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4.8: Compression Exam Board: Eduqas / WJEC Specification: 2020 + What is compression? To compress a file means to make its size smaller . Benefits of compression include: ​ Files take up less storage space (so more files can be stored). Files can be transferred quicker (because they are smaller). Files can be read from or written to quicker . ​ There are two methods that are used to compress files: Lossy and Lossless . Lossy Compression Lossy compression uses an algorithm (set of instructions) to analyse a file and remove data that cannot be heard or seen by humans . For example, a lossy algorithm would analyse the sound waves of an audio file and remove any frequencies which humans cannot hear. This process reduces the size of the file . ​ Further lossy compression will remove data that humans can see / hear . For example, the dog image to the right has been strongly compressed using a lossy algorithm and some data has clearly been removed. Lossy compression removes the data permanently , so the file can never return to its original form . ​ Lossy compression is often used with images , audio and video to reduce the file size, for example to send over the internet. Lossless Compression Lossless compression reduces the size of a file without permanently removing any data . Because of this, the file is returned to its original form when decompressed, so no quality is lost . ​ A file that is compressed with a lossless algorithm is usually larger than a file compressed with a lossy algorithm because no data has been permanently removed. Lossless compression is used with files that would not work if data was removed, for example executable files (e.g. programs and games) or word documents . Remember that lossy and lossless compression do not just refer to images. Below is an audio file that has been compressed with lossy compression . Data has been removed so the audio quality has decreased. 197 KB 81 KB 43 KB Compression Ratios Original File Size Compression Ratio = Compressed File Size 4 Mb = 5:1 20 Mb Example: A file has been compressed from 20 megabytes down to 4 megabytes. This is a compression ratio of 5:1. To calculate the size after compression , divide the original size by the first ratio value, then multiply it by the second value. For example, the new size for file 1 is (210 ÷ 10) x 3 = 63 MB. Triple-click the final column to see the right answers. Q uesto's Q uestions 4.8 - Compression: 1. Describe 3 benefits of compressing a file . [ 3 ] 2. Describe the differences between lossy and lossless compression . [4 ] ​ 3. A student needs to compress a Microsoft Word document to send in an email. Suggest which type of compression they should use and why . [ 2 ] ​ 4a. A text file was 72 KB and was compressed to 8 KB . State the compression ratio . 4b. An audio file was 4.5 MB and has been compressed to 0.9 MB. State the ratio. 4c. A 20 MB file is compressed with a ratio of 5:2 . What is the size of the compressed file ? [ 1 each ] 63MB 164KB 96KB 4.7 Sound Representation Theory Topics 5.1 - Data Structures

5.3 - Threats Exam Board: OCR Specification: 2016 - Unit 1 What are the 7 threats to computer systems? Phishing Misleading individuals or organisations into giving up sensitive information (such as passwords or bank details), often through the use of emails . Hacking Exploiting weaknesses in a system or network to create, view, modify or delete files without permission. Similar to data theft - illegally removing copies of personal or company data from computer systems. :( Trojan Appears to be a useful or well-known program but when downloaded and installed it secretly gives the attacker a ' backdoor ' to your system. Through this backdoor the attacker can access data without the user knowing. Football 2020 FREE Interception Data packets on a network are intercepted by a third party (e.g. hacker) and copied, edited or transferred to a different location than the intended destination. Eavesdropping Intercepting , in real-time , private communication traffic such as instant messages or video calls . Social Engineering Tricking individuals into giving sensitive information , e.g. by claiming to be from the IT department and asking for their password and username to check for viruses. Virus A virus can replicate itself and spread from system to system by attaching itself to infected files that are then downloaded and opened. Once activated, a virus can modify data or corrupt a system so that it stops working. Q uesto's Q uestions 5.3 - Threats: ​ 1. An IT company is making an information booklet about the different types of online threats . Describe each type of threat: a. Phishing b. Hacking / Data Theft c. Trojan d. Interception e. Eavesdropping f. Social Engineering g. Virus [2 each ] 5.2 - Operational Issues Topic List 5.4 - Physical Security

