HP HP-28S - Page 305

Nevertheless, using the RPN stack for simple arithmetic is most likely
the biggest stumbling block for algebraic calculator users trying to
learn to use RPN calculators. RPN is very efficient, but it does require
you mentally to rearrange an expression before you can calculate re-
sults. But
the HP-28S's capability of interpreting algebraic expressions
without translation should make the transition from algebraic calcu-
lator use more straightforward than has been possible on previous
RPN calculators. The four-line display can also help to take away
some of the mystery of the stack, by showing you the contents of up
to four levels at a time.
For
the purpose of evaluating algebraic expressions, the HP-28S is es-
sentially a Hdirect
formula entryH calculator. That is, to evaluate an
algebraic expression, all you have to do is precede it with a ~, key in
the expression in its algebraic form, including infix operators, prefix
functions,
and parentheses, and then press I EVAL I to see the result.
You
can use this method even for simple arithmetic:
~ OJ ~ [[] G []] I EVAL I returns o.
Except for the preceding~, these are the same keystrokes you would
use on a simple algebraic calculator, where you substitute I EVAL I for
G·
"
Note
304
Don't confuse the HP-28S G key with that found on alge-
braic calculators -
on the HP- 28S, G is used for the sole
purpose
of creating algebraic equations (described in
"ALGEBRA" in the Reference Manual).
C: Notes for Algebraic Calculator Users