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My HP-25 and being able to program!

Posted by Michael Brown on 16 Dec 2004, 6:00 p.m.

In the early 1970s, no one had calculators. Instead, at my high school, we had a physics class that had spent considerable time teaching us how to use the slide rule. One friend had a Bomar calculator but all it did was the four basic functions and it didnít have scientific notation. It was useless so we all jokingly referred to our friendís calculator as the bomar brain.

Then the rich kid got an HP-35. We couldnít believe what it could do, it was a serious calculator. It looked like something the people at NASA would use. But it was no use thinking about it, I was only in high school and it cost over $400! So off to college I went with my slide rule.

Actually, I wish kids today had to use the slide rule because it helps the user exercise their brain in knowing the approximate answer before the actual numbers are realized. So many people today, treat the calculator as a black box and they will accept almost any kind of answer from it. Even when it is ridiculously wrong.

I went through my first year of college keeping track of the decimal point and using log tables. Then they came. I saw the new inexpensive HP calculators at the college store, the HP-21 and the HP-25. I knew that I should buy the 21, I couldnít afford anything better. But every time I would start thinking that way, I would see the 25. It was real cool, too good to pass up. It did so many neat things. It was more than I could afford but I bought the HP-25 anyway. I don't know what I did without, but it was the best thing I could have done! I learned so much from that little calculator.

Two books were in the box with my new HP-25. One of the new pictures of the Earth was on the cover of both books in sharp detail. You must realize that I was of the generation that grew up with the space program. I watched John Glenn make his trip around the world when I was in first grade, actually all school activities stopped that day and we spent the whole day sitting on the floor of the gym watching the historic event on a B/W TV set. Every time a Mercury, Gemini, or a Apollo Moon rocket would blast off, I would be glued to the TV set. So when I saw the NASA photos on the cover of the books, it made me feel like I had arrived! I was working in the right direction. Inside, these books told me how great RPN was and that it was extremely easy to program the HP-25. In fact, it said that what I had in my hands was impossible only a few short years ago, without spending several thousand dollars for a desktop calculator. ďThe HP-25 puts programming into the hands of the individual!Ē

I literally read these books all weekend while I played with my new calculator. Before the weekend was over, I knew all the functions on the calculator and I also found that I could program!! I didnít fully realize what I had done until later when I started to learn BASIC programing, I found that I already knew how to program in BASIC! Things were just in a different format but it was the same concept. Fantastic!

I was on top of the world, that is until the HP-25C came out. Well anyway.

In spite of the fact that I now had a calculator, I still needed to take my slide rule to exams. The rule was: Only when everyone had a calculator could we all use our own calculator. When just one person didnít have one, then we would all have to use our slide rule. What a pain! You can imagine the groans in the room just before the exam, when it was found out that we would have to use our slide rules instead of our new calculators!

The neat thing about the HP-25 is itís ease of use. It is so easy to use. When we went into a science lab, most of the time, we had to make graphs by hand, right in lab time. The HP-25 was perfect for that. I would push the top switch to program and start pressing the keystrokes of the calculations we needed to do and that was that. Pushing the switch back to run and pressing gto 00, I was then able to start adding points to the graph.

When ever I needed to do a linear regression, I would punch in a short program that I wrote. My calculator did not have continuous memory so what I needed was a small program I could punch in every time I wanted to do a linear regression. HP had a fancy program in their programing book, but what I needed was something fast to key in. I think it was 11 or 12 steps with just the basic formulas needed for the process. It was such a short program that I would have it in memory in just a few seconds. It was extremely easy.

One time, in a lab something funny happened. I was in a lab class for Laboratory Technicians doing a chemistry test for some parameter. We collected our data than I brought out my calculator. I saw the calculations that we needed to do and I quickly put it in the program memory of the HP-25 and started to work on the answers. Almost immediately, the teacher came in with a new toy. He had a circular slide rule that he thought was pretty good. Most were pretty slow with their calculators and so our teacher challenged us to a race. He said he could get the answer faster on his slide rule than we could on our calculators. I said OK, Iíll try.

So, we were off. He was sliding things on his slide rule and I was punching the unknown value into my HP-25. Then I pressed the R/S button and away it went. As the red LEDís started flashing, I started to think, boy this thing is slow. Come on! Come on! Then out it came and I announced the answer. He looked up startled. I didnít tell him or anyone that I had programed my calculator before hand, but somehow, I have never felt guilty. Boy was that fun!

Years later, as a Chemistry Professor, teaching general chemistry, I saw something that really amazed me. I had quite a number of engineering students and they all had their new HP-48SXís in the room. (This is just a few years ago.) We were doing an experiment, and the computers were down for some reason. So I commented that maybe they could use their calculators to write a small program that would allow them to do the repetitive calculations easily and then they could do a linear regression which is an already built in function. They looked back at me with a blank stare. They just could not do it.

The HP-48 was so complicated that they were just trying to get a handle on how to use it period! They had not even gotten to the point where they could tackle the prospect of programing it. Nor were they clear on how to conduct a linear regression using the HP-48.

So because of its complexity, my students were not able to program nor do the simple kinds of things that I did with the HP-25. When I was in college, being able to program the HP-25 in class was the major advantage I had, especially when I went through my heavy science and math classes.

I look back to that time with fond memories when HP calculators were more simple to operate, when being able to program was a teaching process in of itself. I was able to write quick programs just when I needed them, to solve all sorts of problems that I ran into throughout the day. It became a daily routine because it was so simple to use. It was truly a great learning experience in of itself!

What my general chemistry students used their HP-48 calculators for, was to do the simple calculations that the HP-42 or HP-32 (The cheeper alternates of that day) is capable of doing. It may be that they were able to use some of the graphic functions to good use. But of course, the p.c. is so common place and high powered that I am sure that it would have been the tool of choice. But of course, the HP-48 looks cool and they could play the games that they downloaded from various sources.

When I was in graduate school, I had bought an HP-34C. It was also a great little calculator but early on, it had developed some real problems and I eventually threw it out (can you imagine). Now after reading the little post by norm ďHP-34C BETTER THAN S*Xď and other posts on how to repair these calculators, I now wonder if maybe I may try to get an HP-34C for myself again. Iím getting tired of my newer calculators (HP-42 and HP-48SX) and the menus.

Edited: 22 Dec 2004, 11:43 a.m.

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