DM-xxCC Default Display Values

[Mark Hardman]

Michael has really improved the look of his web site at http://www.rpn-calc.ch/. The home page now features a carrousel of all five calculator models.

Mindlessly spinning the calculators, I started wondering why he chose the various default display values for each model:

DM-10CC = 1.7321

Easy, 3 SQRT

DM-11CC = 1.4142

Again easy, 2 SQRT

DM-12CC = 1.55

The best I that I can come up with is: 111 LN LN

DM-15CC = 1.6180

Pure gold, 5 SQRT 1 + 2 /

DM-16CC = AA55 H

Again, no idea: 

BIN 1010101 Enter Enter 1001 RLn + HEX

or

HEX 55 Enter Enter 9 RLn +

Does anyone have a better solution for the DM-12CC or DM-16CC? Maybe Michael could give us the real answers.

Mark Hardman

[Cristian Arezzini]

About the "AA55": don't think too much about mathematics there, remember it's a programmers' calculator. And "AA" and "55" are two bytes often used for memory testing, as they have a peculiar bit pattern - AA is 10101010 and 55 is 01010101. So it might just be a tribute to old-style computer programming, which is what the 16C was for.

[Dale Reed]

It goes back even further than that. In the old Teletype days (Western Union Telex et al), they used to send a line of "RYRYRYRYRYRYRY"... in order to "exercise" the send and receive contacts. These machines use the old 5-level (5-bit) "Baudot" code. R and Y are the TTY equivalent of 0xAA55 for memory tests --- their bit patters are 01010 and 10101 (but I don't remember offhand which is which).

They especially look nice punched into paper tape!

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Dale, W8ABZ

(Don't ask how many Teletype (R) Model 19ASR, 28ASR and 32ASR machines I fixed back in the radio club in college days....)

[Lode]

I wonder what the keys of the ones with titanium housing will be like!