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Navigate between all Unit F160 (Fundamentals of Application Development) topics in the OCR Cambridge Advanced National in Computing (AAQ) specification. Qualification: Cambridge Advanced National in Computing (AAQ) Unit: F161: Developing Application Software Certificate: Computing: Application Development (H029 / H129) Unit F161: Developing Application Software These pages are based on content from the OCR Cambridge Advanced National in Computing (AAQ) specification . Unit F161 YouTube Playlist Topic 1: Application Software Considerations 1.1 - Application Platforms 1.2 - Devices 1.3 - Storage Locations This unit will be updated in summer 2026. Check here for the latest progress update. Topic 2: Data & Flow in Application Software 2.1 - Data Formats & Types 2.2 - Data Flow 2.3 - Data States Topic 3: API & Protocols 3.1 - Application Programming Interfaces (API) 3.2 - Protocols Topic 4: Application Software Security 4.1 - Security Considerations Topic 5: Operational Considerations 5.1 - Testing 5.2 - Types of Application Software Installation 5.3 - Policies Topic 6: Legal Considerations 6.1 - Legal Considerations

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

Learn about data types (integer, real, character, string, Boolean), positive and negative binary, denary, hexadecimal, sign and magnitude, two’s complement, binary addition, binary subtraction, normalisation of floating point numbers, floating point arithmetc, bitwise manipulation, masks (AND, OR, XOR) and character sets (ASCII, Unicode). Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 4.1 - Data Types Specification: Computer Science H446 Watch on YouTube : Data types Denary & binary Sign and magntiude Two's complement Binary addition Binary subtraction Hexadecimal & binary Hexadecimal & denary Floating point Floating point normalisation Floating point addition Floating point subtraction Binary shifts Masks (AND, OR, XOR) Character sets This is a mathematical topic that requires conversion between the binary , denary (decimal ) and hexadecimal number systems . Representing positive and negative binary values is included, as well as adding and subtracting binary numbers and using normalised floating point to represent decimal numbers . Data Types Data types are needed so that the computer knows how to store , process and interpret data correctly . They help ensure that only valid operations are performed on data . For example, you can add two numbers , but not a number and a word . Common data types: Integer : A whole number , e.g. 7 or -12 . Real : A decimal number , e.g. 3.14 or -0.5 . Boolean : A data type with only two possible values - True or False . Character : A single letter , digit or symbol , e.g. ‘k ’, ‘7 ’, or ‘? ’. String : A sequence of characters treated as text, e.g. “CSNewbs ”. Converting from one data type to another is called casting , e.g. age = str(age) would convert the variable age to a string in Python . YouTube video uploading soon Binary Binary is a base-2 number system with all values comprised only of 0 and 1 , e.g. 01011001 . Denary (also called decimal ) is the base-10 number system you grew up learning, with 10 possible values between 0 and 9 , e.g. 453 . Computers use binary because they are built from electronic components (transistors ) that have two states (on and off ), which are easily represented by 1s and 0s . All data processed and stored by the computer (e.g. numbers , text , images and sounds ) are represented in binary . To convert an 8-bit binary value to denary , write 128 - 64 - 32 - 16 - 8 - 4 - 2 - 1 above the binary and add together the values with a 1 underneath . For example, 10101101 is 173 (128 + 32 + 8 + 4 + 1 ). YouTube video uploading soon Storing Negative Numbers -183 Sign and Magnitude and Two’s Complement are two methods of representing negative numbers in binary . In Sign and Magnitude , the most significant bit (MSB ) represents the sign - 0 for positive and 1 for negative - while the remaining bits store the number’s magnitude (value ). For example, in 8-bit form, 0 101 0010 is +82 and 1 101 0010 is -82 . However, this method has two representations of zero (+0 and -0 ), which can cause problems and may give incorrect results if used to add or subtract . In Two’s Complement , negative numbers are represented by inverting all bits of the positive value and adding 1 to the result. This method has only one zero and makes binary addition and subtraction simpler . YouTube video uploading soon YouTube video uploading soon Binary Addition & Subtraction Binary addition works from right to left but only uses the digits 0 and 1 . The key rules are: 0 + 0 = 0 0 + 1 = 1 1 + 0 = 1 1 + 1 = 10 (write down 0 and carry 1 to the next left column ). 