Clearing
the
Display and Menu Variables
The
.1
CLEAR
ALL
I key is a powerful clearing feature:
• Pressing
.1
CLEAR
ALL
I always clears
the
history stack.
•
If
the
current
menu
consists
of
variables (for example, COST,
PRICE,
and
M%C
in
the
MU%C menu), those variables are cleared
to
O.
•
If
the
HP-18C
is
displaying a
number
list
or
formula list,
.1
CLEAR
ALL
I clears all
the
information
from
the
list. Clearing
num-
ber
lists is covered in
chapter
7;
clearing
the
formula
list is covered
in
chapter
9.
When
the
HP-18C
Doesn't
Understand What
You Want
Suppose
you tried to calculate
the
markup
on
cost
without
storing a
value for COST. COST
would
have
a value
of
0,
and
the
calculator
would be
unable
to
do
the
calculation.
To
help
you correct
the
situa-
tion,
the
HP-18C
beeps
and
displays a message.
The
message is
erased from
the
display the next time you press a key.
Refer to
appendix
C for
additional
information
about
error messages.
Custom Menus
The
HP-18C
has
a set
of
built-in formulas
used
by
some of its menus.
For instance,
the
markup
calculations
on
the
previous pages use a for-
mula
stored
permanently
in calculator memory.
The
HP-18C
lets you
enter
your
own
formulas
into
memory,
which
are
then
used
to create
menus
customized for your particular
needs-
custom
menus. Creating
and
using
custom
menus
is
done
by
the
for-
mula
solver,
which
is covered
in
chapter
9.
1:
Starting
to
Use
the
HP-18C
31
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