Radio Shack TRS-80 User Manual page 70

As
the screen
shows,
we
"bailed
out" of the
A
loop
when
A
equalled 2
and
hit the test line
at 55-
The
END
in line
99
is
just
a precautionary
roadblock
set
up
to
stop the
Computer
from
running into
line
100 unless specifically
directed to
go
there.
That would
never
happen
in this
simple
program, but
we
will
use protective
ENDs
from
time to time
to
remind us
that
lines
which should be reached only
by
specific
GOTO
or
IF-THEN
statements must
be
protected against accidental "hits".
We'll
be seeing a lot
of the nested
FOR
-NEXT
loop
now
that
we know what
it is
and can
put
it
to use
.
EXERCISE
13-1: Enter the original
program found
at
the beginning of
this
Chapter.
It
contains a
B
loop
nested within the
A
loop.
Make the necessary additions to this
program
so
a
new
loop called
"C"
will
be
nested within the
B
loop,
and
will
print
"C
LOOP"
4 times
for
each pass
of the
B
loop.
EXERCISE
13-2: Alter the resident
program
so that
it
is
the
same
as
that
found
in
the
answer to Exercise
13-1.
Make the necessary additions to
this
program
so
a
new
loop
called
"D"
will
be
nested within
the
C
loop,
and
will print
"D
LOOP"
5
times for
each
pass
of the
C
loop.
Learned
in
Chapter 13
Miscellaneous
Nested
FOR-NEXT
loops
Protective
END
blocks
68