[asciimov]

Over the years we have evolved the meaning of computer from something that calculates or reckons to a electronic device that runs software. In reality any black box that has a one-to-one relationship between inputs and outputs can be considered a computer.

It might be easier to think of mechanical computers, such as the WW2 fire control computers aboard Navy Ships[0] or more famously the Antikythera mechanism[1]. These are fixed devices, they compute values from inputs. The "program" is stored in the gears camshafts and differentials and ratios between them.

Similarly, fixed digital computers such as the Nimatron have their operations stored in relays and digital logic. These sorts of computers don't have a list of instructions. They just have schematics, inputs going through electronic circuits that wind up at outputs. You can do a lot of calculating with just simple logic gates.

[0] - https://www.youtube.com/watch?v=s1i-dnAH9Y4

[1] - https://en.wikipedia.org/wiki/Antikythera_mechanism