HP HP-42S User Manual

7 Using the Solver
Unfortunately the HP-42S does not have an equation editor like that of the 33S. To use the solver and
numeric integration we must enter the equation in a program which must have a global name.
Let's suppose we want to solve the equation x
2
– 5x + 4 = 0 . We are going to enter it in a program.
For example:
01 LBL “FX” (“FX” is the global name of the program)
02 MVAR “X” (You find this in Solver menu. I will explain this later)
03 RCL “X”
04 X↑2
05 5
06 RCL “X”
07 ×
08 –
09 4
10 +
11 END
Well, as you can see we don't enter the equation f(x)=0 but just the function f(x). The MVAR function
tells the calculator what variables must appear in the solver menu. We suppose all variables are in the
memory so we use the RCL function.
Now we leave the program mode and we go to the Solver menu. What should appear is
Select Solve Program
followed by a menu of available Solver programs. Then in our case we select FX and we give a start
value, for example 8 and we press X to enter this value. Again we press X to calculate the correct
value of x which gives us X=4.
But this equation does not have only one solution. X=1 is also a solution. To get it we can enter 2 for
example for the start value.
If you want to solve numerically many equations of the form ax
2
+ bx + c = 0 you can write a program
such as
01 LBL “FX”
02 MVAR “A”
03 MVAR “B”
04 MVAR “C”
05 MVAR “X”
06 RCL “X”
07 X↑2
08 RCL “A”
09 ×
10 RCL “B”
11 RCL “X”
12 ×
13 +
14 RCL “C'
15 +
16 END

HP HP-42S Specifications

General

Model	HP-42S
Manufacturer	Hewlett-Packard
Release Year	1988
Display	LCD
Processor	Saturn
Programming	RPN
Special Features	Matrix operations, complex numbers
Category	Programmable Scientific Calculator
Dimensions	148 x 80 x 15 mm

Summary

2 Basic Operations

2.1 RPN Explanation

Explains Reverse Polish Notation (RPN) and its usage on the HP-42S calculator.

2.4 Training RPN with HP-42S

2.5 Understanding Menus

2.6 DISP Menu Functions

2.7 MODES Menu

Covers angle modes (DEG, RAD, GRAD) and coordinate systems (REC, POLAR).

2.8 The Stack

Explains the calculator's stack registers (X, Y, Z, T) and their behavior.

2.9 Key Usage Guide

Details the function of various keys like 1/x, LOG, LN, XEQ, STO, RCL, SIN, COS.

3 Memory Management

3.1 The CATALOG Menu

3.3 The CUSTOM Menu

5 Complex Numbers

5.1 Rectangular Coordinates

How to input and manipulate complex numbers in rectangular form.

5.2 Polar Coordinates

6 Programming

6.1 Basic Programming Concepts

Introduces fundamental programming concepts and syntax.

6.2 Managing Multiple Programs

6.3 Conditional Execution (X?0, X?Y)

Explains conditional execution (IF statements) in programming.

6.4 Real Program Examples

Practical examples of programs, including a prime checker.

7 Using the Solver

Solver Feature Guide

Guide to using the equation solver feature for numerical solutions.

8 Numeric Integration

Numeric Integration Guide

How to perform numerical integration of functions using the calculator.

9 Statistics

9.1 The CFIT Sub-menu

10 Matrices

Matrix Operations Overview

Covers matrix operations, creation, inversion, and determinants.

12 Flags

Calculator Flags Explained

14 Comprehensive Command List

HP-42S Command Reference

An alphabetical reference of all HP-42S functions and commands.