Factorio Customizable Processing Unit.
Allow to write any logic on low level machine code.
The fCPU acts like a programmable microcontroller with a vector coprocessor that supports many useful instructions.
you can look at a custom implementation here https://gist.github.com/Katalliaan/8aee4b6dc1799a5ec3da9d702027826a
in base file there is plenty of examples at base/prototypes/tips-and-tricks.lua and simulations at base/prototypes/tips-and-tricks-simulations.lua which seems to use scripts like scenarios and mods