2.2: Data Types Exam Board: OCR Specification: J277 What are the different data types? When programming, variables should be given appropriate data types . Character A single character , such as a letter, number or punctuation symbol. ​ Examples: T 8 ? String A sequence of characters , including letters, numbers and punctuation. ​ Examples: Harry Waters 14:50pm Ice Age 4 Integer A whole number . ​ ​ ​ Examples: 475 -8432 56732 Real Boolean A decimal number . ​ ​ Examples: 65.3 -321.1234 909.135 An answer that only has two possible values . ​ Examples: True / False Yes / No 0 / 1 Telephone numbers are always stored as a string , not an integer. Casting Converting the value of a variable from one data type into another is known as casting . ​ Python automatically assumes an input is a string so the int() command is used to cast an input into an integer . Other Python commands for casting include str() and float() . ​ For example: age = int(input("Enter your age: ")) Q uesto's Q uestions 2.2 - Data Types: ​ 1. List the five data types , giving an example of each . [ 5 ] ​ 2. 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 ] ​ ​ 3. Explain what casting is and give a programming situation in which it would be used . [ 2 ] 2.1 - Programming Fundamentals Theory Topics 2.3 - Additional Techniques

OCR Computer Science A-Level Component 1: Computer Systems These pages are based on content from the OCR Computer Science 2015 specification . This website is in no way affiliated with OCR . 1. Hardware 1.1a - The CPU & FDE Cycle 1.1b - Performance 1.2 - Processors 1.3a - Input & Output Devices 1.3b - Memory & Storage 2. Software 2.1 - Operating Systems 2.2a - Applications & Utilities 2.2b - Translators & Compilation 2.3 - Software Development Methodologies 2.4a - Programming & Pseudocode 2.4b - Assembly Language 2.4c - Object-Oriented Language 3. Networks & Databases 3.1a - Compression 3.1b - Encryption & Hashing 3.2a - Databases & Normalisation 3.2b - SQL 3.3a - Network Characteristics 3.3b- Protocols & TCP-IP Stack 3.3c - Network Hardware & DNS 3.3d - Network Security & Threats 3.4a - Web Technologies 3.4b - HTML, CSS & JavaScript 4. Data & Logic 4.1a - Data Types & Character Sets 4.1b - Denary, Binary & Hexadecimal 4.1c - Signed Binary & Floating Point 4.1d - Binary Calculations 4.1e - Shifts & Masks 4.2 - Data Structures 4.3a - Logical Operators & Truth Tables 4.3b - Flip Flops, Adders, Laws & Maps 5. Laws 5.1 - Computer Legislation 5.2 - Moral & Ethical Issues

5. Play Sounds 1. Check the Sounds Folder Greenfoot Tutorial Sound files must be placed the ' sounds ' folder of your Greenfoot project to be used in the game. ​ In the Component 2 exam of the WJEC / Eduqas 2016 specification , an audio file will be placed in the sounds folder already . ​ For this example game you can download the audio clips to the right and paste them into your sounds folder . Watch on YouTube: Click the audio icon to download a zip folder of the two sound files below . Copy the files into the sounds folder of your Greenfoot project . < Part 4 - Remove Objects 2. Add the playSound Method Add the code to play the sound at the same time as when the collectible object is removed . ​ The name of the file and its extension (e.g. .wav or .mp3 ) must be written in speech marks after the playSound method. Part 6 - The Counter >

