The way that the author uses pure Excel formulas (no VBA or macros) to compute a QR Code from scratch is similar to how I used pure Excel to compute ciphers:
That's really cool. I've been wanting to delve into the inner workings of ciphers for some time and I think this will make it easier.
Thanks! I have another piece of work that shows the internal computations. I implemented hashes and cipher in short Python code. You can insert debugging prints easily to show the intermediate values. https://www.nayuki.io/page/cryptographic-primitives-in-plain...
(Pure) Excel is a form of dataflow programming --- the sequencing is implicit, but the flow of values is explicit. For algorithms that don't have arbitrary input-dependent looping, it is relatively easy to implement.
Excel - the handy old school swiss army knife for data processing and visualization. Its pretty interesting what some folks can pull of with it.