The Operator of my Pocket Calculator

I have to say, it's a little unsettling, having to study for finals at my advanced age. The first was today, and then two more tomorrow; and I did two take-home finals, so it's been a pretty interesting week.

Today's involved a lot of linear algebra, basically finding e^At, working with Laplace transforms and their inverses, Smith McMillan canonical forms for polynomial matrices, etc. And through all of this, I would have been absolutely sunk without my TI-89.

This brings back memories. Back in high school, I was the proud owner of what, at the time, was probably the most sophisticated hand-calculator made, the HP-41C. I could go on and on about it: it had some alphanumeric capability, it had a fair amount of memory for programs (basically sequences of simple instructions that worked with data on the stack), etc. You could add plug-in memory modules, and a variety of other little gizmos (including a bar-code reader). It certainly threw my first serious calculator, which I got when I was 13 or so, into the shade. (That was an HP-33C. It was programmable too, and I spent a lot of afternoons making it do little mathematical things. You are probably not wondering whether I was "cool" in high school, are you? Plus, I've dated myself. When I got the 33C they had just been released).

Needless to say, I was an HP snob; I was comfortable with RPN from day 1 and felt better-equipped than those who were forced to suffer with lesser calculators, typically the TI.

Well, times change. It seems to me that HP is basically out of the advanced calculator market. Yes, there's the HP-48, but there is no comparison to the TI: the TI pwns in all categories. Determinant of a matrix with symbolic entries? Check. Partial-fractions expansion of a rational function? Check. How about taking the limit of a matrix with symbolic entries? Unbelievably, yes: one step in constructing a minimal realization for a dynamic system involves evaluating lim_s→λ(s-λ)H(s) where H is a polynomial-matrix-valued function of s. And the TI can do it. If HP ever makes a calculator that can perform like that, I'll give it a try, for old time's sake; HP got me through high school and college.

I didn't like buying the TI, and there are a few things about it that irritate me, but over this last quarter I've come mightily to appreciate it!