I recently needed to buy a new calculator for my engineering degree. While comparing the different models, I was shocked that there is almost no mid-range calculator in term of functionalities. Either you buy a basic one, or a very expensive high-end one with loads of functions you will never use. Moreover, some college students are facing the problem that the allowed functionalities on their calculators vary from an exam to another (for example whether graphical calculators are allowed or not), forcing them to constantly change the calculator they use.

The solution : a modular calculator.

• The base calculator would be similar to any high-school suitable one.
• There would be the possibility to add modules depending on specific needs (i.e. graphic display, unit conversions,...).
• The modules would be stackable in order to create the ultimate calculator, tailored to your needs.
• Everything would be open (source & hardware), with an easy and well-documented interface in order to allow anyone to create their own modules if needed.
• This implies easy functions to create interfaces within the built-in screen, an easy way to access the last result and stored variables, the detection of the other connected modules and the possibility (if provided by the module) to interact with them.
• There would be the possibility to sell a development module, which would consist of a hardware with standard buttons, an ICSP header to program it and a template code.