4-level stack manipulation on 12c

[Don Shepherd]

Thanks for all those tests, Bob.

I've got two 12c's. The original slow (but stable) one from around 2001 I think, and then the super-fast 12c+ I got from a fellow out west (where they were initially available at some store out there) when they first came out a few years ago. Although very fast, it has an issue or two with the self-test, as I recall. I have Dave Britten's prime factor finder (which I modified to run on the 12c+) loaded on the fast one and it is one of the fastest prime factor finders on any calculator I have seen.