Algorithms Pseudocode Pseudocode Pseudocode is not a specific programming language but a more general method of describing instructions . It should be unambiguous, and it should not resemble any particular kind of programming language (e.g. Python or Java), so it can theoretically be turned into real code in any language. ​ Generally, pseudocode can be written in any way that is readable and clearly shows its purpose. However, the Eduqas exam board advises that pseudocode for the programming exam should follow the conventions below : Annotation { Write your comment in curly brackets} ​ Define data type price is integer firstname is string ​ Declare a variable's value set price = 100 set firstname = "Marcella" ​ Input / output output "Please enter your first name" input firstname Selection (must have indentation) if firstname = "Steven" then​ output "Hello" + firstname elif firstname = "Steve" then output "Please use full name" else output "Who are you?" end if ​ Iteration (while loop) while firstname ! = "Steven" output "Guess my name." input firstname repeat Iteration (for loop) for i in range 10 input item next i ​ Define a subroutine Declare Sub1 [Subroutine content indented] End Sub1 ​ Call a subroutine call Sub1 Flowcharts flowchart A flowchart can be used to visually represent an algorithm. The flowchart symbols are: Algorithm Example example Pseudocode {This is a program to see how many items you can buy in a supermarket before you spend over £100} ​ total is integer, itemsentered is integer, itemprice is integer set total = 0 set itemsentered = 0 ​ while total < 100 output "enter the price of the next item" input itemprice total = total + itemprice itemsentered = itemsentered + 1 repeat if itemsentered >= 20 then output "You are on your way to saving money." elif itemsentered => 30 then output "You're a real money saver." else output "Look for better deals next time." end if Stop Flowchart

2.2: Applications Software Exam Board: OCR Specification: 2016 - Unit 1 What is applications software? Don't confuse applications software and apps . Apps generally have a single use, such as Angry Birds or the flashlight tool on a phone. ​ Applications Software can be used for a number of different functions depending on the user's needs and their purpose. Productivity Software This is general use software for completing tasks accurately and efficiently . Key examples include word processors (e.g. Microsoft Word or Google Docs), presentation software (e.g. Microsoft PowerPoint or Google Slides) and web browsers (e.g. Microsoft Edge or Google Chrome). ​ Email applications (e.g. Microsoft Outlook or Gmail) are beneficial to organisations because staff can send information to many customers at once which is a simpler and less costly method of communication than something like sending letters or leaflets in the mail. Emails can also include attachments of important documents and include multimedia elements like images and videos to make communication more interesting . Databases and Spreadsheets ​ Database tables and spreadsheets can store both numerical and textual data ready for analysis. Examples include simple database tables and financial spreadsheets of a company's profits this year. Microsoft Access is an example of database software that uses tables and Microsoft Excel is an example of spreadsheet software. Data can be sorted numerically or alphabetically for both software types but graphs can be created from spreadsheets to visualise data . ​ When using spreadsheets (or databases) records can be locked ('record locking' ) so that only one person can make edits at any one time. Edits will be saved before unlocking the file. This will stop data being incorrectly overwritten and will ensure that the data in the spreadsheet is up-to-date, accurate and fit for purpose. ​ An advantage of databases over spreadsheets is that data can be atomised - stored in separate tables but linked through relationships. Development Tools These are tools for programmers who are creating or modifying software . An integrated development environment ( IDE ) is software used to create and edit programs. An IDE features a number of tools including: ​ A translator is a program that converts one type of language into another. A compiler is a type of translator that converts instructions into machine code (binary). A debugger is used to test code and display errors . ​ Other development tools aid programmers with developing and maintaining websites and apps for phones / tablets. Wix.com has been used to create and update this website. Business Software This is specialist software for businesses , often made bespoke for an organisation. One example of business software is design packages such as CAD / CAM (C omputer-A ided D esign / C omputer-A ided M anufacturing). This is the use of software to design and construct products . Workers such as manufacturers and dentists use this type of software. ​ Another type of business software is project management software that allows teams of workers to collaborate and divide projects into manageable tasks. Expert systems use large databases for automatic decision making , such as medical diagnosis programs . Further examples of business software, such as Management Information Systems (MIS), can be found in 3.5 . Q uesto's Q uestions 2.2 - Applications Software: ​ 1. State four different kinds of productivity software and briefly describe how each could be used . For example: "Word processors can be used to type up a letter in an office or write an essay for school." [8 ] ​ 2. Describe two differences between database and spreadsheet software. [2 ] ​ 3a. What is an Integrated Development Environment ? [1 ] 3b. Describe three tools used in an IDE. [6 ] 4. Giving brief examples of how they can be used, state four different types of business software . [8 ] 5. Suggest how a website design company could use each of the three types of applications software (Productivity Software , Development Tools and Business Software ). [ 6 ] 2.1 - Types of Software Topic List 2.3 - Utility Software

