We report and comment on a recent experience of laboratory teaching carried out with a group of pupils of a primary school within the STEM2020 project, whose purpose was to give a very simple introduction to the binary system and to the functioning of computers to carry out the basic mathematical operations. Using the concept of “full / empty” and a few “rules of the game”, the pupils were guided to create a spreadsheet, or more generally, a mechanical calculator. The use of this mechanical calculator was shown to be suitable for everyone, even the youngest pupils of primary school, who lack basic math and calculus skills. The other students instead could verify its good functioning using the correspondence table between the binary coding of numbers and their standard representation in the decimal system.