1 + 1 = 1 = 11 (write down 1 and carry 1 to the next left column ). If the final addition produces an extra carry bit , it may indicate an overflow error , if the result is too large to fit in the available bits . Binary subtraction can be done using borrowing , similar to denary subtraction , or more commonly by using two’s complement . In two’s complement subtraction , you add the negative version of one number (found by inverting the bits and adding 1 ) to the other to perform subtraction using binary addition rules . YouTube video uploading soon YouTube video uploading soon Hexadecimal 9E8A Hexadecimal is a base-16 number system using the digits 0 to 9 and the letters A to F, where A = 10 and F = 15 in denary . It’s often used in computing because it provides a shorter , more readable way to represent long binary values . For example, two hex digits represent eight binary bits , making conversions quick and efficient . To convert from binary to hexadecimal , split the binary number into groups of four bits (from right to left ) and convert each group into its hex equivalent . Example: 1101 0110 → 1101 (14 → D ) and 0110 (6 ) → D6 . To convert hexadecimal to binary , replace each hex digit with its 4-bit binary equivalent . Example: 2F → 0010 (2 ) and 1111 (15 → F ) → 0010 1111 . The easiest method to convert between denary and hexadecimal is to convert the value to binary first . Example: 26 → 0001 1010 → 1A . YouTube video uploading soon YouTube video uploading soon Floating Point Floating point is a way of representing real (decimal ) numbers in binary using a mantissa and an exponent . It allows computers to store a wide range of values efficiently , including very small and very large numbers . Floating point normalisation means adjusting the number so that the mantissa begins with a 01 (if it is positive ) or 10 (if it is negative ). This ensures the representation is unique and uses all available bits in the mantissa for precision . To add or subtract floating point numbers , the exponents must first be made equal by shifting the mantissa of the smaller number . Once aligned , the mantissas are added or subtracted , and the result is then normalised again to maintain the correct form . YouTube video uploading soon YouTube video uploading soon Binary Shifts A binary shift moves all the bits in a binary number left or right by a set number of places . A left shift moves all bits to the left , filling the empty right-hand bits with zeros . Each left shift multiplies the number by 2 . For example, shifting 0001 0100 (20 ) one place left gives 0010 1000 (40 ). A right shift moves all bits to the right , discarding the rightmost bits . Each right shift divides the number by 2 . For example, shifting 0010 1000 (40 ) two places right gives 0000 1010 (10 ). YouTube video uploading soon Masks A mask is a binary pattern used with bitwise operations (such as AND , OR and XOR ) to manipulate specific bits within a binary value . An AND mask is used to clear (set to 0 ) specific bits . Any bit ANDed with 0 becomes 0 , and any bit ANDed with 1 stays the same . For example, 1011 0110 AND 0000 1111 = 0000 0110 - the mask keeps only the lower four bits . An OR mask is used to set (turn on ) specific bits . Any bit ORed with 1 becomes 1 , and with 0 stays the same . For example, 1010 0000 OR 0000 1111 = 1010 1111 . An XOR mask is used to toggle (invert ) specific bits . Any bit XORed with 1 flips (0 → 1 or 1 → 0 ), while XORed with 0 stays the same . For example, 1010 1010 XOR 0000 1111 = 1010 0101 . YouTube video uploading soon Character Sets A character set is a collection of characters (letters , numbers , symbols and control codes ) that a computer can recognise , store and process . Each character is represented by a unique binary code . ASCII (American Standard Code for Information Interchange ) is an early character set that uses 7 bits to represent 128 characters , including English letters , digits , punctuation and control characters . It’s simple and compact but limited to English and basic symbols . Extended ASCII uses 8 bits for 256 characters . Unicode was developed to overcome ASCII’s limitations by representing characters from all languages and writing systems . It uses up to 32 bits and includes over 140,000 characters , allowing consistent representation of text across different devices and platforms . YouTube video uploading soon This page is under active development. Check here for the latest progress update. Q uesto's K ey T erms Data Types: integer, real, Boolean, character, string Number Systems: binary, denary (decimal), hexadecimal, sign and magnitude, two's complement, binary addition, binary subtraction, floating point, floating point normalisation, floating point addition, floating point subtraction Binary shifts: left shift, right shift Masks: mask, bitwise operator, AND, OR, XOR Character Sets: character set, ASCII, Unicode D id Y ou K now? Gottfried Wilhelm Leibniz , a German mathematician , is credited with inventing the binary number system in the 17th century , hundreds of years before computers existed. Leibniz biscuits are named after him. 3.4 - Web Technologies A-Level Topics 4.2 - Data Structures

Learn about the different skills and attributes that are required for IT roles including a network manager, programmer, animator and technician. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 4.5 - Job Roles Exam Board: OCR Specification: 2016 - Unit 1 There are several different IT-related roles within most companies. Each role requires specific skills and attributes to be performed successfully. Try to apply the most suitable personal attributes that were described in 4.3 , as well as any other important skills relevant to the role , such as programming. Self-motivation Leadership Respect Dependability Punctuality Problem Solving Determination Independence Time Management Team Working Numerical Skills Verbal Skills Planning & Organisation Network Manager A network manager must control a group of employees with strong leadership to clearly set out their vision for the team. They must be able to motivate and encourage the team members to meet objectives . Because a network manager is high-ranking, there may not be many senior staff above them so they must be self-motivated and able to complete tasks independently , without being monitored . Network managers must be dependable and decisive , able to weigh up the consequences of a decision and make tough calls whilst under pressure . Time management is an important attribute for a network manager, they must be able to prioritise tasks and ensure deadlines are kept to . IT Technician IT technicians must have good interpersonal skills so that they can communicate clearly with other employees or customers. They should be able to use simplified terminology to help another person with their problem. They must be able to use questioning effectively to work out what the issue is to begin to solve it. IT technicians should have plenty of experience with hardware and software troubleshooting and be able to use a range of troubleshooting tools to solve a problem. They need to be respectful to customers and employees when solving a problem and show determination , as well as self-motivation , to fix issues within acceptable time limits . Programmer A programmer needs to be competent in specific programming languages that the company use. It would be beneficial to have knowledge of more than one programming language so they can be more versatile and approach a problem in different ways . Programmers need to have a logical mind so that they are able to creatively solve problems. Using computational thinking is an important set of skills that programmers should have - for example, by using decomposition to break a large problem into smaller, more manageable chunks. They must have good planning and organisational skills so that they can stay on top of the numerous tasks that need to be done. They need good time management skills to prioritise the more important tasks and stick to a deadline . Programmers must be patient individuals, all programs will contain errors that must be debugged and rewritten numerous times. Good interpersonal skills are necessary so programmers can work efficiently in teams - often multiple programmers will work on subsections of the same program that fit together later. Web Designer & Animator Web designers create , plan and code web pages to fit specific requirements made by their customers. They must create both the technical and graphical aspects of the web page, editing both how it looks and how it works. Web designers could also be responsible for maintaining a site that currently exists. They would need to have sufficient knowledge of using HTML (HyperText Markup Language ) for the structure and content of the webpage and CSS (Cascading Style Sheets ) for the formatting and style . An animator may use a mixture of digital and hand-drawn images or even puppets and models. The main skill of animation is still artistic ability , but there is an ever-increasing need for animators to be experienced with technical computer software . Animators usually work as part of a team with strict deadlines . Q uesto's Q uestions 4.5 - Job Roles: 1. Describe the key skills and personal attributes that a new programmer should have. [10 ] 2. A brief job description of a web designer and an animator are shown above on this page. Use the descriptions of what makes a suitable network manager, IT technician and programmer to help you explain which personal attributes and skills are required for: a) A web designer b) An animator [8 each ] 4.4 - Ready for Work Topic List 4.6 & 4.7 - Bodies & Certification

