Q:
The
keys
from
[IJ
to
[[)
don't
work.
What
is
wrong?
A:
You
accidentally selected
Menu
Lock, so
the
keys from
[IJ
to
[[)
select
menus
unless you press • first.
To
turn
off
Menu
Lock,
press
.1
MENUS
I.
Q:
I can't find
some
variables that I used
earlier.
Where
did
they
go?
A:
You
may
have
been
using
the
variables in a
different
directory.
If
you
can't
remember
which
directory you were using,
you'll
need
to
check all
the
directories.
Q:
How
can
I determine
how
much memory
is
left?
A:
Execute
t'lEt1
1 ENTER 1 to
return
the
number
of
bytes
available
in
memory.
Q:
Why
did
the cursor change
its
appearance?
A:
The
cursor indicates
the
current
entry
mode.
The
entry
modes
are
Immediate
(empty
cursor), Algebraic (partly filled cursor),
or
Alpha
(filled cursor).
The
shape
of
the
cursor
indicates
Replace
mode
(box
cursor)
or
Insert
mode
(arrow cursor). See
"How
the
Cursor
Indicates
Modes"
on
page
172.
Q:
I keyed
in
a name
(or
pressed a
USER
menu
key),
but the name didn't
go
on
the
stack.
Why
not?
A:
You
entered
an
unquoted
name,
which
refers to
the
contents
of
a
variable.
To
put
a
name
on
the
stack, press
~
first. (See
"Quoted
and
Unquoted
Names"
on
page
57.)
Q:
When
I calculate the
cube
root
of
-27,
why isn't
the
result
-3?
A:
Every
number
has
three
cube
roots, two
of
which
are complex
numbers.
The
HP-28S
returns
one
of
the
three
roots, called
the
princi-
pal value. For positive real
arguments
the
principal value is
the
real
root; for
negative
real
arguments
the
principal value is
one
of
the
complex roots.
To
calculate
the
real bth
root
of
a real
number
a,
key
in
the
following
program.
Press
~
RROOT 1 STO 1 to store
the
program
in a variable RROOT
(real
root).
You
can
then
find
the
real
cube
root
of
- 27
by
typing
27 1 CHS 1
1 ENTER 1 3 1 ENTER 1 RROOT 1 ENTER I.
284
A:
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