Texas Instruments TI Programmable 57

Using subroutines is not only a handy technique for saving program
steps and breaking a large program down into easy to analyze
segments:
it's
also
just
plain
good
programming
practice.
A
subroutine
is
just a "miniprogram” you can write as part of any program. Anytime you
need
to
use
a
set
of
program
steps
more
than
once
in
a
program,
it's
a
good
idea
to
make
that
series
of
steps
into
a
subroutine.
Here's
how:
To
make
any
series
of
program
steps
into
a
subroutine,
all
you
need
to
do
is:
-Start the series of program steps with a Label.
-End
the
series
of
steps
with
an
LIN]
key
sequence.
Subroutines
can
be
of
any
length,
as
long
as
your
entire
program
with
all
its
subroutines
is
no
more
than
50
steps.
To Use A SuBROUTINE IN A PROGRAM:
‘While in “learn’' mode, anytime you need to use
any subroutine, just press: n, where n is the label of the
subroutine.
You
can
use
(or
“call’’,
as
is
sometimes
said),
a
subroutine
as
many
times
as
you'd
like
in
a
program.
When
the
program
pointer
comes
to
a
n
key
sequence
in
a
program,
the
calculator
does
the
following
things
for
you
(illustrated
in
the
diagram);
(1) First, it “notes’’ the step in the
program where the n
instruction occurs in a special i
Calculator remembers
next program step.
memory (called the subroutine
return memory). bk
(@ The program pointer goes E
tight to label n and starts
executing the instructions after
it, until it comes to the [Nv]
instruction.
() When the program pointer
reaches the [INV)
instruction, it returns to the
point where the subroutine
was "called", and continues.
SusRourTine
3-11