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:

Learn how to input strings (text) in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 2a - Inputting Text Inputting Text (Strings) in Python A string is a collection of characters (letters, numbers and punctuation) such as: “Wednesday” , “Toy Story 4” or “Boeing 747” . Use the input command to ask a question and let a user input data , which is automatically stored as a string . Variable to save the answer into. Give it a suitable name based on the input. name = input ( "What is your name? " ) = What is your name? Paulina Type your answer directly into the editor and press the Enter key. Statement that is printed to the screen. Leave a space to make the output look clearer. Once an input has been saved into a variable, it can be used for other purposes, such as printing it within a sentence : name = input ( "What is your name? " ) print ( "It is nice to meet you" , name) = What is your name? Jake the Dog It is nice to meet you Jake the Dog Always choose an appropriate variable name when using inputs. colour = input ( "What is your favourite colour? " ) print ( "Your favourite colour is " + colour + "? Mine is yellow." ) = What is your favourite colour? blue Your favourite colour is blue? Mine is yellow. Inputting Text Task 1 ( Holiday) Write an input line to ask the user where they last went on holiday . Write a print line that uses the holiday variable (their answer). Example solution: Where did you last go on holiday? Scotland I hope you had a nice time in Scotland Inputting Text Task 2 ( New Neighbour) Write an input line to ask the user for a title (e.g. Mr, Mrs, Dr). Write another input line for an object . Write a print line that uses both input variables (title and object ). Example solutions: Enter a title: Dr Enter an object: Fridge I think my new neighbour is Dr Fridge Enter a title: Mrs Enter an object: Armchair I think my new neighbour is Mrs Armchair Using a Variable Within an Input To use a variable you have previously assigned a value t o within the input statement you must use + (commas will not work). drink = input ( "What would you like to drink? " ) option = input ( "What would you like with your " + drink + "? " ) print ( "Getting your" , drink , "and" , option , "now...." ) = What would you like to drink? tea What would you like with your tea? biscuits Getting your tea and biscuits now... What would you like to drink? apple juice What would you like with your apple juice? cake Getting your apple juice and cake now... Inputting Text Task 3 ( Name & Game) Ask the user what their name is. Ask the user what their favourite game is. Use their name in the input statement for their game. Print a response with their name and the game they entered. Example solutions: What is your name? Rory Hi Rory, what's your favourite game? Minecraft Rory likes Minecraft? That's nice to know. What is your name? Kayleigh Hi Kayleigh, what's your favourite game? Stardew Valley Kayleigh likes Stardew Valley? That's nice to know. ⬅ Section 1 Practice Ta sks 2b - I nputting Numbers ➡

Learn how to embed images into your HTML web page using the img tag. Learn how to resize an image to your desired width and height. 5. Images HTML Guide Watch on YouTube: Images can be added to your web page to make it more visual. The guide below shows you how to find a picture online, download it and place it in your web page. Find & Save the Image Firstly you can perform a Google Image search to find a picture that you like. As an ethical Computer Scientist, you should be searching for copyright free images. Click on Tools and then Usage Rights to change it to 'Labeled for reuse'. Choose an appropriate image and download it to the same folder as your html file. Save the image in the same folder as where your HTML file is saved . If you don't do this, your image won't work . If you are using a school computer and the image automatically downloads , without giving you the option to rename it and save it, click on 'Show in folder' and move it to the folder where your HTML file is . Make sure that the image is saved in the exact same folder as your HTML file and that is has a suitable name . Create the Image Tag The tag for images does not have an end tag - it is all written within one set of angle brackets. src stands for source . You must type the image exactly as it is saved , including the file type (e.g. .jpg or .png). Don't forget the speech marks either. Create the img tag, using the exact name of the image you downloaded. Change the Image Size You can directly state the width and height of the image by defining the style within the image tag. If your image is too large or too small, change the size of it yourself. Next it is time to organise the web page further so it looks more like a professional site. 4. Hyperlinks HTML Guide 6. Organisation

