Test this combination of keys on your HP-48 (mine is a GX one) and discover a secret grid of cross words hidden inside (various fornames) :
ON
[right shift] ENTRY [right shift] ENTRY
(this turns the calculator into ALG PRG mode)
[alpha] [alpha] RULES [ALPHA] [ENTER]
and then appears on the screen these mysterious crosswords...
Funny !
(by the way, I was learning how to rearrange some symbolic expressions when I discovered this)