The Machine's Path Depends on Data
Among the processor's few actions, one has been waiting quietly since its lesson: choose which action to perform next. Today it steps forward. Combined with comparison, it gives the machine something no calculator has — a path that is not written down anywhere, but born at run time from the meeting of program and data. This lesson is where machines stop being player pianos.
Start with the question
A music box plays its pins in order — always the same tune. The idealized machine also performs actions in strict sequence, one per tick. So: is the machine a music box? Where would different behavior on different days even come from?
From two bricks meeting. The processor can compare two numbers. And the processor's marker — its place in the row of command-cells — is itself changeable: the action "choose what's next" moves the marker, to one address or another, depending on the comparison's outcome. That is the entire mechanism, and it deserves slow reading: the program text contains BOTH continuations, written once and forever; which one runs is decided at run time by whatever numbers the comparison happens to meet. The text is fixed; the path through it is not.
Nothing here violates the clock: still one action per tick, still strict sequence — the sequence of performed actions is as orderly as ever. What changed is that this sequence is no longer a copy of the text's order. Two runs of one program are two different journeys through the same country.