Transmits a device control string to a device driver.
IOCTL[#]file_number, control_string
file_number is the file number assigned to the device in its OPEN statement.
control_string is a string expression that specifies the command to send to the device.
IOCTL commands are generally 2 to 3 characters followed by an optional alphanumeric argument. An IOCTL string may be up to 255 bytes long, with commands within the string separated by semicolons.
If a user had installed a driver to replace LPT1, and that driver was able to set page length (the number of lines to print on a page before issuing a form feed), then the following lines would open the new LPT1 driver and set the page length to 66 lines:
OPEN "LPT1:" FOR OUTPUT AS #1
IOCTL #1, "PL66"
The following statements open LPT1 with an initial page length of 56 lines:
OPEN "\DEV\LPT1" FOR OUTPUT AS #1
IOCTL #1, "PL56"