Learn about the different protocols used to transfer data across a network, including TCP/IP, FTP, SMTP and Ethernet. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 2.7 - Protocols Exam Board: OCR Specification: 2016 - Unit 1 What is a protocol? A protocol is a set of rules that allow devices on a network to communicate with each other . Protocols to Transfer Data: TCP / IP / UDP TCP ( Transmission Control Protocol ) breaks data down into small packets to be transferred across a network and reorders them back into the original data at the destination . TCP checks for errors when sending data packets, which makes it slower than UDP for data transfer, but it guarantees that no packets have been lost on the way. IP ( Internet Protocol ) is in charge of routing and addressing data packets to ensure data is transferred across networks to the correct destination . It is also an addressing system - every device on a network is given a unique IP address . TCP and IP are often used together to transfer data across the internet. UDP ( User Data Protocol ) is a faster alternative to TCP for transferring data. It is used where low latency ('low lag') is important, such as online gaming and video chat . However, UDP does not automatically check for errors so packets are more likely to be lost or received out of order . HTTP is a protocol that can be used to transfer web pages on the world wide web 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 (Hyper Text Transfer Protocol) FTP (File Transfer Protocol) FTP ( File Transfer Protocol ) is used to transfer files across a network. It is used most often to upload or download files to/from a file server . ICMP ( Internet Control Message Protocol ) collects network status information (such as router errors) and is used for troubleshooting . SNMP ( Simple Network Management Protocol ) is a protocol that records network statistics , such as router usage . Network Management Protocols Email Protocols SMTP ( Simple Mail Transfer Protocol ) is a protocol used to send emails to a mail server and between mail servers . POP ( Post Office Protocol ) is for downloading and storing emails from a mail server. TCP/IP Protocol Stack The TCP/IP protocol stack is a model split into 4 layers . The model is used to visualise the different parts of a network as each of the four layers has a specific role . Splitting a network design into layers is beneficial to programmers as it simplifies design , making it easier to modify and use . Each layer has a certain purpose and is associated with different protocols . 4 Allows humans and software applications to use the network e.g. browsers (HTTP /HTTPS ), email (SMTP / POP ), file transfer (FTP ) and network management (SNMP ) applications. 3 TCP breaks the data down into data packets . This layer makes sure the data is sent and received in the correct order and reordered at the destination without errors. UDP can also be used for faster , but less reliable , data transfer . 2 The network layer is also known as the ' Internet Layer '. IP is responsible for addressing and routing data packets . The optimal route for the data to take is calculated in this layer. ICMP may be used here for network monitoring . 1 This layer handles transmission errors and passes data to the physical hardware such as routers . It also sets out the final format of data packets . Q uesto's Q uestions 2.7 - Protocols: 1. Describe each of the following protocols . Also, state the protocol's full name and draw an icon or diagram for each: a. TCP b. IP c. UDP d. HTTP & HTTPS e. FTP f. ICMP g. SNMP h. SMTP i. POP [1 each ] 2. State which protocol would be used in the following scenarios: a. Transferring a music file to a friend over the internet. b. Sending an email to a friend in Japan. c. Checking for errors on a network. d. Having a video call with a colleague in London. e. Receiving an email from the bank. f. Watching a video on YouTube. g. Checking the statistics of usage on a network [1 each ] 3. Summarise each layer of the TCP/IP stack and identify the protocols used in each layer . [ 8 ] 2.6 - Software Troubleshooting Topic List 3.1 - Server Types

