Resources for Teaching OCR J277

Topic

Links

Notes/Explanation

1.1

Systems Architecture:

• how programs are stored
• what's in the Arithmetic Logic Unit?
• impact of word-length / bus width

• There are no interactive resources to enable students to visualise the fetch-execute cycle, but there are slides, links to videos, etc., on the resources page.
• It's also a representation topic, but I explain that the FDE cycle works because programs are stored as numbers which represent a particular instruction to be performed. That's why the RAM can store both data and instructions.
• I make the link between the ALU, logic circuits and binary addition by explaining to students how a full adder can be used to add bits.
• The size of the registers and width of the buses affect the number of instructions that can be performed, the size of numbers that can be handled, and the number of memory locations that can be addressed.

1.2

Memory and Storage:

• storage media
• units
• data storage:
  • numbers
    • number base abacus
    • binary
    • binary counter
    • binary flags
    • binary game
    • binary addition
    • range of binary values
    • hexadecimal
    • convert directly between binary and hexadecimal
  • characters
    • ASCII and Unicode values
    • how the symbols can be stored
  • images
    • colours (using RGB)
    • colours (using HSL)
    • bitmaps
    • manipulating images and the impact of colour depth (see also range of binary values)
    • the need for metadata
  • sound
    • recording sound waves
    • the effect of sampling rate and sampling sound (see also range of binary values)
  • compression
    • effect of reducing colour depth (lossy)
    • effect of reducing sample size (lossy)
    • RLE and Huffman Coding (lossless)

• There are no interactive pages for storage media and their properties, but students should be aware of representation topics that that they understand how programs, images and sounds are stored. There are slides available on the resources page, including ones that discuss cloud storage and fragmentation.
• The binary page can be used to demonstrate shifting, the maximum value in a given number of bits, etc.
• The binary counter page shows the "history" of each bit so can be used to demonstrate a quicker way to write a sequence of binary numbers (or fill in a truth table).
• The binary addition page also shows overflow - you can use the binary page to demonstrate underflow by shifting numbers rightwards.
• ASCII and Unicode values are used to store which character is being used, e.g. an A, and not what it looks like.
• You can use the metadata page to demonstrate that the colour of the pixels isn't enough information to be able to reconstruct the image.
• With the sound recording page you can zoom in until you can see the individual samples and show just how many there are per second.
• The sampling pages shows you what happens if the sampling rate is too low, and the effect of reducing the sample size.
• The specification says only that students should know that colours are stored as a unique code - it doesn't actually mention RGB (although most people don't bother with HSL).
• For a broader view of representation you could also look at vector graphics, programs and other forms of representation.
• To aid understanding of what is "lost" in lossy compression you can use the two pages listed to show the impact of reducing the sample size both on the image or wave (see also range of binary values) and on the file size.
• Details of Run-Length Encoding and Huffman Coding aren't required for OCR, but students might be interest to see how lossless compression might work.

1.3

Computer networks, connections and protocol:

• parity "trick"
• parity "trick" with 0s and 1s

• substitution ciphers

• There are no interactive resources to enable students to visualise networking, but there are slides, links to videos, etc., on the resources page.
• Parity isn't required, but you might want to discuss how errors are detected and why certain transmission media, e.g. fibre optic cables, have greater bandwidth.
• As well as demonstrating substitution ciphers using the linked page, we also do programming tasks, e.g. shift ciphers and encryption with EOR.

1.4

Network security:

• SQL injection
• encryption

• I show students this video to help them to visualise what's happening in the different forms of cyber attack.
• After we've looked at SQL we look at the SQL injection page see whether we can use a username and password that creates a value SQL statement that is always true (the examples in Wikipedia work).

1.5

Systems software

• There are no interactive pages for systems software, but there are slides available, including an animation of defragmentation, on the resources page.

1.6

Ethical, legal, cultural and environmental impact:

• answering these questions
• news stories to illustrate answers

• Throughout the course we look at issues as they arise in the news (the sort of news stories that I post via Twitter, Threads and Bluesky).
• As it's difficult to predict exactly what will appear, we also discuss points that we could make for almost any context.

2.1

Algorithms:

• standard searching algorithms
  • compare linear and binary search
  • binary search game
  • binary search program (the output shows how to answer a binary search question)
• standard sorting algorithms
  • bubble sort game
  • bubble sort program (shows how to answer questions)
  • insertion sort game
  • insertion sort program (shows how to answer questions)
  • merge sort game
  • merge sort program (shows how to answer questions)
  • comparing sorting algorithms
  • sorting balance

• Look through the Algorithms menu for more examples of algorithms that you can discuss with your students.
• More confident programmers can respond well to discussions of recursion, e.g. the flood fill algorithm

2.2

Programming Fundamentals:

• programming concepts and data structures
  • programming revision guide
  • Python basics / introductory tasks
  • practice tasks
  • OCR Coding Challenges - possible solutions
• Boolean logic (see below)
• SQL
  • Computer Shop SQL Task*
  • Bike Shop SQL Task*
  • Stolen Gemstones SQL Task*
  • SQL injection
• random number generation
  • random numbers
  • Monte Carlo method
  • trees in Scratch (using randomness to make them look less artificial)

• The programming resources aren't interactive resources themselves but I use them to do at least one programming task every week throughout the course, plus additional programming in theory lessons to reinforce the content - e.g. conversion to and from binary and hexadecimal or encryption. Look in the Programming and Algorithms sections for further ideas of things that you can program.
• You can use the Monte Carlo method to show that random numbers aren't only for games, etc.
• Windows users can use the SQL view in Microsoft Access to investigate SQL.

2.3

Producing robust programs

• There are slides, test-plan templates, etc., on the resources page.

2.4

Boolean logic:

• Boolean operators (interactive)
• Boolean logic (inc. truth tables)
• logic circuits
• the full adder (i.e. using logic circuits to add numbers)
• logic.ly*

• The binary counter and range of binary values pages can be used to show how many rows are required in a truth table and how to quickly fill in the inputs.

2.5

Programming languages and Integrated Development Environments

• There are no interactive resources for this topic, but look at the resources page for presentations, etc.