What is Turing's Comparison between Mechanism and Writing Worth?

In one of the many and fundamental side-remarks made by Turing in his 1950 paper (The Imitation Game paper), an analogy is made between Mechanism and Writing. Turing is aware that his Machine is a writing/re-writing mechanism, but he doesn’t go deeper into the comparison. Striding along the history of writing, we will hint here at the nature and the role of alphabetic writing in the invention of Turing’s (and today’s) notion of computability. We will stress that computing is a matter of alphabetic sequence checking and replacement, far away from the physical world, yet related to it once the role of physical measurement is taken into account. Turing Morphogenesis paper, 1952, provides the guidelines for the modern analysis of “continuous dynamics” at the core Turing’s late and innovative approach to bio-physical processes.