Switching to AQA from OCR

Transcription

1 Switching to AQA from OCR This resource compares our new GCSE Computer Science specification (8520) with the new OCR Computer Science specification (J276). If you are thinking of switching from OCR 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 OCR GCSE Computer Science specification (J276) 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. Determine the purpose of simple algorithms. OCR has similar expectations without explicitly mentioning pseudo-code and flowcharts Searching algorithms Understand and explain linear search.

2 Understand and explain binary search. Compare and contrast linear and binary search algorithms. OCR do not explicitly compare and contrast Sorting algorithms Understand and explain merge sort. Understand and explain bubble sort. Compare and contrast merge and bubble sort algorithms Data Types OCR does not explicitly compare and contrast. Understand the concept of a data type. 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

3 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 Arithmetic operations in a programming language Be able to use addition, subtraction, multiplication, real division, integer division including remainders. OCR has similar expectations, with the addition of exponentiation 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. OCR has similar expectations Boolean operations in a programming language Be familiar with and be able to use: NOT AND OR.

4 3.2.6 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 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.

5 Subroutines (Procedures and Functions) Understanding the concept of subroutines. Explain the advantages of using subroutines in programs. Describe the use of parameters to pass data within programs. OCR cover procedures and functions but do not explicitly go in to as much detail as AQA. Use subroutines that return values to the calling routine. Know that subroutines may declare their own variables, called local variables, and that local variables usually: 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 Robust and secure programming Be able to write simple data validation routines. Be able to write simple authentication routines. Be able to select suitable test data (normal, boundary, erroneous) and justify the choice.

6 Classification of programming languages 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 Number bases OCR has similar expectations (referred to as characteristics). Understand decimal, binary and hexadecimal. Understand that computers use binary to represent all data and instructions 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.

7 3.3.3 Units of information Know what a bit is, and its link with bytes. Know that prefixes can be used in quantities of bytes and know the prefixes, names and symbols for kilo, mega, giga and tera. OCR has similar expectations with addition of nibble and petabyte Binary arithmetic Be able to add up to three binary numbers. Be able to apply a binary shift to a binary number Character encoding Understand what a character set is, be able to describe 7- bit ASCII and Unicode Representing images Understand what a pixel is and be able to describe how pixels relate to an image and the way images are displayed. Describe size in pixels and colour depth for bitmaps. Describe how a bitmap represents an image using pixels and colour depth.

8 Describe using examples how the number of pixels and colour depth can affect the file size of a bitmap image Representing sound 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 Data compression Topic are Explain what data compression is, why data may be compressed and that there are different ways to compress data Boolean logic Construct truth tables for NOT, AND, OR logic gates. Construct and interpret truth tables for simple logic circuits. Create, modify and interpret simple logic circuit diagrams. OCR has similar expectations (not specifying as logic circuit diagrams).

9 3.4.3 Software classification Explain and give examples of system and application software. Understand the need for and functions of OS and utility programs including key elements of OS management. OCR cover systems software but not application software Systems architecture Explain the Von Neumann architecture. The role and operation of main memory, ALU, control unit, clock and bus are to be explained. Explain the effects of clock speed, cores, cache size and type on performance. 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. OCR goes in to more detail including specific registers, PC and accumulator. OCR has similar expectations with the exceptions of the clock and bus. OCR words this differently but appear to has similar expectations. OCR has similar expectations with the addition of virtual memory and flash memory. OCR has similar expectations, specifically covering capacity, speed, portability, durability, reliability and cost.

10 Understand the term embedded system and explain how it differs from a nonembedded system. OCR has similar expectations 3.5 Fundamentals of computer networks 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. 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. OCR has similar expectations with the exception of PANs. OCR has similar expectations, adding further detail to wireless networking. OCR covers the star and mesh topologies. OCR has similar expectations with a comprehensive list of threats. OCR covers the concept of layers without explicitly discussing TCP/IP. 3.6 Fundamentals of cyber security Be able to define the term cyber security and its main purposes. OCR has similar expectations with a comprehensive list of threats Cyber security threats

11 Understand and be able to explain a set list of cyber security threats. Explain what penetration testing is and what it is used for. OCR has similar expectations with a comprehensive list of threats. OCR has similar expectations with a comprehensive list of threats Social engineering Define and describe social engineering, how it can be protected against, and explain a set list of forms Malicious code Define and describe malware, 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 OCR has similar expectations, with more focus on specific legalities.

12 3.8 Aspects of software development Design Implementation Testing Evaluation/refining Additional Content Our new specification also includes the following content which is not included in the. New specification (8520) reference Content Explain simple algorithms in terms of their inputs, processing and outputs Understand that more than one algorithm can be used to solve the same problem. Compare the efficiency of algorithms Use nested selection and nested iteration structures. Use meaningful identifier names and know why it is important to use them Understand the concept of data structures (not explicitly covered by OCR) Be able to use random number generation Describe the structured approach to programming. Explain the advantages of the structured approach.

13 Know about and be able to explain differences between lowlevel and high-level languages. 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 Explain why hexadecimal is often used in computer science 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 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 is analogue and must be converted for storage and processing. 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. Explain how RLE can be used. Represent data in RLE frequency/data pairs Define the terms hardware and software and understand the relationship between them.

14 3.4.4 Explain the term cloud storage and explain advantages/ disadvantages compared to local storage. 3.5 Define and discuss computer networks including benefits and risks. Competitor Specific Content Define the term network protocol. The following topics are covered by OCR but are not included in our new specification. Area Content 1.1 OCR expects an overview of the purpose of the CPU which is not specifically required by AQA. 1.4 OCR specifically expect students to study factors that affect the performance of networks - this is not explicit in the AQA specification. OCR expect students to study Client-Server versus Peer-to- Peer networks. OCR expects students to study the hardware needed to connect computers in to a network. OCR expects students to study the Internet as a principle, including DNS, hosting and the cloud. OCR expects students to study the concept of virtual networks. 1.5 OCR expects students to study Wifi and Ethernet. OCR expects students to study the concept of packet switching. 2.1 OCR also covers insertion sort. 2.2 OCR expect students to be able to use SQL to search for data. 2.3 OCR expect students to plan for contingencies and anticipate misuse. OCR expect students to study maintainability, including

15 comments and indentation. OCR expect students to understand the purpose of testing, the types of testing, and how to identify syntax and logic errors. 2.5 OCR expect students to be familiar with the common tools available within an IDE. 2.6 OCR expect students to understand the use of metadata in an image file. 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. 3 Components: Computer Systems (01): 1.5 hours, 80 marks, 50% of GCSE. Written paper assessing a student's understanding of computer systems. Computational thinking, algorithms and programming (02): 1.5 hours, 80 marks, 50% of GCSE. Written paper assessing a student's computational thinking, algorithmic and programming skills. Programming project: totalling 20 hours of work.

16 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