HP HP-28S User Manual

For example, the user function COT (from chapter 5) was written:
Here the local-variable structure stores one argument in a local vari-
able
}:: (satisfying the first requirement) and evaluates the expression
, I
t,fI..! 0:: TAt·l 0:: ::<::0 ::0 ' (satisfying the second requirement). The user func-
tion O-C (from chapter 14) included a program rather than an
expression but, since the program returned exactly one result, O-C
also satisfied the second requirement.
These requirements apply only to user functions. More generally, local
variables are
used as a substitute for stack manipulations. The follow-
ing example returns the sum and difference of two numbers. Since it
returns two results, it can't be a user function.
« ~ x y « x y + x y - » »
For more examples, see the programs in chapter 28. They use local-
variable
structures more often to avoid stack manipulations than to
create
user functions.
Conditional Structures
Conditional structures enable a program to test a specified condition
and make a decision based on the result of the test. This section first
gives
an example of a conditional structure. It uses that example to
discuss
program structures in general, and then it describes other
types of conditional structures.
Suppose you're writing a program that uses the variable x, and you
want to calculate (sin x)jx. A problem arises because the quotient is
undefined when x = O. The following example returns (sin x)jx if
x =1= 0, or returns 1 if x = O.
IF X 0 ~ THEN X SIN X / ELSE 1 END
26: Program Structures 223

HP HP-28S Specifications

General

Introduced	1988
Memory	32 KB
Number of Digits	12
Type	Scientific Calculator
Manufacturer	Hewlett-Packard (HP)
Display	LCD
Processor	Saturn
Programming	RPL

Summary

HP-28S Advanced Scientific Calculator Owner's Manual

Part 1: Fundamentals

Introduces basic operations, calculator features, and core concepts.

Getting Started

Covers initial setup, basic operations, and calculator overview.

Doing Arithmetic

Explains methods for performing calculations using stack and expressions.

Part 2: Summary of Calculator Features

Objects

Describes fundamental data types, symbolic operations, and programming elements.

The Command Line

Explains input methods, cursor control, and command entry.

The Stack

Reviews stack concepts and commands for manipulating objects.

Part 3: Programming

Program Structures

Covers conditional logic, loops, and error handling in programs.

Conditional Structures

Explains testing conditions and making decisions within programs.

Definite Loop Structures

Details structures for executing code a specific number of times.

Appendixes & Indexes

Appendix A: Assistance, Batteries, and Service

Provides troubleshooting, battery info, and service details.

Answers to Common Questions

Addresses frequent user queries and common calculator issues.

Appendix B: Notes for HP RPN Calculator Users

Highlights differences for users familiar with RPN calculators.

Appendix D: Menu Map

Lists commands by menu, with descriptions and page references.

Contacting Hewlett-Packard