Think you know your HP-41?

[Gene]

This is from the past, but fun. :-)

Do the following:

shift GTO . .
PRGM (on)
shift LBL ALPHA QUARK ALPHA
PRGM (off)
ALPHA
, (just type a comma)
shift ASTO ST X
PRGM (on)
PRGM (off)

Why does the display show what it does? I thought all we typed was a comma?

[Thomas Okken]

Neat! It works with period and colon, too. And the other text doesn't have to be a program line, either:

ALPHA : ASTO X CLA ABCDEFGHIJKL ALPHA

shows _:

ALPHA ALPHA

now shows L:

[Ángel Martin]

he, he, ... peculiar little bugger indeed. Not a bug, since the phantom char is *not* really in the X-reg (only shown on the LCD) - so if you do X<>Y, X<>Y it's gone. But it's back there after pressing PRGM twice like the first time.

Playing around a little more we see it's the last ALPHA character "sticking" to the LCD, "K" from LBL "QUARK" but also happens with LCD flashing messages on startup. The only condition for it to happen is that X has the radix character, so this is a parsing error (but not a bug!). Remarkable, time to look at the source code....

[Gene]

V10N7P19 of the PPC Journal is where I found this.

It was certainly not original with me, but I thought it interesting. :-)