Limit digit entry to width of LCD display

[ghewgill]

From Barry Mead:

I observed an unexpected behavior when playing with your calculator.
It seems that it allows you to enter numbers with precision greater than
10-digits.

For example if you enter a number:
-1.999999999! (10-digit number)

You will get one answer. If you enter:
-1.9999999999! (11-digit number)

You will get a different answer. If you enter:
-199999999999! (12-digit number)

You will get yet another answer even though the display cannot show
the extra 9's that you entered.