Where is NOP on the HP-67 ?

[Dave Britten]

(01-07-2021 10:36 PM)Gene Wrote:  Gene: You are quite right, Valentin! An "A" in an HP-65 program is equivalent to GSB A or XEQ A.

Wanted to state this for the record even though the program now works.

And sometimes it's equivalent to GTO A, if the lone A is encountered while already inside a 2nd-level subroutine. And if LBL A doesn't exist anywhere in the program, it has some other rather unique - and useful - behavior that surprisingly isn't a label-not-found error.

The 65 is a rather odd beast in quite a few ways. For additional fun, take a look at the HP 65 hyperbolic functions program in 65 Notes/PPC Journal (don't have the issue number in front of me - I'll dig it up if nobody else finds it). See if you can figure out how the calls to LBL C work, and why the program contains these three steps which DON'T result in an infinite loop/stack overflow:

LBL
C
C

It's sometimes rather tricky to convert 65 programs to newer machines because of all these really interesting quirks that were exploited to their fullest.

Another interesting trick:

g
DSZ
NOP
GTO
A