Re: 15C solver/33S equation editor Message #9 Posted by Karl Schneider on 3 Apr 2006, 9:32 p.m., in response to message #1 by Hal
Hal --
Lots of good info from Thomas, Luiz, Bill, and Valentin to your queries. I'll try to summarize it:
HP-15C solver:
The SOLVE and INTEG functions on the HP-15C were taken directly from those implemented on the HP-34C. These functions load the stack with the current value of the variable to be solved or integrated, as a convenience to the user. Of course the variable can also be saved to a numbered storage register, and taken directly from there in the user-defined function. This technique, using the indirect register, is the basis for using this implementation of SOLVE and INTEG adroitly with multiple-input, single-output (MISO) functions.
The HP-15C requires 5 user-allocatable "common pool" registers to run SOLVE (and 23 to run INTEG, or to run INTEG and SOLVE together). The HP-34C has the same memory requirements for SOLVE and INTEG, but it uses non-allocatable registers that are hidden from the user and cannot be used for data storage or programming.
My discussion of the implementation of SOLVE and INTEG, along with the MISO-function technique, was developed into Article #556 posted in the MoHPC Articles Forum.
HP-33S Equation Editor:
Yes, the lack of full "insert/delete" mode of the HP-33S equation editor is annoying, but it stems from display capabilities and cursor-movement keys that are limited. The equation functionality was originally implemented in the algebraic HP-22S, and transferred to the HP-32SII, which replaced the HP-32S. All the functionality of the HP-32SII was ported to the HP-33, but not much was added. Also, none of these calc's offer the HP-17B/27S/42S high-resolution dot-matrix display that allows softkey menu labels to be displayed on the keyboard.
Bill made a very good point that the equation editor on the HP-33S should be treated as a "bonus", not as a core capability. Long equations can be hard to read, decipher, and edit. Furthermore, any supported capability -- including branching by conditional tests and loops -- can be used in a keystroke program, but not necessarily in an equation. Also, SOLVE and INTEG run faster when using a keystroke program instead of an equation.
-- KS
Edited: 4 Apr 2006, 3:25 a.m.
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