The TI-83 Plus is an older model of programmable scientific calculator. This is the 4th one we each use. I am an electrical engineer, and my wife is working in medical nutrition at the clinical level.
We each both need a practical type of calculator for being able to quickly solve equations we each commonly use. Her applications are in the bio-medical field, and mine is with solving electrical engineering problems. We each have over 20 different formulas written in to our calculator. We also keep a calculator on hand as a spare in case one of these fail.
I was able to write the software coding based on required formulas and save it to this model of calculator. We have the original detailed instruction books for this calculator giving examples of the coding and process about how to write software in to this model type. It is fairly involved, but works out very well. This calculator model is a very advanced type for its size and gets the equations easily and quickly solved. It is much more convenient for portability than using Excel or some other type of math software on a laptop.
We have the TI calculator management software installed in our computers, and can back up the calculator's programs to the computer's data drive. We have been using this model of calculator since it came out and being used to it and very proficient with this model, makes our preference is to not change the model. There is a newer equivalent version with advancements for the display and etc.
We have been using this model of calculator sometimes every day since 1998 when they came out. Over the years with use they have eventually failed. Sometimes the calculator may be dropped, and over time with use there are wear factors involved. With near daily use and for at least an hour or more per day we are getting about 4 to 6 years of use from each calculator. This is terrific.
The memory battery lasts about 3 years average in these. This is not difficult to change. The main batteries last about 6 months to 1 year with daily use. There is a procedure to allow the memory battery to be changed without losing the programs stored in calculator.
With the data transfer cable that comes with the calculator it is possible to back up the calculator's programming and variables to another one like it. There is also the silver USB type interconnect cable that allows this calculator model to be backed up to a computer using the TI calculator management software.