Commodore Plus 4 - Page 153

OPEN 0PEN ffle #. device # [.secondary address \ [/'filename, type, mode"]
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The OPEN statement allows the Plus/4 to access devices such as the
cassette recorder and disk for data, a printer, or even the screen of the
Plus/4. The word OPEN is followed by a logical file number, which is the
number to which all other BASIC statements will refer. This number is
from 1 to 255. There is always a second number after the first called the
device number. Device number 0 is the Plus/4 keyboard, 3 is the Plus/4
screen, 1 is the cassette recorder. 4 is the printer. 8 is usually the disk.
A zero (0) may be included in front of the device number digit (e.g., 08
for 8, which are interchangeable for the Plus/4). It is often a good idea
to use the same file number as the device number because it makes it
easy to remember which is which. Following the second number may
be a third number called the secondary address. In the case of the
cassette,
this can be 0 for read, 1 for write, and 2 for write with end-
of-tape marker at the end. in the case of the disk, the number refers to
the channel number. In the printer, the secondary addresses are used
to set the mode of the printer. See the Plus/4 Programmer's Reference
Manual or the manua^ for each specific device for more information for
more on secondary addresses. There may also be a string following
the third number, which could be a command to the disk drive or the
name of the file on tape or disk. The type and mode refer to disk files
only, (File types are prg.seq, rel, and usr; modes are read and write.)
EXAMPLES;
10 OPEN 3,3
10 OPEN 1,0
20 OPEN 1,1,0,"DOT"
OPEN 4,4
OPEN 15,8,15
OPENS the SCREEN
as a device.
OPENs the keyboard
as a device.
OPENs the cassette
for reading, file to be
searched for is
named DOT
OPENs a channel to
use the printer.
OPENs the command
channel on the disk.
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