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IOCTL Statement Details
 
Syntax
  IOCTL [#]filenumber, string
 
The filenumber is the BASIC file number used to open the device.
The string is the command sent to the device. Commands are
specific to the device driver. See the documentation for the device
driver to find out what the valid IOCTL commands are. An IOCTL
control data string can be up to 32,767 bytes long.
 
The IOCTL statement works only if all three of the following
conditions are met:
 
  1. The device driver is installed.
  2. The device driver states that it processes IOCTL strings. See
     the documentation for the driver. You can also test for IOCTL
     support through DOS function &H44 by using interrupt &H21 and the
     CALL INTERRUPT routine. See the Microsoft MS-DOS Programmer's
     Reference and the CALL INTERRUPT statement for more information.
  3. BASIC performs an OPEN on a file on that device, and the file is
     still open.
 
Most standard DOS device drivers do not process IOCTL strings,
and you must determine if the specific driver accepts the command.