers to describe how network devices can format data packets for transmission. WiFi is the main standard for wireless connections . WiFi is actually a brand name that uses a protocol called IEEE 802.11 . Another wireless standard is Bluetooth , for short-range data transfer. Connection Protocols Transfer Protocols FTP ( File Transfer Protocol ) is used to transfer files across a network. It is commonly used to upload or download files to/from a web server . SMTP ( Simple Mail Transfer Protocol ) is a protocol used to send emails to a mail server and between mail servers . Q uesto's Q uestions 3.5 - Protocols: 1. Describe each of the following protocols . It might be helpful to also draw an icon or small diagram for each one: a. TCP [ 2 ] b. IP [ 2 ] c. HTTP & HTTPS [ 3 ] d. WiFi (802.11) [ 1 ] e. Ethernet [ 2 ] f. FTP [ 2 ] g. SMTP [ 2 ] 2. State which protocol would be used in the following scenarios : a. Transferring a music file to a friend over the internet. [ 1 ] b. Sending an email to a family member in America. [ 1 ] c. Using a wireless connection to play a mobile game. [ 1 ] d. Using a webpage to enter a password securely. [ 1 ] e. Watching a video on YouTube. [1 ] 3.4 Network Hardware & Routing Theory Topics 3.6 - 7 Layer OSI Model

Based on the OCR Computer Science A-Level 2015 specification. Exam Board: OCR 3.1a - Compression Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 3.1a - Compression: 1. What is cache memory ? [ 2 ] 2.4c - Object-Oriented Language Theory Topics 3.1b - Encryption & Hashing

Learn about how images are represented in a computer system, including file size, resolution, colour depth and metadata. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 2.4d: Image Storage Exam Board: OCR Specification: J277 Watch on YouTube : Pixels & Resolution Colour Depth & Metadata Image File Size Bitmap Images Bitmap images are made of pixels - single-colour squares - arranged on a grid . Each pixel is assigned a binary value which represents the colour of that pixel. The quality of a bitmap image depends on the total amount of pixels , this is known at the image resolution . Because it is made of pixels, scaling a bitmap image up will result in a visible loss of quality . Most images on computers are bitmaps, such as photos and screenshots . Vector Images Vector images are drawn by the computer following precise mathematical instructions to create lines and objects . Vectors are usually smaller in file size compared to bitmaps because each pixel in a bitmap is stored as an individual binary value. Vectors can be scaled up without any loss of quality and are typically used for logos and animations . How to Calculate the File Size of a Bitmap File Size = Resolution x Colour Depth The resolution of an image is the width in pixels multiplied by the height in pixels. The colour depth (also known as bit depth ) is the number of bits that are used to represent each pixel's colour . 1 bit represents 2 colours (0 or 1 / black or white). 2 bits will allow for 4 colours, 3 bits for 8 colours, 4 for 16 etc. A colour depth of 1 byte (8 bits ) allows for 256 different colours . Remember you must multiply the colour depth , not the number of available colours (e.g. 8 not 256). The RGB (Red , Green , Blue ) colour model uses 3 bytes (a byte of 256 red shades , a byte of 256 green shades and a byte of 256 blue shades ) that together can represent 16.7 million different colours. Example Height = 6 bits Resolution = height x width Resolution = 8 x 6 = 48 bits -------------------------- Colour Depth = 1 bit (only 2 colours) -------------------------- File Size = Resolution x Colour Depth File Size = 48 x 1 = 48 bits File Size in bytes = 48 ÷ 8 = 6 bytes File Size in kilobytes = 6 ÷ 1000 = 0.00 6 kilobytes Width = 8 bits Look carefully at the exam question to see if the examiner is expecting the answer in bits, bytes or kilobytes . Always calculate the file size in bits first then: Divide the file size in bits by 8 to convert to bytes . Divide the file size in bytes by 1000 to convert to kilobytes . Metadata for Images Metadata is additional data about a file . Common image metadata includes: Height and w idth in pixels Colour depth Resolution Geolocation Date created Last edited File type Author details Metadata is important, For example, the dimensions must be known so the image can be displayed correctly . Metadata for a picture taken on a smartphone: width in pixels, e.g. 720 height in pixels, e.g. 480 Q uesto's Q uestions 2.4d - Image Storage: 1. Describe three ways that bitmap and vector images are different. [ 6 ] 2. Define the terms image resolution and colour depth . [2 ] 3. How many colours can be represented with a colour depth of... a. 1 bit [ 1 ] b . 5 bits [ 1 ] c. 1 byte [ 1 ] 4. How is the file size of an image calculated? [2 ] 5a. An image file has a width of 10 pixels , a height of 8 pixels and a colour depth of 2 . What is the file size in bytes ? [3 ] 5b. An image file has a width of 120 pixels , a height of 120 pixels and a colour depth of 1 . What is the file size in kilobytes ? [3 ] 5c. An image file has a width of 32 pixels , a height of 21 pixels and a colour depth of 1 . What is the file size in bytes ? [3 ] 6. State what is meant by metadata and give three examples of metadata for a graphics file. [ 3 ] 2.4c - Character Storage Theory Topics 2.4e - Sound Storage

