Hi;
I should not be writing this, but I believe I am not completely wrong. Otherwise, please, correct me.
Again, I do not own an HP97, but I understand that printing numbers will never burn or kill the printhead; otherwise, if you think that NNN (Non-Normalized-Numbers) are numbers out of the range 00002 to 10012, then they are probably in the range 10102 to 11112, what is logically acceptable if we think ASCII code, not BCD. Please, consider that I do not have any idea if this is possible or not, I'm just thinking about electronics, HW, SW and the burning head.
If the calculator (HP97) does not offer the standard input for these "numbers" (A16 to F16), then many things can happen if they appear in any register. Even "burning" or "killing" the printhead when one attempts to print them, and it may happen as a consequence of (for example) not turning off the head "burners" (resistors). As the NNN are not expected, the printhead controller may simply fail. Agree?
The "head burning" is a fact, and some guys in here have had the (sad) experience of seeing this happening.
Cheers.