abaci

Why is the abacus frequently cited as the earliest computer?  It
doesn't satisfy a single definition of a computer.  It doesn't
automate anything.  It's not a general purpose computer in that
it cannot be programmed.  Its output is always the same as
its input.  It has a finite memory but no control.  IT'S JUST
BEADS AND STICKS!  Essentially, an abacus was just a way of
keeping records without paper or a useful number system, but
a computer, I think not.

An abacus is no less a computer than our electric powered programmable computational devices that are based model after the von Neumann machine. Together with your brain and the abacus, you too can process computer programs just like these electronic von Neumann machines.