Hi, Joan;

I believe the HP11C is the pre-15C, although many HP11C owners do not agree with. The HP15C has everything the HP11C has plus matrices, complex math, numerical solve and integrate. To handle most of these features, it has 448 bytes RAM user memory, that allow the user to compute the inverse of an 8X8 real matrix or a 4X4 complex matrix in one key: [1/x] (after input all data, of course). And the eight conditional tests were expanded to ten but had their key inscriptions reduced to three, leaving five places for the new features.

The HP42S ia a lot more than this. I have two HP15C and two HP42S (one of them I upgraded to 32KRAM, thanks to Randy's final guidance... I'll always mention it) and I also have an HP11C. All of them have their applicability and there are things that the HP11C can do and I use it. If I am interested in tdevelopiong a program and I want to know if it fits in an HP11C I do not need to make post considerations after loading it in an HP15C to be sure if it fits or not. I simply load it in the HP11C and run it.

What for? Sometimes for fun, sometimes as a request. I have done a lot of programming when I was at the university, in a time Voyagers, Spices, HP41 and TI58/59 used to share the space with Sharp and Casio pocket computers.

What a time, what a time...

Now we have 16's and 17's crackers breaking NASA and CIA net passwords... for fun.

What a time, what a time...

Cheers.

Luiz C. Vieira - Brazil