Radio Shack TRS-80 User Manual page 158

where the
triangle
looks like this:
A
= 3
B
=
4
Okay. That's not too grim.
So
let's
write a
program to find the value of L,
when
A
=
3
and
B
=
4. If
we
had
the
built-in
square root function
(which
we
don't),
our program might look
like this
:
10
REM
*
SQUARE ROOT SOLUTION WITH SUBROUTINE
*
20
IN.
"THE LENGTH
OF
SIDE
A =
";A
30 IN.
"THE LENGTH
OF
SIDE
B =
";B
40
L
=
SQR(A*A
+
B*B)
50 P.
"A", "B"
,
"L"
60
P. A ,B ,L
Now
type in the
program
carefully
and
RUN.
Caarash!
The
WHAT?
40
L=S?QR(A*A
+
B*B)
tells
us the
Computer does not recognize
SQR. That means
we'll
have
to call
up the
SQR
subroutine
from Appendix
A
to
make
a
workable program.
See the
list at
the end of
this
Chapter
to
determine
which functions
are available as
sub-
routines in
Appendix
A.
Turn
to page
216
of
Appendix
A
and
find the
Square Root Subroutine.
There are three
important
things to
look
for
when checking out any subroutine:
1.
What
is
the
input variable?
2.
What
is
the
output
variable?
156
Whenever you come
across
a
program
with
aft
intrinsic
function
you
don't
have, you'll go
";t&roagh
this
same procedure. First type in the
§|
subroutine,
then
make
a
few minor changes
in
ed.to#ei^t^;-
:
:
: