Switching to AQA from Edexcel

Transcription

1 Switching to AQA from Edexcel This resource compares our new GCSE Computer Science specification (8520) with the new Edexcel Computer Science specification (1CP1). If you are thinking of switching from Edexcel to AQA, you will find this a useful guide to the differences in subject content and assessment. Content The tables below show the topics that are common across our GCSE Computer Science specification (8520) and the new Edexcel Computer Science specification (1CP1) Representing Algorithms Understand and explain the term algorithm. Understand and explain the term decomposition. Understand and explain the term abstraction. Use a systematic approach to problem solving and algorithm creation representing those algorithms using pseudo-code and flowcharts. Explain simple algorithms in terms of their inputs, processing and outputs. Similar expectations to AQA although only 'understand' not 'explain'. Edexcel require students to be able to decompose a problem but do not use the terms 'understand' or 'explain'. Similar expectations to AQA, no reference to explaining the term but does expect students to be able to program abstractions of real-world examples. Similar expectations to AQA, explicitly lists programming constructs. Edexcel refer to determining the correct output for a given set of data. Edexcel also refer to the IPO model under machines and computational modelling (4.1.1)

2 Determine the purpose of simple algorithms. Edexcel also refer to the use of a trace table during development (2.1.6) Efficiency of algorithms Understand that more than one algorithm can be used to solve the same problem. Edexcel refer to the influence of data structures and data values Searching algorithms Understand and explain linear search. Understand and explain binary search. Edexcel refer more generically to understanding how the algorithms work. Compare and contrast linear and binary search algorithms Sorting algorithms Understand and explain merge sort. Understand and explain bubble sort. Edexcel refer more generically to understanding how the algorithms work. Compare and contrast merge and bubble sort algorithms Data Types Understand the concept of a data type.

3 Understand and use the following appropriately: Integer Real Boolean character string Programming Concepts Use, understand and know how the following statement types can be combined in programs: variable declaration constant declaration assignment iteration selection subroutine (procedure/function). Use definite and indefinite iteration, including indefinite iteration with the conditions(s) at the start or the end of the iterative structure. Use nested selection and nested iteration structures. Use meaningful identifier names and know why it is important to use them. No specific reference to different types of iteration. No reference to nesting. Edexcel goes in to more detail regarding producing programs that are easy to read and techniques to aid this.

4 3.2.3 Arithmetic operations in a programming language Be able to use addition, subtraction, multiplication, real division, integer division including remainders Relational operations in a programming language Be able to use equality, inequality, less than and greater than, less than or equal to, greater than or equal to Boolean operations in a programming language Be familiar with and be able to use: NOT AND OR Data structures Understand the concept of data structures. Use arrays (or equivalent) in the design of solutions to simple problems both oneand two-dimensional. Use records (or equivalent) in the design of solutions to simple problems.

5 3.2.7 Input/Output and file handling Be able to obtain user input from the keyboard. Be able to output data and information from a program to the computer display. Be able to read/write from/to a text file String handling operations in a programming language Understand and be able to use: Length Position Substring Concatenation Convert character to character code Convert character code to character String conversion operations. Edexcel expect a student to know how to manipulate strings, but do not give guidance on what string manipulation methods need to be used Subroutines (Procedures and Functions) Understanding the concept of subroutines. Explain the advantages of using subroutines in programs. Similar expectations to AQA

6 Describe the use of parameters to pass data within programs. Use subroutines that return values to the calling routine. Similar expectations to AQA Similar expectations to AQA Know that subroutines may declare their own variables, called local variables, and that local variables usually: Similar expectations to AQA - AQA has more detail on what a local variable is. Only exists while the subroutine is executing. Are only accessible within the subroutine. Use local variables and explain why it is good practice to do so. Edexcel also explicitly covers global variables Robust and secure programming Be able to write simple data validation routines. Be able to select suitable test data (normal, boundary, erroneous) and justify the choice. Edexcel make some reference to selecting test data in algorithms (1.1.9) and adds the requirement of using test plans while having similar expectations to AQA (2.1.4) Classification of programming languages Know about and be able to explain differences between low-level and high-level languages.

