I have had an FX850P Casio calculator/computer for many years. I don't know why they never took off. It runs basic, does macros, and allows you to write and store formulas in a library for recall as a calculator function later. You can write long formulas with variables and enter the data as you make calculations. Although much of what it does is now handled by a laptop, it is smaller than many scientific calculators today. In addition to all of the above it also has a function library built in that will make calculations such as quadratic equations, Bessel functions, LaPlace transforms, conversions of any unit between standards, calculate areas, do statistics and it even has a periodic table built in. I have an interface for it that will store all saved memories to cassette tape and talks to a printer. You can even stack formulas so that you enter data in one, it makes the calculations and continues to enter the answers into the next formula. It was sold for a short time through Radio Shack under their own name but I bought mine under the Casio brand from an outlet here in Chicago.
Here is a spec sheet...
http://en.wikipedia.org/wiki/Casio_FX-850P
BTW I have formulas for speaker system design and layout, dB to voltage conversions, resonant circuits and antenna designs loaded in as well a program for calculating billing info (hours worked, miles traveled, expenses, parts, totals).