Learn about the six programming errors - syntax, runtime (execution), linking, logical, rounding and truncation. Based on the 2020 Eduqas (WJEC) GCSE specification. 10.3: Programming Errors Exam Board: Eduqas / WJEC Specification: 2020 + Syntax Error A syntax error is a mistake in the grammar or spelling of the program. A syntax error will prevent the program from being compiled . Examples: Incorrect Spelling: pront ( "hello" ) Incorrect punctuation: print ( "hello" ( Execution (Runtime) Error An execution error is when the program unexpectedly stops as a result of an operation during execution . Examples: Dividing by zero: 400 / 0 Reading too far in a file: #There are 50 lines in the file line = file.readlines( ) print ( line [100] ) Logical Error Linking Error A logical error is a mistake made by the programmer - the program still works but displays the wrong output . Examples: Truncation Error Rounding Error A linking error occurs when a compiler can’t find a sub procedure (e.g. the random library in Python) that has been used. The programmer might have declared it incorrectly or forgotten to link (import) it . Examples: Spelling an import command incorrectly: import ramdon number = random.randint(1,10) Requesting a function without linking: number = random.randint(1,10) Incorrect calculation: total = num1 - num2 print (total) Incorrect variable printed: age = 16 name = "Steve" print ( "Nice to meet you" , age) A rounding error is when the program rounds a real number to a fixed number of decimal places. This results in losing some value as the number becomes less accurate . Examples: Rounding up: 80.87 = 80.9 (Inaccurate by 0.03) Rounding down: 63.4 = 63 (Inaccurate by 0.4) A truncation error is when the program truncates a real number to a fixed number of decimal places . This results in losing some value as the number becomes less accurate . Examples: Truncation to 2 decimal places: 92.13787 = 92.13 (Inaccurate by 0.00787) Truncation to 1 decimal place: 25.199876 = 25.1 (Inaccurate by 0.099876) Q uesto's Q uestions 10.3 - Programming Errors: 1. Describe and give an example of each type of error: a. Syntax Error [ 3 ] b. Execution (Runtime) Error [ 3 ] c. Logical Error [ 3 ] d. Linking Error [ 3 ] e. Rounding Error [ 3 ] f. Truncation Error [ 3 ] 2. State the error that will occur for each scenario: [1 each ] a. A command word (such as for or print) has been misspelt. b. The average speed is 120.3856 but only 120.3 is displayed. c. The cost of a meal is £47 but £40 is displayed. d. A program uses a subroutine that has not been imported. e. The height of a dog is 33.38cm but 33.4cm is displayed. f. The user wants to read line 9 of a file that only has 6 lines. g. The user's age is printed instead of their name. h. The programmer has typed print("hello"( i. A number is divided by 0. j. The program is asked to generate a random number but 'import random' has not be written. 10.2 - Stages of Compilation Theory Topics 11.1 - Impacts of Technology

Learn about the motherboard and the components that are connected to this important piece of computer hardware. The Motherboard What is a motherboard? The motherboard is the main circuit board of a computer that links all other components together. Components can communicate by sending signals and data across pathways called buses . Some components, like the CPU and RAM , are directly installed in special sockets on the motherboard . There are expansion slots for further components like a graphics card . What is connected to the motherboard? Central Processing Unit Random Access Memory Graphics Processing Unit Read Only Memory Cache Memory Sound Card Hard Disk Drive Power Supply Unit What is a motherboard's form factor? Form factor relates to the motherboard's size , shape and how many components it can fit . The three most common form factors are compared below: ATX Micro ATX Mini ITX Standard Small Very Small 32 GB 64 GB 128 GB 7 4 1 Size Max RAM Expansion Card Slots GB stands for gigabytes What ports does a motherboard have? The motherboard contains several ports on the back panel , allowing cables to be connected to input or output data . Below are some of the common ports : USB (Type-A) Connects input devices like keyboards and mice or storage devices like a USB memory stick. USB (Type-C) A newer type of USB that is faster and commonly used to charge devices or transfer data. Ethernet Allows a device to connect to a wired network, most commonly to a router, for internet access. HDMI Connects to a monitor or TV to show the computer's audio and visual output. KS3 Home

Learn about different types of operating systems and the various roles that they manage, including memory, security and processing. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 2.4: Operating Systems Exam Board: OCR Specification: 2016 - Unit 1 An operating system (OS) is software that manages the resources of a computer system . The operating system is loaded by the BIOS (Basic Input / Output System). Types of Operating System Single user operating systems are found on most desktop computers, laptops and tablets where only one person will use the device at a single time. Multi-user operating systems allow more than one user to access the processor simultaneously , such as a server that users, with correct permissions , can access remotely . However, one user should not be negatively impacted by another user on the same operating system and security must be managed carefully as data