8 Dec
2010
8 Dec
'10
12:56 p.m.
On 12/8/2010 8:55 AM, Rick Bensene wrote:
Charlie C. wrote:
Hi Rick,
Thanks much for the explanation. I notice that the Toshiba BC-1212 has
one key labeled with both + and = so I'm guessing this was pretty common
in that time frame.
The CM, M+ and M- do seem very intuitive to me as long as the DP switch
is not set to blank.
BTW, my bad on Firefox, as I had failed to restart it after downloading
and installing Shockwave. After a restart the simulation works just
fine with Firefox.
Later,
Charlie C.
With the decimal point position set to blank, it
did seem to get stuck
looping in state 31 forever when I divided 1 by 3. It could also be
that I have no experience whatever with this calculator and this
behavior is quite normal. :-) I found it curious that the only +
function is to memory, and I found the M+ and MR operation to not be
intuitive but that's probably just my ignorance as well. Again, this
was with the DP position blank; maybe that is just not intended or I
don't understand it's purpose.
The blank position of the decimal point setting switch does cause odd
behavior in this class of machines. Why Sharp (who designed the guts
for many Facit calculators of this time) put a rotary switch in with a
position that led to incorrect operation isn't clear. Similar Sharp
machines exhibit the same behavior.
The really cool thing about Brent's simulations is that they are so
accurate that they properly reproduce this behavior. Brent's
reverse-engineering skills are truly epic.
To add, the "=" key is used. Enter a number, press "=". It is added
to
the display. For example, to add 16 to 45, enter 16, press "=", enter
45, press "=", and the answer is in the display. To subtract, just
enter the number to be subtracted, and press the "-" key. For example
to subtract 9 from the result, simply enter 9, then press "-".
Brent's simulation of the Facit 1123 does add the memory function keys
that don't actually exist on the Facit 1123 model. The circuitry is all
there for the memory functions, but on the actual machine, the keys
weren't on the keyboard. A different model (that cost more) included
the memory keys. The memory is a separate register that can be added to
or subtracted from. The M+ and M- keys add or subtract the number in
the display from the memory register.
The CM key clears the memory register, and the MR key brings up the
content of the memory register into the display.
Rick Bensene
The Old Calculator Museum
http://oldcalculatormuseum.com