HP-65 Diagnostic Programs

The HP-65 calculator came with a “Standard Pac” of programs. That was a set of ready made solutions for some common problems. The idea was probably: if the calculator is programmable, it ought to come with some programs to show that off. It also effectively provided training material that created a whole lot of new programmers. It was a very good idea in many ways.

The argument has been made that these were published without copyright notices and in an era where copyright protection required authors to include notices. I’m not a lawyer and I’m making no claims one way or the other. The programs in the HP released “Pac”s were written by HP.

As with most software these days, you should assess its suitability for your needs. The disclaimer applies to any programs on this site written in calculator languages, as well as normal computer languages. Please don’t blame HP if I’ve typed something incorrectly or if it was something they fixed long ago and I missed the fix.

Calculator programs on this site are simply a convenience to save you typing them in by hand.


The Standard Pac came with two “Diagnostic Program”s. These checked out the functioning of the calculator and reported okay or failure. I have even seen an internal servicing bulletin at one stage where the first step taken by HP technicians was to run the diagnostic programs.

The idea behind the programs is fairly standard these days: do something, get a result, compare that to the expected result, announce success or failure. In 100 steps or less, it isn’t always as clear as that sounds but they do follow that principle.

You can see the programs at:

To use either program, load it, press RTN to ensure you are at step “00 00”, and press the [R/S] key.

(To load a program into my emulator, tap the display at the top of the emulator to bring up the menu, choose “Program”, tap in the text box, select all of the existing text and then paste the program over the top. Click “Back” twice and you’ll see a program card in the slot.)

Diagnostic 1

A successful result is all 8s in the display and minuses shown for the number and exponent. This actually tests the 7 segment display chips (and the components that run them).

If the program gets an unexpected result, it stops and shows one of the following:
0 g x!=y
1 f TF1 with flag clear
2 f TF2 with flag clear
3 g x<=y
4 f-1 TF1 with flag set
5 f-1 TF2 with flag set
6 g x=y
7 f-1 SF1
8 f-1 SF2
9 g x>y
-1 DSZ

Diagnostic 2

This has the same successful output.

The process for errors is a lot more complex as the user needs to SST through the program and manually compare results with expected values listed in the manual for the Pac.

Given a lot more gets tested in this program and our 100 step limit, the need for more human involvement this time isn’t surprising.

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