Notes
for Algebraic
Calculator Users
c
Many
calculators,
including
the
great majority
of
simple, "four-func-
tion" calculators,
use
variations
of
the
algebraic
calculator interface.
The
name
derives from
the
feature
that
the
keystroke sequences
used
for simple calculations closely parallel
the
way
in
which
the
calcula-
tion is specified in algebraic expressions "on paper."
That
is, to
evaluate 1
+ 2 - 3, you press
OJ
G
[l]
G
rn
G·
This interface works nicely for expressions containing
numbers
and
operators-functions like +,
-,
x,
and
/
that
are
written
in
infix
notation
between
their arguments. More sophisticated calculators al-
low you to
enter
parentheses
to specify precedence (the
order
of
operations). However,
the
introduction
of
prefix functions, like SIN,
LOG,
and
so on, leads to
two
different
variations:
•
Ordinary
algebraic calculators use a
combination
of
styles-infix
operators
remain
infix,
but
prefix functions are
entered
in
a postfix
style (like
RPN
calculators). For example, 1 + SIN(23) is
entered
as
OJ
G
[l]
rn
[]!ill
G·
This
approach
has
the
advantages
of
being
able to
show
intermediate
results,
and
of
preserving single-key
evaluations
of
prefix functions
(that
is,
without
parentheses),
but
the
disadvantage
of
losing
the
correspondence
with
ordinary
math-
ematical
notation
that
is
the
primary
advantage
of
the
algebraic
interface.
302
C:
Notes
for
Algebraic
Calculator
Users
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