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ARMlite – a new online processor simulator

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Last edit: 05 October 2022

Many teachers have made use of my earlier simulators for LMC and for an AQA-compatible processor. ARMlite has evolved from the latter, and offers:

  • A new, cleaner user interface
  • Much more memory (1 MB).
  • Much higher performance (1-10 million instructions per second, depending on your browser and computer)
  • Debugging facilities, including single-step, slow running, and breakpoints.
  • Simultaneous representation (via tooltips) in Hex, Binary, and Decimal.
  • Extended instruction set, including subroutines, stack operations, indirect and indexed addressing
  • Interrupt handling, from multiple simulated sources (keyboard, mouse, timer and pin)

You can access ARMlite here: – If you want to see an instant demonstration of what ARMlite is capable of, use our ‘Easter Egg’: click Edit, then type the word demo into the Program area, and then click Submit. You’ll see a high-speed implementation of Conway’s ‘Game of Life’.

ARMlite is the result of a two-year collaboration with Richard Pawson, that has also resulted in a new book on Assembly Language programming for A-level pupils, downloadable here. Attached to this resource (and also linked from the ARMlite page under Documentation) is the Programming Reference Manual.

Why have we done this, when the earlier AQA simulator already simulated the full AQA assembly language specification (using our ‘skill and judgement’ where the latter is ambiguous)?

The first answer is that these additional capabilities simply make learning assembly language more interesting.

The second is that these capabilities help reinforce a pupil’s understanding of several other aspects of the syllabus – this is brought out clearly in the book.

Thirdly, we have designed ARMlite specifically as a platform to enable pupils to write their NEA projects in assembly language, if they are so motivated. Both Richard and I believe that – for some pupils – this is both a viable, and potentially very enjoyable, option.


If you find any bugs in ARMlite, please email them directly to me. Please also feel free to post general feedback on ARMlite, here. To give feedback or report errors specifically on the book please see that resource page

Edit history

Peter Higginson | 05.10.22

Added some more recent documents