Learn about the seven steps of the fetch-decode-execute cycle and important registers in the CPU. Based on the 2020 Eduqas (WJEC) GCSE specification. 1.2: The FDE Cycle Exam Board: Eduqas / WJEC Specification: 2020 + The Fetch - Decode - Execute (FDE) cycle is performed by the CPU millions of times every second. This cycle is how the CPU processes data and instructions for each program or service that requires its attention. Important Registers A register is a small storage space for temporary data in the CPU . Each register has a specific role . There are five essential registers used in the FDE cycle : Program Counter (PC) A register that tracks the RAM address of the next instruction to be fetched . Memory Address Register (MAR) A register that tracks the RAM address of the instruction that is to be fetched . Memory Data Register (MDR) The MDR stores the instruction that has been transferred from RAM to the CPU . Current Instruction Register (CIR) A register that stores the instruction that has been fetched from RAM , and is about to be decoded or executed . Accumulator (ACC) The ACC stores the result of mathematical or logical calculations . Fetch - Decode - Execute Cycle The essential idea of the FDE cycle is that instructions are fetched from RAM , to be decoded (understood) and executed (processed) by the CPU . 1. The Program Counter (PC ) register displays the address in RAM of the next instruction to be processed . This value is copied into the Memory Address Register (MAR ). 0054 2. The PC register is increased by 1 . This prepares the CPU for the next instruction to be fetched. 0055 3. The CPU checks the address in RAM which matches the address held in the MAR . 0054 4. The instruction in RAM is transferred to the Memory Data Register (MDR ). 5. The instruction in the MDR is copied into the Current Instruction Register (CIR ). MDR MDR CIR 6. The instruction in the CIR is decoded (understood) and executed (processed). Any result of an execution is stored in the Accumulator (ACC ) register. CIR ACC 7. The cycle repeats by returning to the first step and checking the program counter for the address of the next instruction . Q uesto's Q uestions 1.2 - The Fetch - Decode - Execute (FDE) Cycle: 1 . What is the purpose of the registers ? [1 ] 2 . Describe the purpose of each register : a. The Program Counter (PC) [ 1 ] b. The Memory Address Register (MAR) [ 1 ] c. The Memory Data Register (MDR) [ 1 ] d. The Current Instruction Register (CIR) [ 1 ] e. The Accumulator (ACC) [ 1 ] 3. Draw a diagram of the seven steps of the Fetch - Decode - Execute cycle . [7 ] 1.1 - The CPU 1.3 - Primary Storage Theory Topics

Learn about the main character sets - ASCII (American Standard Code for Information Interchange) and Unicode. Also, discover the five data types - character, string, integer, real and Boolean. Based on the 2020 Eduqas (WJEC) GCSE specification. 4.5: Character Sets & Data Types Exam Board: Eduqas / WJEC Specification: 2020 + What is a Character Set? A character set is a table that matches together a character and a binary value . Character sets are necessary as they allow computers to exchange data . Two common character sets are ASCII and Unicode . ASCII Unicode ( American Standard Code for Information Interchange ) 0100 0001 0100 0010 0100 0011 Uses Binary 128 Tiny Set of Characters Less Memory Required Per Character U+0042 U+0055 U+004E Uses Hexadecimal 137,000+ Large Set of Characters More Memory Required per Character What are the different data types? When programming, variables should be given appropriate data types . Character String Integer A single character , such as a letter, number or punctuation symbol. Examples: A sequence of characters , including letters, numbers and punctuation. Examples: A whole number . Examples: T 8 ? Harry Waters 14:50pm Ice Age 4 475 -8432 56732 Real Boolean Telephone numbers are always stored as a string , not an integer. True / False Yes / No 0 / 1 An answer that only has two possible values . Examples: A decimal number . Examples: 65.3 -321.1234 909.135 Be careful with punctuation. 32.10 is a real but £32.10 is a string. Q uesto's Q uestions 4.5 - Character Sets & Data Types: 1. What is a character set and why are they needed ? [ 2 ] 2. Describe 3 differences between ASCII and Unicode . [6 ] 3. State the 5 different data types . [ 5 ] 4. State which data type is most suitable for the following variables: a. Age [ 1 ] b. Surname [ 1 ] c. Height (in metres) [ 1 ] d. First Initial [ 1 ] e. Phone number [ 1 ] f. Right-Handed? [ 1 ] 4.4 Arithmetic Shift Theory Topics 4.6 - Graphical Representation

Based on the OCR Computer Science A-Level 2015 specification. Exam Board: OCR 2.1b - Modularity & IDE Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 2.1b - Modularity & IDE: 1. What is cache memory ? [ 2 ] 2.1a - Recursion & Variables Theory Topics 2.2a - Computational Methods

