HP 41CX unusual display


Earlier today, my trusty 41cx apparently went into scientific display mode, and the decimal turned to a comma. Now that it is back in fixed mode, the decimal continues to appear as a comma, and the bottom row of the display is showing a small 0 and a 3.

Is this a malfunction, or have I inadvertently entered some weird display mode?

I have repeated turned it off and taken the battery pack out and put it back in. I have not replaced the batteries since I have never had a low battery warning.


The small 0 and 3 indicate that flags 00 and 03 are set. These are user flags, with absolutely no predefined significance to the calculator. Another flag (off the top of my head I want to say 29, but I'm sure somebody will correct me soon) controls whether the radix mark is set to the US or European standards (decimal point is period/comma, thousands separator is comma/period). Whichever flag this is, you'll want to toggle it.


Flag 29 controls display of thousands separator (set flag to display).

Flag 28 controls radix style (set flag for British/US style, clear for European).

So, for US and general usage, SF 28 and SF 29.


--- Les


Edited: 19 Jan 2012, 6:21 p.m.


Earlier today, my trusty 41cx apparently went into scientific display mode, and the decimal turned to a comma.

Basically, as already said, this all is a "phenomenon" which has its cause in the flag configuration and is completely harmless, although somewhat annoying.

More interstingly is that those flags were apparently switched inadvertedly. Usually, the flags for the numeric display (40 and 41) cannot be manipulated directly with the standard flag-manipulating commands (SF, CF).

Can you reconstruct what you have done to get this behaviour?



some event messed up the internal "REGISTER d" of your 41C. that register holds the status of the 41's system- and user flags.
i had this on rare occasions when plugging / unplugging modules, while leaving the calculator on (no good idea), or on very old machines with flaky internal contacts. just give your machine the standard ON/BACKSPACE treatment to reset all system/user flags to their default status.


Hello Bill,

As Hans said the flag register also known as the "d Register" was altered. This has happened to my 41CX on a few occasions to.
Here is what I did:

SF 28
SF 29

and TADA back to normal without losing any data.



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