may be visible to other users . Single Processor operating systems have only a single processor (CPU), which is shared between users by dividing the CPU time into time-slices and allocating one of these to each user in turn. The time-slices are very short, giving each user the impression that their programs are running continuously. Multiple Processor operating systems have more than one processor (CPU). Users still have to share processors and it is a more complicated system but performance is improved as there are fewer users per processor. Some supercomputers have thousands of processors running in parallel. Operating systems can also be off-the-shelf , open-source or bespoke . See 2.1 . What are the roles of an Operating System? Manage Input / Output Devices Receives data from input devices (e.g. a keyboard). Sends data to output devices (e.g. a monitor) in the correct format . Manage Printing Checks the printer is free then uses spooling (storing data in a queue ) to print documents in order. Manage Backing (Secondary) Storage Ensures data is stored correctly and can be retrieved from secondary storage devices (e.g. hard drive / SSD ). Organises files in a hierarchical structure. Manage Memory (RAM) Ensures that programs / data do not corrupt each other and are stored in correct memory locations . Manage Processes Ensures different processes can utilise the CPU and do not interfere with each other or crash. On most OS the tasks appear to run simultaneously . Manage Security Allows users to create, manage and delete user accounts with different permissions. Allows users to logon and change passwords . User Interface The final function of an operating system is to provide a user interface . This includes: A folder and file system is displayed and manipulated allowing for copying , searching , sorting and deleting data. Icons are displayed to represent shortcuts to applications and files. Multiple windows can be opened at the same time and switched between. The interface can be customised , such as changing font sizes and the desktop background . System settings can be accessed such as network and hardware options . Q uesto's Q uestions 2.4 - Operating Systems: 1. Describe five different roles of the operating system. Include the importance of the operating system in performing each role. [ 5 ] 2. What is the difference between single user and multi-user operating systems? [2 ] 3. What is the difference between single processing and multi-processing operating systems? [2 ] 4. Using your knowledge from 2.1 Software Types, explain two advantages and one disadvantage to a company if they decided to use a closed source operating system. [6 ] 2.3 Utility Software Topic List 2.5 Communication Methods

Learn how to handle errors in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. Python 12 - Error Handling Errors When an error occurs in Python, you may see a chunk of red text like this. This is very useful when creating programs as it tells us the exact line of the error (10), and its type (NameError). However, a completed program should have code in place for when an unexpected error occurs – we call this exception handling . General Exception In this example, Python will attempt to run the code indented beneath try . If there are no errors then the code will stop just before except . If an error does occur then the Exception code will be run . If we enter a correct value then the program will execute normally: But if an error occurs (such as writing a string when an integer is expected) then the Exception code will run : You can add the else command to your code that will execute only if there are no errors : If a valid number is entered then the else code will be printed: If a code generating an error is entered then the except code will be printed: Practice Task 1 Create a program that asks the user to input their age. Don't forget to use the int command. Use try and except to print a message if a number is not inputted. Example solution: Specific Exceptions The Exception command used in the section above is for any general error that occurs. You can also use specific except commands for a variety of errors. Below is a program with two different specific exception commands for one try statement: If a Value Error occurs, such as when the wrong data type is entered , then related code will be printed: Or if the user tries to divide by zero then a Zero Division Error will be triggered which prints a relevant response: Other types of exception can be found here . Practice Task 2 Create a program that asks the user to input a number and then divides this value by 999. Create a Value Error and Zero Division Error exception and include an appropriate message in both. Example solution for Zero Division: ⬅ 11 - Graphical User Interfac e Extended Task 1 (Pork Pies) ➡