7 Understand advantages and disadvantages of low-level and high-level languages. Understand that there are three common types of program translator (interpreter, compiler, assembler), what the main differences are and when it would be appropriate to use each type. Edexcel request students are able to understand the suitability of a high-level or low-level language for a suitable task. Similar expectations to AQA although Edexcel look at advantages and disadvantages rather than appropriateness of usage Number bases Understand decimal, binary and hexadecimal. Understand that computers use binary to represent all data and instructions. Explain why hexadecimal is often used in computer science. Edexcel have expectations of understanding unsigned and signed binary integers Converting between number bases Understand how binary can be used to represent whole numbers. Understand how hexadecimal can be used to represent whole numbers. Be able to convert in both directions between binary, hexadecimal and decimal. Edexcel have expectations of understanding unsigned and signed binary integers. Similar expectations to AQA

8 3.3.3 Units of information Know what a bit is, and its link with bytes. Edexcel include the quantity nibble. Know that prefixes can be used in quantities of bytes and know the prefixes, names and symbols for kilo, mega, giga and tera Binary arithmetic Be able to add up to three binary numbers. Be able to apply a binary shift to a binary number. Edexcel do not impose limits on binary addition. Edexcel expects an understanding of overflow. Edexcel expect both logical and arithmetic shifts Character encoding Understand what a character set is, be able to describe 7- bit ASCII and Unicode. Edexcel only covers ASCII, and does not specify 7-bit or 8-bit extended ASCII Representing images Describe size in pixels and colour depth for bitmaps. Describe how a bitmap represents an image using pixels and colour depth. Edexcel request students understand how bitmap images are represented in binary, and refer to pixels, resolution and colour depth. Edexcel request students understand how bitmap images are represented in binary, and refer to pixels, resolution and colour depth.

9 3.3.7 Representing sound Understand that sound is analogue and must be converted for storage and processing. Edexcel request student to understand how sound is represented in binary, and refer to it being analogue Data compression Topic are Explain what data compression is, why data may be compressed and that there are different ways to compress data. Explain how RLE can be used. Edexcel include JPEG and MP3 as examples and use the terms lossy and lossless. Edexcel expect a student to know how a lossless RLE algorithm works. Represent data in RLE frequency/data pairs Hardware and software Define the terms hardware and software and understand the relationship between them. Not specifically covered by Edexcel, although roughly analogous with Boolean logic Construct truth tables for NOT, AND, OR logic gates Software classification Understand the need for and Similar expectations to AQA with a less

10 functions of OS and utility programs including key elements of OS management. rigorous list of key elements Systems architecture Explain the Von Neumann architecture. The role and operation of main memory, ALU, control unit, clock and bus are to be explained. Understand and explain the fetch-execute cycle. Understand the difference between main memory and secondary storage, as well as RAM and ROM. Understand why secondary storage is required, be aware of types, explain operations of SSD, optical and magnetic storage and discuss advantages and disadvantages. Explain the term cloud storage and explain advantages/ disadvantages compared to local storage. Understand the term embedded system and explain how it differs from a nonembedded system. Similar expectations to AQA with addition of input and output devices. Edexcel include cache. Edexcel cover as a concept without the advantages/disadvantages being covered. 3.5 Fundamentals of computer networks Define and discuss computer networks including benefits and risks.

11 Describe main types of network PAN/LAN/WAN. Understand and discuss wired versus wireless networks including benefits and risks. Explain the star and bus topologies. Define the term network protocol. Similar expectations to AQA although PANs are not covered. Edexcel cover C/S and P2P which AQA do not. Similar expectations to AQA although Edexcel do not cover benefits and risks. Similar expectations to AQA although Edexcel also cover ring and mesh network topologies. Explain the purpose and use of a set range of common network protocols. Understand the need for, and importance of, network security. Explain a set range of network security. Describe the 4 later TCP/IP model. Similar expectations to AQA although Edexcel use the term 'be able to use'. Edexcel only cover the concept of packets and refer to TCP/IP ad a method of doing this. 3.6 Fundamentals of cyber security Be able to define the term cyber security and its main purposes Cyber security threats Understand and be able to explain a set list of cyber security threats. Explain what penetration testing is and what it is used for. Similar expectations to AQA although Edexcel have a wider range of methods of identifying vulnerabilities.

12 Social engineering Define and describe social engineering, how it can be protected against, and explain a set list of forms Methods to detect and prevent cyber security threats Understand and be able to explain a set list of security measures. 3.7 Ethical, legal and environmental impacts of digital technology on wider society, including issues of privacy Current ethical, legal and environmental impacts and risks of digital technology on society including data privacy 3.8 Aspects of software development Testing Refers to use of test plans and data under developing code (2.1.4) Additional Content Our new specification also includes the following content which is not included in the. New specification (8520) reference Content Compare the efficiency of algorithms Be able to use random number generation.

