56-bit representation of numbers vs. what is displayed

[brianrhill]

Thanks! That makes a ton of sense. It means the display isn't always determined from what is in register X (also known as C). Sometimes it is showing a non-normalized value cooked up from A and B. My simulation job just got harder :)

EDIT/PS: Your explanation helped me home in on this information in Francois Roulet's re-creation of Jacques Laporte's site (the specific page is http://home.citycable.ch/pierrefleur/Jac...te/A&R.htm):

The A register is setup to hold the displayed number with the digits in the proper order.

The B regis­ter is used as a masking register with digits 9 inserted for each display position that is to be blanked and a digit 2 at the decimal point location.

The decimal point is not allocated a register position; but it has a full digit position in the output display : one digit and the decimal point share one of the 14 digit times.

When the anode driver of output display unit detects a decimal point code during T4, it provides a signal to the cathode driver of the output display unit to move to the next digit position.

The digit 9 mask in register B allows both trailing and leading zeros to be blanked (i.e., by programming 9's into the B register).

Use of all three working registers for display (the C register to retain the number in normalized form, the A register to hold the number in the displayed form, and the B register as a mask) allows the calculator to have easily both a floating point and a scientific display format. This scheme will be used in all Classic & Woodstock calculators.