Commodore CBM - Open

The specified index is evaluated and, if necessary, truncated to an integer
number. If
index=l, a branch is taken to the statement with line number linel' If
index=2, a branch
is taken to the statement with line number line2. If index=3, a
branch
is taken to the statement with line number line3' If index=O, no branch is
taken. If index is in the allowed range but there is no corresponding line number in
that position of the line number
list no branch is taken. If a branch is not taken,
program control proceeds to the next statement
following the ON ... GOTO. The
next statement may
be on the same line as the ON ... GOTO (separated by a co-
lon).
If index has any value other than zero outside the allowed range, the pro-
gram aborts
with an error message. As many line numbers may be specified as
will fit on the SO-character line.
ON ... GOTO is normally executed in program mode. It may be executed in
immediate mode
as long as there are corresponding line numbers in the current
stored program
that may be branched to.
Example:
OPEN
40 A=B< 10
50
ON A+2 GOTO 100,200
50
X=X+l
60 ON X GOTO 500,600,700
70
Branch to statement 100 if A
is true
(-1) or branch to statement 200 if A
is false (0).
Branch to statement 500
if
X=l, to statement 600
if
X=2, or to statement 700
if X=3. No branch
is taken if
X>3
The OPEN statement opens a logical file and readies the assigned physical
device.
Format:
OPEN
file
file,device
file,device,s
fi le.device.s,fi lename
Open code 0 of device 1
and assign file.
Open code 0 of device and
assign file.
Open code s of device and
assign file.
Open filename, code
s, of
device and assign file.
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