13 Describe the structured approach to programming Explain the advantages of the structured approach Be able to write simple authentication routines Know about and be able to differentiate between machine code and assembly language Understand that ultimately all code written in high-level or assembly languages must be translated into machine code Understand that machine code is expressed in binary and is specific to a processor or family of processors Describe situations where binary shifts can be used Understand that character codes are commonly grouped and run in sequence within encoding tables Describe the purpose of Unicode and its advantages over ASCII. Know the link between Unicode and ASCII Understand what a pixel is and be able to describe how pixels relate to an image and the way images are displayed Describe using examples how the number of pixels and colour depth can affect the file size of a bitmap image Calculate bitmap image file sizes based on the number of pixels and colour depth Convert binary data into a black and white image Convert a black and white image into binary data Understand that sound waves are sampled to create a digital version of sound Describe the digital representation of sound in terms of sampling rate and sample resolution.

14 3.3.7 Calculate sound file sizes based on the sampling rate and the sample resolution Explain and be able to interpret Huffman trees Be able to calculate number of bits required to store Huffman coded data and uncompressed ASCII Construct and interpret truth tables for simple logic circuits Create, modify and interpret simple logic circuit diagrams Explain and give examples of system and application software Explain the effects of clock speed, cores, cache size and type on performance Define and describe malware, how it can be protected against, and explain a set list of forms. 3.8 Design (some reference in 1.2.1) 3.8 Implementation (some reference in and 2.1.1) 3.8 Evaluation/refining (some reference in 2.1.7) Competitor Specific Content The following topics are covered by Edexcel but are not included in our new specification. Area Content Understand how to identify and correct errors in algorithms Understand how to code an algorithm in a high-level language Be able to evaluate the fitness for purpose of algorithms in meeting specified requirement efficiently using logical reasoning [and test data] Be able to analyse a problem, investigate requirements (inputs, output, processing, initialisation) and design solutions.

15 2.1.1 Be able to write program in a high-level programming language Be able to differentiate between types of error in programs (logic, syntax, runtime) Be able to interpret error messages and identify, locate and fix errors in a program Be able to determine the strengths and weaknesses of a program and suggest improvements Understand the limitations of binary representation of data (sampling frequency, resolution) when constrained by the number of available bits Understand that file storage is measured in bytes and be able to calculate file sizes (note that AQA cover this in images, sound and compression, but not as a generality) 3.4 Understand the need for encryption. Understand how a Caesar cipher algorithm works. 3.5 Databases Be able to produce logic statements for a given problem Understand the purpose and functions of utility software (managing, repairing and converting files; compression; defragmentation; backing up; anti-virus, anti-spyware) Understand how software can be used to simulate and model aspects of the real world Understand that network data speeds are measured in bits per second (Mbps, Gbps) Understand security issues associated with the 'cloud' and other contemporary storage. (Covered in although not explicitly) 5.3 The Internet and the world wide web.

16 Structure All specifications consist of a mix of examined and non-examined content. In all of the new specifications 100% of the marks are assessed by exam. 3 Components: Paper 1: 1.5 hours, 80 marks, 50% of GCSE. Mix of multiple-choice, short answer and longer answer questions assessing a student's practical problem solving and computational thinking skills. Paper 2: 1.5 hours, 80 marks, 50% of GCSE. Mix of multiple-choice, short answer, longer answer and extended response questions assessing a student's theoretical knowledge. Programming project: Report totalling 20 hours of work.? Components: Component 1 (1CP1/01): 1 hour, 40 minutes, 80 marks, 50% of GCSE. Mix of multiplechoice, short open response, open response and extended open response. Covers all topics. Focus on principles of Computer Science. Component 2 (1CP1/02): 2 hours, 80 marks, 50% of GCSE. Mix of short open response, open response and extended open response. Based on a scenario, focus on application of Computational Thinking. Component 3 (1CP1/3A-3E) Programming project: 60 marks, 20% of GCSE. Report totalling 20 hours of work.

17 Assessment objectives Note, all of the new specifications (first teaching September 2016) must use the AOs and weighting as used by our specification Assessment objective AO1 Demonstrate knowledge and understanding of the key concepts and principles of computer science AO2 Apply knowledge and understanding of key concepts and principles of computer science AO3 Analyse problems in computational terms: to make reasoned judgements; and to design, program, evaluate and refine solutions % Marks