Nenad: "However, its (the HP67's) set of programming instructions is certainly wider than the one of TI-59."
Gene: This is arguable. :-) I'm not aware of any programming instructions the TI58/59 are "missing" compared to the HP67/97.
Things the HP67/97 had that the TI-58/59 did not have:
1) Relative addressing (the I register holds a negative number, a GTO goes that # of steps backwards)
2) RPN (of course), which made many problems easier to program (in my opinion)
3) ?
Things the TI58/59 had that the HP67/97 did not have:
1) More than one index register (every memory could be used for indirect addressing vs. only the I register in the HP67/97)
2) More subroutine levels (6 vs. 3?)
3) ROM subroutines
4) Much larger program step and register availability, which meant some problems could be done on this machine that couldn't on the HP.
What else should go on these lists?