The work referred to in the Introduction was presented by M. Pacelli and U. Picciafuoco to the annual meeting of the Italian Computer Society (A.I.C.A., Convegno di Bologna, 1963) under the title ‘Descrizione ed uso della macchina astratta didattica’ (Description and use of the abstract didactical machine). Among the most recent contribution to the field one may also recall ‘The “Model T” Computer’, by AmesW. F. and RobinsonJ. A. [J. Engng Educ.54, 338–344 (June 1964)].
