I did a lot of programming on the IBM mainframe for many of my university courses and just to see what it could do. My next major involvement with computers happened by a fortunate set of circumstances that landed me a summer job at the Ministry of the Environment for the Government of Ontario working in the waste water department. It was a great summer job and if anyone is reading this from that time I really appreciated it. When I interviewed for the job I was asked whether I had ever programmed an HP computer. I replied that I had an HP-25 calculator and I programmed it a lot so I go the job! I’m not sure if they realized the difference between my calculator and the HP-9825 computer that they hired me to use, but it was no problem to learn since it used a form of basic written by HP called HPL.
The HP-9825 is quite a rare computer and it was very expensive for the time. The HP-9825 had an integrated keyboard and processor unit with a one line display so you could see what you were typing. You could also print out your programs on an HP daisy wheel printer so it was not a problem to debug your work instead of using the built in thermal printer. HPL is a form of basic and very easy to use and soon I was consulting on programs in other departments as programming was very new at that time. One interesting application for the HP-9825 was that it could dock with a gas chromatograph and become the processing unit for it. Output was on an attached HP plotter. I have looked for this configuration, but cannot find it. I would use the computer on the gas chromatograph every once in a while if the other ones were occupied.
My main assignment at the time was to develop a program to analyze plug flow in sewers to ensure that there were no side flows or major breaks in the line. To test a sewer a manhole was opened and dye injected into the water at a constant rate for a fixed amount of time, say one minute. A mile away a sampling team would take samples of the water and record the levels of the dye as it came past. In an ideal case, the flow concentration would be constant and last one minute. The time between the injection of dye and the first sample was used to calculate the flow speed and volume flow rate. In real life, there were changes in direction and cross section of the channel that allowed some of the dye to stray from the main stream, recirculate in eddies and delay the arrival of the dye. The typical dye concentration curve had a large spike in concentration with a logarithmic decay. The program I wrote analyzed the log slope of the decay and totaled up the flow to see how much of the dye could be accounted for. This was based on work done by Professor Leutheuzer would be my fluid mechanics professor the following year! Today this would be a simple Excel spreadsheet, but on the HP-9825 it had to be programmed.
Another assignment was to make a contour line plot of concentrations of water contaminants based on measurements from a fixed grid of bore holes. Every month a team would go into the field and take water samples and analyze the concentrations in the lab. I programmed in the building outlines, the names of the sampling locations, and the levels at each location to make a complete plot. The HP-9825 had a contour plotting routine that would take the data and plot the contour lines. The output was done on a pen plotter which used (4) felt pens to draw what your programmed.
The pen plotter had HPL functions to plot axes if you were making graphs and you could move and set a zero point to help with this task. Plotters were the only way to get graphic output and were limited to lines. It could fill in images with varying levels of reliability depending on whether you were using paper, transparency film and whether the pen was new or old.
The one line display was a little awkward, but otherwise the computer was really well built and well designed – just like the calculators. This is a computer that only institutions could afford as the original selling price in 1976 was $5900 (around $20,000 today) The tape storage drive worked well and was compact, but it was a bit slow. These tapes were the forerunner of tape backup drives that are now in common use.
I got to go on several field trips while I was at the Ministry of the Environment inspecting sewers, helping with tests and even a visit to a monitoring station in Muskoka. It was great summer.
This is end of Part 2. In Part 3 I start to work on my undergraduate thesis.