2.1: Logical Operators & Truth Tables Exam Board: Eduqas / WJEC Specification: 2020 + What is a logical operator? Inside of each computer system are millions of transistors . These are tiny switches that can either be turned on (represented in binary by the number 1 ) or turned off (represented by 0 ). ​ Logical operators are symbols used to represent circuits of transistors within a computer. The four most common operators are: ​ NOT AND OR XOR What is a truth table? A truth table is a visual way of displaying all possible outcomes of a logical operator. The input and output values in a truth table must be a Boolean value - usually 0 or 1 but occasionally True or False. NOT A NOT logical operator will produce an output which is the opposite of the input . ​ NOT is represented by a horizontal line . Boolean Algebra Notation written as NOT A A Truth Table AND An AND logical operator will output 1 only if both inputs are also 1 . ​ AND is represented by a full stop. Boolean Algebra Notation written as A AND B A.B Truth Table OR An OR logical operator will output 1 if either input is 1 . ​ OR is represented by a plus. Boolean Algebra Notation written as A OR B A+B Truth Table XOR An XOR (exclusive OR) logical operator will output 1 if the inputs are different and output 0 if the inputs are the same . ​ XOR is represented by a circled plus. Boolean Algebra Notation written as A XOR B A B Truth Table Multiple Operations Exam questions will ask you complete truth tables that use more than one logical operator . Work out each column in turn from left to right and look carefully at which column you need to use. Simplification You may be asked to use a truth table to simplify an expression . ​ This is actually really easy. Once you've completed the truth table see if any columns match the final expression . A+B and A+(A+B) both result in the same values , therefore: A+(A+B) can be simplified as just A+B. Q uesto's Q uestions 2.1 - Logical Operators: ​ 1. Copy and complete the following truth tables: ​ ​ ​ 1b. Simplify the expression in the second truth table. ​ 2a. A cinema uses a computer system to monitor how many seats have been allocated for upcoming movies. If both the premium seats and the standard seats are sold out then the system will display a message. State the type of logical operator in this example. 2b. For the more popular movies, the cinema's computer system will also display a message if either the premium seats or the standard seats have exclusively been sold out. However, it will not output a message when both have been sold out. State the type of logical operator in this example. 1.6 - Additional Hardware 2.2 - Boolean Algebra Theory Topics

4.1: Number Systems Exam Board: Eduqas / WJEC Specification: 2020 + What is binary? By now you should know that computer systems process data and communicate entirely in binary . ​ Topic 1.4 explained different binary storage units such as bits (a single 0 or 1), nibbles (4 bits) and bytes (8 bits). ​ Binary is a base 2 number system. This means that it only has 2 possible values - 0 or 1 . ​ Because binary is a base 2 number system, binary numbers should be written out with a 2 after them, like this: 10101002 What is denary? Denary (also known as decimal ) is the number system that you've been using since primary school. ​ Denary is a base 10 number system. This means that it has 10 possible values - 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 . ​ Because denary is a base 10 number system, denary numbers should be written out with a 10 after them, like this: 165 10 How to convert from binary to denary: How to convert from denary to binary: What is hexadecimal? Hexadecimal is a base 16 number system. This means that it has 16 possible values - 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F . ​ Because hexadecimal is a base 16 number system, hexadecimal numbers should be written out with a 16 after them, like this: 6E16 ​ Hexadecimal is used as a shorthand for binary because it uses fewer characters to write the same value . This makes hexadecimal less prone to errors when reading or writing it , compared to binary. For example, 1001111010112 is 9EB16 . ​ Hexadecimal only uses single-character values. Double-digit numbers are converted into letters - use the table on the right to help you understand. How to convert from binary to hexadecimal: How to convert from hexadecimal to binary: Converting from denary to hexadecimal / hexadecimal to denary To convert from denary to hexadecimal or the other way round you must convert to binary first . ​ Denary > Binary > Hexadecimal ​ Hexadecimal > Binary > Denary ​ Use the videos on this page if you need help converting to or from binary. ​ The most common number systems question in exams are from denary to hexadecimal or from hexadecimal to denary so make sure that you practice these conversions. Q uesto's Q uestions 4.1 - Number Systems: ​ 1. Explain why hexadecimal numbers are used as an alternative to binary . Use an example . [ 3 ] ​ 2. Convert the following values from binary to denary : a. 00101010 2 b. 11011011 2 c. 01011101 2 d. 11101110 2 e. 01011111 2 [1 each ] ​ 3. Convert the following values from denary to binary : a. 35 10 b. 79 10 c. 101 10 d. 203 10 e. 250 10 [1 each ] ​ 4. Convert the following values from binary to hexadecimal : a. 11110101 2 b. 01100111 2 c. 10111010 2 d. 10010000 2 e. 11101001 2 [1 each ] ​ 5. Convert the following values from hexadecimal to binary : a. C2 16 b. 8A 16 c. DE 16 d. 54 16 e. F7 16 [1 each ] ​ 6. Convert the following values from denary to hexadecimal : a. 134 10 b. 201 10 c. 57 10 d. 224 10 e. 101 10 [1 each ] ​ 7. Convert the following values from hexadecimal to denary : a. 32 16 b. A5 16 c. 88 16 d. C0 16 e. BE 16 [1 each ] Watch on YouTube Watch on YouTube Watch on YouTube Watch on YouTube Click the banners above to try self-marking quizzes (Google Form) on these topics. Denary to Binary: Binary to Denary: Binary to Hexadecimal: Hexadecimal to Binary: 3.9 Protection Against Threats Theory Topics 4.2 - Signed Binary

