In the early 1970s, HP built a small and exceptionally powerful calculator of engineers and surveyors: the HP-35A. This was nicknamed 'the electronic slide-rule' at the time, and it was designed to have all the functions of a slide-rule, plus additional capabilities, and to fit in a shirt pocket. It used Reverse Polish Notation (RPN) to simplify operation and allow the operator to see the intermediate results, and it took the scientific and engineering communities by storm!
So successful was the calculator that additional models were released: the HP-45, HP-55 and HP-65. The latter two were programmable, the HP-65 also being able to store and retrieve programs on magnetic cards. It was a back-up computer (the fourth) on the later Apollo missions.
After that, successive models included more features, better battery life, continuous memory, greater connectivity and more accessories for the connected models.
Over the years, many people developed programs for the programmable calculators and disseminated them. Starting with the HP-25, this produced many programs, and the successor calculators to the HP-25 used very similar programming structures and functions, allowing programs to be easily ported, from the HP-25 to the HP-33E, to the HP-15, to the HP-32 and HP-42, and finally to the HP-33S.
This part of the site has some of Dr. Bill Hazelton's collection of calculator programs. They are usually in a PDF file and can be downloaded to you computer. They do need to be entered manually into the calculator. For surveyors and engineers, the HP-33S and HP-35S can be taken into the various NCEES examinations, but the other HP calculators are not permitted at this time.
The programs are mostly surveying and geomatics oriented.
Enjoy, and we hope you find them useful.