TI 58/59 ROM modules and OP instructions

[Didier Lachieze]

(12-31-2017 07:37 PM)Dieter Wrote:  That's exactly what I think. Either it is this, or maybe the other possible explanation that assumes the ROM programs have been written before the final calculator design including the OP commands was fixed.

The Math Utility CROM (#10) was released in 1979, well after the introduction of the TI-59, according to SR-52 Notes V3N8p5,6 :

Quote: Many of the programs in this new CROM do indeed reflect
better programming quality than has gone into earlier ones

So it may be worth checking if it contains any OP instruction.