Discreteness in computer programs
The reason for discreteness in computer programs is that the only real way we know how to construct such programs is using discrete logical structures. The data that is manipulated by programs can be continuous, as can the elements of their rules. But at some level one always gives discrete symbolic descriptions of the logical structure of programs. And it is then certainly more consistent to make both data and programs involve only discrete elements. In Chapter 12 I will argue that this approach is not only convenient, but also necessary if we are to represent our computations using processes that can actually occur in nature.