HP 15c Collector's Edition User Manual

116 Section 10: The Index Register and Loop Control
I and e
For the purpose of loop control, the integer portion (the counter value) of
the stored control number can be up to five digits long (nnnnn.xxxyy).
The counter value (nnnnn) is zero if not specified otherwise.
xxx, in the decimal portion of the control number, must be specified as a
three-digit number. (For example, “5” must be “005”.) xxx is zero if not
specified otherwise. Whenever I or e is encountered, nnnnn is
compared internally to xxx, which represents the end level for
incrementing or decrementing.
yy must be specified as a two-digit number. yy cannot be zero, so if left
(or specified) as 00, the value for yy defaults to 1. The value nnnnn is
altered by the amount of yy each time the loop runs through I or
e. Both yy and xxx are reference values, which do not change with
loop execution.
Indirect Display Control
While you can use the Index register to format the display manually (that
is, from the keyboard), this function is most commonly used in
programming. This capability is especially valuable for the f function,
for which accuracy can be stipulated by specifying the number of digits to
be displayed (as described in Section 14).
There are, as usual, certain display limitations to keep in mind. Recall that
any display format function merely alters the number of decimal places
to which the display is rounded. In its memory, the calculator always
retains a number in scientific notation as a 10-digit mantissa with a two-
digit exponent.
The integer portion of the number in the Index register specifies the
number of decimal places to which the display is rounded. A number less
than zero defaults to zero (zero decimal places displayed in • format),
while a number greater than 9 defaults to 9 (9 decimal places displayed
in •).
*
*
Note that in i and ^ format modes, the maximum display is a seven-digit
mantissa with a two-digit exponent. However, a format number greater than six (and
less than or equal to nine) will alter the decimal place at which rounding occurs. (Refer
to pages 58–59.)

HP 15c Collector's Edition Specifications

General

Model	HP 15c Collector's Edition
Category	Calculator
Type	Scientific
Power Source	Battery
Manufacturer	HP
Display	LCD
Functions	complex numbers, matrix operations

Summary

Introduction

This Handbook

Outlines the structure of the manual, detailing its parts and how to use it for learning.

The HP Community

Discusses user groups and websites for HP calculator enthusiasts and information sharing.

Part I: HP 15c Fundamentals

Section 1: Getting Started

Covers basic operations like powering on, keyboard layout, and primary/alternate functions.

Section 2: Numeric Functions

Explains essential numeric operations including logs, trig, powers, and conversions.

Section 3: The Automatic Memory Stack, LAST X, and Data Storage

Details the RPN stack, LAST X register, and data storage operations.

Part II: HP 15c Programming

Section 6: Programming Basics

Introduces core programming concepts: creating, loading, running programs, and memory.

Section 8: Program Branching and Controls

Covers controlling program flow using branching, loops, and conditional tests.

Part III: HP 15c Advanced Functions

Section 11: Calculating With Complex Numbers

Covers entering, manipulating, and performing calculations with complex numbers.

Section 12: Calculating With Matrices

Explains matrix operations, including dimensioning, element access, and calculations.

Section 13: Finding the Roots of an Equation

Details using the SOLVE function for numerical root finding and equation solving.

Section 14: Numerical Integration

Explains how to perform numerical integration using the ∫f(x)dx key and subroutines.

Appendix A: Error Conditions

Error 8: No Root

Explains the error when the SOLVE function cannot find a root.

Error 0: Improper Mathematics Operation

Lists and explains errors related to mathematical operations and illegal arguments.

Appendix D: A Detailed Look at SOLVE

How SOLVE Works

Explains the numerical technique and logic behind the SOLVE algorithm.

Finding Several Roots

Discusses methods for finding multiple roots of an equation using the SOLVE function.