  In particular, a section of (Turing 1948) is devoted to a general classification of ‘machines.’ The period between 1937 and 1948 had given Turing much more experience of actual machinery than he had in 1936, and his post-war remarks reflected this in a down-to-earth manner. Turing distinguished ‘controlling’ from ‘active’ machinery, the latter being illustrated by ‘a bulldozer’. Naturally it is the former—in modern terms ‘information-based machinery’—with which Turing's analysis is concerned. It is noteworthy that in 1948 as in 1936, despite his knowledge of physics, Turing made no mention of how quantum mechanics might affect the concept of ‘controlling’. His concept of ‘controlling’ remained entirely within the classical framework of the Turing machine (which he called a Logical Computing Machine in this paper.)