In the 1970s, mathematician Georges Papy developed a physical educational tool known as a mini-computer. It consists of a set of four cards, each featuring four colored cells, and a collection of tokens. The device serves as a tangible model for binary-coded decimal (BCD) encoding, where each card functions as a 4-bit register.
The system uses a positional notation where cells within any card represent values of 8, 4, 2, and 1. While each card can physically hold values up to 15, the rules of the game limit each cell to one token and each card to a maximum value of 9. This constraint forces users to perform carry operations, mimicking hardware BCD normalization.
The educational method focuses on hands-on manipulation rather than abstract lectures. By moving tokens between cards, children observe how shifting a token to a new card increases its value tenfold. This exercise demonstrates the carry bit process, where an overflow in one nibble triggers a shift to the next higher-order register.
Through iterative exercises, students learn to represent numbers by summing the values of occupied cells. The process progresses from basic single-digit representations to complex multi-digit numbers, such as 2863, which is decomposed into hardware-like bit registers. This approach allows children to grasp positional systems through physical interaction.
