Are there more states in system systems than hardware?

Question

In “No Silver Bullet,” Fred Brooks claims that “software systems have orders of magnitude more states than computers”, which complicates their design and test (and the chips are already pretty hard to verify!).

This contradicts intuition: any working software system can be mapped to a computer in a certain state, and it seems that the computer may be in a state that is not a running software system. Thus, a computer must have much more potential states than a software system.

Does Brooks have any special meaning that I miss? Or does a computer really have fewer potential states than software systems that it can run?

Answer 1

Well, first think about Turing machines.

A Turing machine consists of an unlimited tape containing characters, a head and a small control unit, which is a finite state machine that controls how the machine reads, moves and changes characters on the tape.

: , , . : .

, .

, , , , , , , , .

, , , .. , : , , .

, , , . , : , .

---

, ... : .