Published on by JGD
# My configuration for the HP41CL

I have just loaded in my tall keys hp41c the latest modules that I didn’t have, and I have refreshed the key assigns, that were quite old. I have made a mix of work related needs, curiosity programs and help to my children’s school chores.

Work related: most of my day job relates to financial control. It involves analysis of production investments, business plans, etc. These are often discussed in meetings, and then you need to be really fast to give a solution - an it’s quite difficult to have an open computer during the meeting, lest the colleagues are led to believe that you’re emailing while they’re discussing! So the logical choice is to use a calculator.

While you can imagine that I have all of them, my go-to calculators are the hp15c (that I have equipped with time value of money, net present value, internal return rate, percentage of total value, days between two dates and weighted averages (we sell tons of different products at different margins, so a weigthed average calculation, based on the statistical values registered, makes a lot of sense). All of this consumes around 210 steps of memory, leaving enough room to solve a 3*3 equation system (that I may have to solve together with my children)

In addition, the 15c I have in the jacket pocket, so if I have to enter in a meeting unwarned, then I’m prepared.

But if I’m prepared, then I take the hp41cl. To begin with, its user keyboard allows me to put many more programs. I have loaded the YFZN and PowerCL in lower and upper port 1; the advantage module in Port 2, and Sandmath 3x3 in module 3. I have a time module and an infrarred printer driver plugged in but not using the corresponding logical ports (I think that they use port 6 and 7, but I may be wrong)

For IRR and NPV I use my own programs instead of the many you can find in either the advantage of diverse financial pacs. As I know the location of the registers used, then I can put data in them “offline”, prior to running the program, and dispense with cumbersome data entry procedures.

I also have assigned to specific keys DATE+, DDAYS, and a very short utility but very used in project management: what calendar day is x days from now, which implies asking today’s date, and then DATE+ with the content of the X register.

I have also assigned the weighted average, and the %CH and %T keys (this later one is easy to program but I took it from the Sandmath 3x3 module)

And then, there come the ones that can be used for my children. Sandmath includes a number of interesting routines to deal with fractions. One is D>F, which turns a decimal number into a fraction. I seem to remember that which approximation it takes is based on the number of decimal places set for the screen. The function gives an alpha return with the fraction (for example, pi is converted to and shown as 333/106), while the fraction components are written to Y and X respectively.

Then I have also put on the shifted keys for the 4 arithmetic calculations F-, F+, F* and F/. These use the fractions represented by T/Z and Y/X to perform the arithmetic, and then leave the results as Y/X, as well as showing the result in the alpha register

And finally, I use the XYZAlarm to keep reminders. This is just for the sake of using it - any smartphone is better than the 41CL for this task.

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