To allow GW-BASIC to read a "control data" string from an open character device driver.
file number is the file number open to the device.
The IOCTL$ function is generally used to get acknowledgement that an IOCTL statement succeeded or failed. It is also used to get device information, such as device width after an IOCTL statement requests it.
10 'GW is a possible command 20 'for get device width 30 OPEN "\DEV\MYLPT" AS#1 40 IOCTYL#1, "GW" 50 'Save it in WID 60 WID=VAL(IOCTL$(#1))