Learn how to use mathematical operators in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 4b - Mathematical Operators Modulo Division The modulo operator - the percentage symbol % - will work out the remainder left over when one value is divided by another. print (30 % 6) = 0 30 ÷ 6 = 5, which is a whole number, so there is no remainder and 0 is output . print (30 % 7) = 2 30 ÷ 7 = 4 remainder 2 ; so the remainder is output . You can use modulo with variables too: num1 = 33 num2 = 4 print ( "The remainder is" , num1 % num2) The remainder is 1 = A common use of modulo is to check if a number is odd or even . If a number has no remainder when divided by 2 then it is even . = num = int ( input ( "Enter a number: " )) if num % 2 == 0: print (num, "is even." ) else : print (num , "is odd." ) Enter a number: 400 400 is even. Enter a number: 191 191 is odd. = Modulo Div i sion Task 1 ( Remainder) Ask the user to input a whole number . Use the modulo operator ( % ) to check if there is a remainder when the user's number is divided by 5 . Print the re mainder. Example solution: Enter a number: 123 The remainder when divided by 5 is 3 Modulo Div i sion Task 2 ( Rollercoaster) Use the odd/even program above to help solve this problem: A rollercoaster only lets people on in groups of 4 . Ask the user to input a number for how many people are in their group. Check if that number is directly divisible by 4 using modulo division ( % ). If it is then print “Perfect groups of four!” Else print “You will be split up” . Example solutions: Welcome to the Hyper Coaster! How many in your group? 6 You will be split up! Welcome to the Hyper Coaster! How many in your group? 12 Perfect groups of four! Integer Division Integer division removes any decimal numbers when performing division , leaving just the integer (whole number ). In Python integer division is performed using // . print (20 / 3) print (20 // 3) = 6.666666666666667 6 Integer Div i sion Task 1 ( Integer Division by 5 ) Use an input line with int to ask the user to enter a number . Use integer division ( // ) to divide the number by 5 without keeping any decimal values . Challenge: Improve your solution by altering the print line to be more user friendly . Example solutions: Enter a number: 27 5 Enter a number: 27 5 goes into 27 5 times. Integer Div i sion Task 2 ( Plane Rows) A large plane has 6 seats in each row. Input the number of passengers on the plane and use integer division to work out how many full rows will be filled. Example solution: How many passengers are there in total? 174 There will be 29 full rows on the plane. Exponent (Powers) An exponent is the number of times a value is multiplied by itself , for example 2 = 2 x 2 x 2 = 8 . The symbol to represent an exponent in Python is ** . For example: 4**2 represents 4 which is also 4 x 4 . 3 2 print (4**4) = 256 base = 5 exponent = 4 print (base**exponent) 625 = Exponent Task 1 ( Square Number) Use an input line with int to ask the user to enter a number . Output the square of this number. Example solution: Enter a number: 12 12 squared is 144 Exponent Task 2 ( Custom Exponent) Use an input line with int to ask the user to enter a number, this will be the base . Make another input line with int to ask for the exponent . Use ** between the base and the exponent and print it. Challenge: Make your solution better by including the base and exponent in the print line. Example solutions: Enter the base: 7 Enter the exponent: 3 343 Enter the base: 7 Enter the exponent: 3 7 to the power of 3 is 343 ⬅ 4a - If Statements 4 c - Log ical Operators ➡

Based on the OCR Computer Science A-Level 2015 specification. Exam Board: OCR 2.1a - Recursion & Variables Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 2.1a - Recursion & Variables: 1. What is cache memory ? [ 2 ] 1.1 - Computational Thinking Theory Topics 2.1b - Modularity & IDE

Learn how to add a counter to Greenfoot to keep track of the score. Learn how to add and subtract points to the counter. Part 6 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. 6. The Counter Greenfoot Tutorial 1. Import the Counter The counter class can be imported into your Greenfoot world. Select Edit in the main Greenfoot window then ' Import Class... ' and choose Counter . Watch on YouTube: The Counter class will appear in the Actor classes list . Right-click on the Counter, choose the ' new Counter() ' option and drag it into the world. Now right-click on the background and select 'Save the World' once you have dragged the counter into the world. 2. Increase the Counter by 1 Two lines of code are required to increase the counter . Add this code when your main character is removing the collectible object . This code allows your main character to access the 'add' method from the Counter class . The method 'add ' just increases the value of the counter by the number in the brackets . To decrease the counter , type a negative value in the brackets, such as -1 . < Part 5 - Play Sounds 3. Compile and Run Click the Compile button at the top of the code editor . Then you can go back to the main Greenfoot window and click Run to test if your counter increases . Click on me if you've got an error that you're stuck with. Part 7 - Extension Ideas >

A complete list of tags required for students to know how to use in the 2016 Eduqas GCSE specification. Follow the links on each tag to see how to use them. Here you can find a list of tags. Click a tag to see how to use it. Tags for Eduqas GCSE:

Based on the OCR Computer Science A-Level 2015 specification. Exam Board: OCR 4.1c - Signed Binary & Floating Point Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 4.1c - Signed Binary & Floating Point: 1. What is cache memory ? [ 2 ] 4.1b - Denary, Binary & Hexadecimal Theory Topics 4.1d - Binary Calculations