Abstract

This memory is a function from names to values (i.e. numbers). Inputs too are modelled by functions from names to values. It is assumed that at each moment the environment specifies a value ' i for each input i, i.e. it determines a mapping ' : name ! N, that varies with time. For any particular system there will only be a small finite number of inputs (in1, in2, req and reset for Mult), but this fact does not need to be builtin to the general theory. It will be assumed that some state variables are readable by the environment (avail and out for Mult). During each cycle of execution of M, an instruction is selected and executed, resulting in a new state. If the instruction is an input, then this new state will depend on the inputs supplied by the environment. In what follows, it is first shown how the program MultProg in Section 1.1.3 determines a machine and then how the informal specification Mult in Section 1.1.2 can be expressed as a predicate on machines. Finally, a method is outlined for proving that programs meet specifications and it is illustrated using MultProg and Mult. 1.3. Determining a machine from a program

Citations