Apple IIe - Page 129

Apple
BASIC
Reference
Guide
129
80
PRINT
"YOU
ENTERED
A
TWO"
90
GOTO
130
100 PRINT
"YOU
ENTERED
A THREE"
110
GOTO
130
120
PRINT
"YOU
ENTERED
A
FOUR"
130
END
In
the
preceding
example
,
line
10
prompts
the
user
to
enter
a
number
between
one
and
four.
In
line
20,
an
ON
...
GOTO
will
branch
control
to
a
different
line
depending
on
the
value
of
I.
If
I
is
one,
program
execution
will
branch
to
60.
If
I
is
two
,
program
execution
will
branch
to
80,
etc.
If
zero
or
a
number
greater
than
four
was
entered
,
program
execution
will
continue
to
line
30.
ONERR
GOTO
•
Applesoft
o
Integer
The
ON
ERR
statement
allows
errors
to
be
trapped.
The
statement
then
transfers
program
control
to
an
error
handling
routine
at
the
indicated
line
number
.
Configuration
ONERR
GOTO
line
line
is
the
first
line
of
the
error
handling
routine.
ON
ERR
GOTO
should
be
executed
before
the
error
has
occurred.
When
Applesoft
executes a
program
,
it
executes
the
program
line
by
line.
If
an
error
occurs
during
program
execution
,
Applesoft
will
check
to
see
if
an
ONERR
GOTO
statement
has
been
executed.
If
no
ONERR
GOTO
statement
had
been
executed
,
Applesoft
will
halt
program
execution
and
display
the
error.
Otherwise
the
program
will
branch
to
the
line
i
nd
icated
in
I
the
ONERR
GOTO
statement
.
POKE
216
,0
turns
off
any
previously
executed
ONERR
GOTO
statement.