4.6 & 4.7 - Bodies & Certification Exam Board: OCR Specification: 2016 - Unit 1 What is a professional body? A professional body is an organisation that seeks to develop and support workers in a certain profession. ​ Professional bodies will share best practice , help people starting in the profession and support any role-related learning . ​ In the UK a popular professional body is the British Computer Society (BCS) - also known as the Chartered Institute for IT - with over 65,000 members. What is industry certification? Professional bodies exist to provide trainees with industry certification . Industry certifications are qualifications in different areas of expertise so applicants are trained with up-to-date knowledge and skills . ​ Two popular organisations that administer industry certifications in America are Cisco and CompTia . Cisco's website claims that they provide "certifications for all experience levels covering topics in networking , security , collaboration , and more. Cisco's certification program can meet you where you are on your learning journey and take you to where you want to go." Advantages of Industry Certification Disadvantages of Industry Certification Develop IT skills: ​ Trainees develop experience and competency in areas relevant to actual jobs. Access resources: Trainees are part of a network of like-minded professionals with access to help from experts . P rofessional development opportunities: ​ Trainees are invited to special events and seminars to ensure skills remain up-to-date . Cost: ​ Training for industry certification can cost hundreds or even thousands of pounds and is often self-funded . No guarantees: ​ Earning a certificate doesn't guarantee you a better job or more money. Time and dedication: ​​ Like other qualifications, classroom activities or online learning must be completed. Exams must be passed at the end of the course. Many organisations now require IT employees to have earned relevant industry certifications​ . This is so that the organisation can be confident that the employee has been appropriately trained and will have gained experience at the required level for the certification. The employee should be able to demonstrate technical knowledge as a result of gaining the certification. Q uesto's Q uestions 4.6 & 4.7 - Bodies & Certification: ​ 1a. What is a professional body ? [1 ] 1b. State 3 roles of a professional body . [3 ] ​ 2. What are industry certifications ? [2 ] ​ 3. Describe 3 advantages and 3 disadvantages of an IT worker earning industry certifications . [2 each ] ​ 4. Why do many IT organisations require its employees to have earned industry certifications ? [4 ] 4.5 - Job Roles Topic List 5.1 - Ethical Issues

Exam Board: OCR 5.2 - Moral & Ethical Issues 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 5.2 - Moral & Ethical Issues: ​ 1. What is cache memory ? [ 2 ] ​ 5.1 - Computer Legislation Theory Topics

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