HP Key Notes

When the HP67 handheld programmable calculator came on the market back in 1976, I was the first person worldwide to develop a program for calculating sunrise and sunset for any point on the globe for a given date. Up to a latitude of 50 degrees, the calculated times were accurate to 10 seconds.

I also became interested in calculating special functions for the HP67 (and the HP97 desktop calculator). I regularly sent my programs to the Hewlett Packard Users’ Program Library Europe in Geneva. The best European programs were made available to users world-wide through the HP Users’ Program Library in the US. Some of these programs were presented in HP Key Notes (see facsimile to the right). With the advance of PCs, handheld calculators disappeared and with it the users’ program libraries. My interest in special functions waned and, unfortunately, I did not rewrite the programs in C.