HP HP-28S User Manual

23
Evaluation
All calculator operations, from simple keyboard calculations to com-
plicated programs, involve evaluation.
Some examples:
•
When you key one or more objects into the command line and
press I ENTER I, the command line is translated into a program,
which is then evaluated.
•
When you press a key on the USER menu in Immediate entry
mode, the corresponding name is evaluated.
•
When you perform step-by-step differentiation, you press I EVAL I to
evaluate
the expression in level 1.
• When you use the Solver to find numerical solutions, the procedure
stored in the variable EQ is repeatedly evaluated.
It's easiest to
understand calculator operations in terms of delaying
evaluation
and causing evaluation. Although the term "delaying eval-
uation" is new,
the process is familiar: whenever you enter a quoted
name or an algebraic, the object's delimiters indicate that you want to
delay evaluation
of the object-that you want the object to go on the
stack.
Delayed
evaluation is the basis for programming on any computing
device, since otherwise a program would execute as soon as you
wrote it. The HP-28S extends the concept in a uniform way to allow
symbolic operations-you can use names and algebraics as data for
symbolic calculations. For example, you choose
when, if ever, you
want to evaluate an expression. You can differentiate it, symbolically
solve it, make substitutions for variables in it, and so on. Of course,
you
can also calculate its numerical value.
198 23: Evaluation
I

HP HP-28S Specifications

General

Brand	HP
Model	HP-28S
Category	Calculator
Language	English