Atari 800

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You
can also use
your
ATARI 800 as a calculator.
Use
the
Print
command to
make
your
ATARI 800 evaluate
arithmetic expressions.
After
the
BASIC
prompt
type:
Don't
forget Print!
Press
ffffi[f
.
Here's
your
answer!
You
can enter
any expression and the
ATARI 800 will do the arithmetic.
Remember that BASIC language does
not
tell
you
the
correctexpression to use to
solve number
problems.
You mustfigure out how to calculate
in-
terest
payments,
sales commissions,
expected time of arrival, orwhateveryou
wantto
know. BASIC does have
a
large repertoire
of
arithmetic, algebraic, and trigonometric
functions
available.
But
you,
the
programmer,
must still
tell
the computer
how
to
combine them to
produce
meaningful results. You will
find
a complete
discussion of
BASIC
language arithmetic
in
Section
3 of
Chapter
2 and Appendix L-of Atari BASIC Programm-
ing
Guide.
The ATARI 800
evaluates expressions
in
the same way
you
were
taught to do
it in
elementary school.
Everything inside
parentheses
Owill
be done
f irst,
then exponentiation
^
. Exponentiation means multiplying a
number
times
itself several times. For example, 5
^
3 means
5 times 5 times 5 and is equal
to
125. You will often
see
this
expression written 53. lt is read
"f
ive raised
to the third
power".
Type
the
exponentiation symbol on
the
computer by
pressing
!@
and
$
.
All multiplication
*
and division
/
is done next. Addition
*
and
subtraction
-
are
performed
last. lf
you
have forgotten
that the order in which calculations are done is impor-
tant, try a
few
problems.
You
will
find
that(4*6)15:2 while 4*6/5:5.2
and 415*6:6.8.
The ATAR!800 will
print
any whole
number value in the range
-999999999
to 999999999
as
a
whole
number.
lt
will
express
fractions and numbers outside this
range in scientific notation as a decimal
number
between one
and ten as a
power
of
ten. For example,
if
the
value
of
your
expression is 1234567891
the
ATARI 800 will write it
as1.23456789E+9, which
means move the decimal
point
nine
places
to the
right. You read
this
number
as
1.23456789
times ten to
the ninth
power
(1,000,000,000).
Spend some time
familiarizing
yourself
with the way the ATARI 800
handles numbers. Notice again that
your
computer does not
provide
the correct
method for
solving a
problem
involving numbers.
lt
only does the
arithmetic
on the
numbers
you
give
it.
You have been
using
the Atari BASIC Language
in
the
immediate mode. This means
that the
ATARI 800
follows
your
command as soon as
you
give
it
and then
forgets
about
it. ln
program
mode,
you
may
give
the computer
abouttwo hundred Iines of
instructions. Each line is
stored until the
RUN command
is
entered.
Then the com-
puter
follows
one
instruction after another until the whole task
is
completed.
r,