HP-15c: Why so popular?

[rprosperi]

@Valentin - Bravo, an excellent list of advantages of the 15C over the 41C, all in one place! None of these are news to me, but I am certain I could not have created a list that complete off the top of my head. One very minor nit is the 15C does in fact have a few non-immediate commands for Matrix and comparisons, however they were conveniently documented on the permanent label on the back.

@Max - While the TI-59 (and 58/58C) had optional ROM modules supplying many of the built-in 15C capabilities (as well as many not found in the 15C), for a fair comparison these should not be included. Matrices, Complex, Solver, etc. are key differences where modules were needed and adding the cost for some of these changes the cost advantage considerably. But, yes, these machines were indeed excellent and pushed HP more than any other model at any time IMHO.