A virtual experience on the very first Italian computer

Despite their temporal proximity, the technologies of the early computers are far from us. Yet, they are part of the history of science and technology, and they deserve to be studied and popularized. Being machines made to run software programs, they should be exhibited running. Unfortunately, old machines still in working condition are extremely rare. Restoring or rebuilding an old computer is a hard, expensive task: the original components are rare, and the technology is forgotten and sometimes lost. The research needed to re-understand those computers has to adopt experimental archaeology methods: rebuilding old hardware/software requires proceeding by hypotheses and experiments. However, a rebuilt or restored computer is a unique exemplar and a precious specimen: it is not suitable to let people interact with it. A more flexible solution is to use software simulations. First of all, simulation is a valuable tool to carry out the experiments needed to study past technology. Second, the simulators are virtual replicas that let people fully understand the old machines by interacting with them without jeopardizing those precious relics of the past. This article presents the virtual rebuilding of the first computer made in Italy: the Macchina Ridotta (MR) of the University of Pisa. The MR was dismantled after few months of intensive usage to cannibalize the materials for a second computer. As a consequence, the MR disappeared from later chronicles and for many years was ignored by historians. When we attempted to reconstruct the MR history, we found that the survived documentation was far from complete. Simulation proved to be the key tool to support the experimental approach adopted for understanding the MR technology, rebuilding it, and assessing its achievements. The MR simulator is now used at the Museum of Computing Machinery of Pisa as a mean to truly experience a working session on the MR-a typical computer from the 1950s. The exhibit and the workshops, by exploiting the accurately reproduced characteristics of the MR, address popularization of computer science from several perspectives: from technological mechanisms to scientific foundations, passing through the representation of computers in popular culture