>         If multiple '=' signs are allowed then the controller *MUST* be a
> separate *MASTER* block.  If so then the possibility of varying 'grades' of
> master arises, with differing features, giving rise to a whole range of
> incremental maths machines (sort of like Ford sells small cars, large cars,
> small trucks and large trucks).
>
>         I say create a definate master block with an LCD display panel that
> gives feedback (and, in more advanced models - advice and hints).
>
>         Bye.

Actually, no, I think each "=" block can be smart;

Each "=" block should tell the "=" blocks, if any, to each side of it,
that it's a "terminator", as anything the other side of an Equals block
is none of it's business, math-wise!  (Queries generated by some other
"=" block should be easy to recognize, too.)  It'd be perfectly legal,
and NECESSARY, to have this work properly:

  5 != 4 != 3 != 4 != 6 = 6

  The first 4 "Equals" signs should be slashed (inequality), I'd think
of 2-3 red LED's at an 80 degree angle (& in series so they only use one
PIC output pin <G>), to signify an error;  The last equals sign would
say, "All is well", though.  The bars in the "=" sign could be red/green
LED's, if desired, is one thought.  So you get green "=", or red slashed
"=", depending on the equation;  Maybe use alternate flashing the green
horizontal bars & the red slash for a syntax error?  <G>

If you have one master block, you'll need all power to be fed through it
(Could just use a track that the "=" signs plug into, and perhaps slide
on (like track lighting tracks?), to feed power to all the rest), power
coming from just one place with 25 resistive connections to the end of
the circuit gives you power distribution and ground lead lifting
problems, potentially.  Of course, the only "major" current used here
will be at an equals sign, all other currents are pretty small, really.
OTP 12C508A's for most blocks, I imagine?  <G>

  Mark