A collection of photos of my favourite calculating devices
and some programs written for them.
Sinclair Scientific calculator

I bought this as a kit in 1974/1975. Amazingly it worked first time and overnight replaced my slide rules for calculations. It was slow and accurate to only 2 decimal places (Sinclair claimed 3 decimal places!) and had a limited set of scientific functions. It also used the Reverse Polish Notation (RPN) system of calculation. This was in use every day until 1977 when it stopped working.

The example shown here was obtained from eBay in 2019.

A web-based emulation of this calculator can be found here.

Texas Instruments SR-56

The SR-56 was an amazing calculator which I bought in 1977. Not only did it have a very good set of scientific functions built in but also it was programmable. One could enter programs of up to 100 steps. The programming model included conditionals and subroutines. This was my workhorse calculator until about 2015.
Texas Instruments TI-59

At the time this came out it represented the pinnacle of TI's programmable calculators. With up to 960 program steps and a built in magnetic card reader/writer it was a hugely powerful calculator. The calculator can also accept a number of ROM modules which can change the function of the calculator.

I have managed to collect most of the ROM modules and only lack the Electrical Engineering, RPN and Agriculture ones.

This was bought in 2016 along with a PC-100C printer cradle.

Hewlett Packard HP-41CX

The ultimate development of the HP-41C. As well as having the expanded memory size, this variant includes a real-time clock and an X-memory system which, among other things, can be used as a simple filing system for saving programs. The HP-41CX uses RPN.

My HP-41CX was purchased in 2012.

There are many peripherals available for the calculator. They plug into ports at the top. These include ROM modules, which expand the capabilities of the calculator, a magnetic card reader/writer for program storage, a printer and a bar code reader for inputting programs saved as bar codes.

Hewlett Packard HP-12C

One of my latest acquisitions bought in 2018, this is a financial calculator. It uses RPN and is programmable.
Hewlett Packard HP-16C

Bought in 2017 this is one of my real favourites.

It is a computer programmer's calculator working in binary, octal, denary and hexadecimal. Also programmable, it can mimic many machine code operations. It is used regularly when working with 6502 machine code for debugging and testing.

Texas Instruments TI-66

This has a similar programming model to the TI-59. It is a LCD calculator and is non-volatile. It is also incredibly slow at running programs. I quite like it though and use it for day to day calculations.
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