The HP-55 Enigma

[Matt Agajanian]

Hi all.

I’m trying to make sense of the why, how, where of the HP-55. Armed with two conditional tests, no subroutines, 50 partially merged program steps, what was the intended objective of the 55?

The way I see it—with its function set, it seems a stronger scientific calculator than a programmable.

So, please enlighten me.

Thanks

[Steve Simpkin]

Well despite its limited programming model, it did get you an HP programmable calculator for about the same price as a HP-45 and half the price of a HP-65. It also had a cool (and accurate) timer function and a lot metric conversions which would be very useful when the U.S. changed to the Metric system, which we were assured would only be a matter of days away.

Of course 7 months later the HP-25 came out at half the price of the HP-55. It had 49 fully merged steps and more tests but fewer memories, no timer and no metric conversions. The price of the HP-55 was dropped to $335 about 2 months later.

[Matt Agajanian]

Cool! Kinda makes me appreciate the 55 programs here in the software forums. Yeah. I remember those days. America on metrics—now just a dream.

[toml_12953]

(08-04-2021 05:09 AM)Matt Agajanian Wrote:  Cool! Kinda makes me appreciate the 55 programs here in the software forums. Yeah. I remember those days. America on metrics—now just a dream.

We actually had KPH signs along major highways for a while. Ah, the good old days.

[mfleming]

(08-04-2021 12:31 PM)toml_12953 Wrote:  

(08-04-2021 05:09 AM)Matt Agajanian Wrote:  Cool! Kinda makes me appreciate the 55 programs here in the software forums. Yeah. I remember those days. America on metrics—now just a dream.

We actually had KPH signs along major highways for a while. Ah, the good old days.

Those signs were dropped no doubt because the lettering was reduced to fit the dual markings in the same size sign area, making them difficult to read at distance and speed. I was glad when they went away. But show me something else in the USA these days that isn't dual marked in English/Metric measurements. Other things have gone full metric - can you name one?

[KeithB]

There are still a few kilometer markers on I40 near Needles.

For reasons I have never been able to fathom, in engineering we use US units for everything else *except* temperature which is always in deg C. It must predate me, and I have been in the industry since the early 80's.

[Valentin Albillo]

(08-04-2021 03:07 PM)KeithB Wrote:  For reasons I have never been able to fathom, in engineering we use US units for everything else *except* temperature which is always in deg C.

And this is what happens when Murphy takes the chance.

V.

[Dave Shaffer]

(08-04-2021 02:40 PM)mfleming Wrote:  But show me something else in the USA these days that isn't dual marked in English/Metric measurements.* Other things have gone full metric - can you name one?

Wine bottles!

* I wish writers/editors knew something about significant figures. NASA, say, will report that some asteroid is some 100 meters in size (so one significant figure - at best), and that will appear as 328 feet in some article!

[Namir]

(08-04-2021 04:14 AM)Matt Agajanian Wrote:  Hi all.

I’m trying to make sense of the why, how, where of the HP-55. Armed with two conditional tests, no subroutines, 50 partially merged program steps, what was the intended objective of the 55?

The way I see it—with its function set, it seems a stronger scientific calculator than a programmable.

So, please enlighten me.

Thanks

The HP-55 was my first HP calculator. I used the programming to transform variables for the linear regression. I was also able to push the machine to limit to calculate summation series. As an engineering student I did use the timer in performing experiments in my personal lab (at home) and indeed benefited from the unit conversion features.

My second HP calculator was the hP-67 with its relatively advanced programming features (more steps and merged ones at that, a bit more memory, labels, subroutines, indirect addressing, and program/data I/O on magnetic cards).

Namir

[Gamo]

Another programming functions that HP-55 doesn't have is the [FRAC] and [INT]

So I found that HP use special program algorithm to do [FRAC] and [INT] in the

HP-55 Applications Book

I took part of this program and test on HP-12C here

https://www.hpmuseum.org/forum/thread-14...=%2812C%29

gamo

[Thomas Okken]

(08-04-2021 10:42 PM)Dave Shaffer Wrote:  I wish writers/editors knew something about significant figures. NASA, say, will report that some asteroid is some 100 meters in size (so one significant figure - at best) [...]

The way I learned it, 100 has 3 significant digits. If you wanted to express that number as having only 1 significant digit, you'd write 1x10^2.