Texas Instruments TI Programmable 57

SUBROUTINES:
AND
To Use Susroutines RIGHT FROM THE KEYBOARD:
One advantage of using subroutines in a program is that you can use
any subroutine in the program separately from the program itself. Todo
this, just press n while out of “learn’’ mode: The program pointer will
immediately
go
to
label
n
and
execute
the
subroutine.
In
this
case
the
[INV]
key
sequence
at
the
end
of
the
subroutine
will
act
just
like
an
instruction.
Notes On SuBROUTINES:
Using subroutines is good programming practice! Subroutines let you
organize your programs easily (and thus can help you find errors — if
they
exist.)
It's
also
easier
for
other
programmers
to
understand
and
use
your programs when they're in bite-size subroutine "'chunks”’.
Your
calculator
is
equipped
with
two
levels
of
subroutine
capability.
This
means
that
while
you're
inside
one
subroutine,
you
can
“‘call"
or
use
another
subroutine.
You
can't
go
to
a
third
level,
however.
If
a
second
level
subroutine
tries
to
‘call’
a
third,
a
flashing
error
condition
will
be
created.
The
“subroutine
return’
memory
has
room
for
only
two
return
locations.
You
can
easily
write
any
of
your
programs
so
that
they
can
be
used
as
subroutines
in
other
programs.
(In
fact,
most
experienced
programmers
suggest
that
you
do
this.)
Naturally,
this
won't
be
practical
for
programs
that
contain
close
to
50
steps
—
but
it’s
a
good
procedure
to
follow
for
any
shorter
programs,
To
do
this,
just
start
the
program
with
a
label,
and
end
it
with
an
[iN]
key
sequence.
The
[INV]
key
sequence
acts
just
like
an
instruction
if
the
subroutine
return
memory
is
empty.