Arguments

 

fandle

   OpenVMS usage:fandle
   type:         64-bit integer (unsigned)
   access:       read only
   mechanism:    by value
   A fandle returned by a previous call to $IO_SETUP.
 

chan

   OpenVMS usage:channel
   type:         word (unsigned)
   access:       read
   mechanism:    by value
   Software I/O channel number.
 

iosadr

   OpenVMS usage:address
   type:         address
   access:       read only
   mechanism:    by value
   Address of the I/O Status Area (IOSA). This value cannot be 0;
   that is, an IOSA is required. The iosadr must be aligned to a
   quadword boundary.
 

bufadr

   OpenVMS usage:char_string
   type:         address
   access:       read only
   mechanism:    by value
   The process buffer address. Must be aligned on a 512-byte
   boundary.
 

buflen

   OpenVMS usage:byte count
   type:         64-bit integer
   access:       read only
   mechanism:    by value
   The byte count for the I/O. The buflen argument must be a
   multiple of 512 bytes. Drivers have further limitations on the
   maximum size of an I/O request.
 

devdata

   OpenVMS usage:address
   type:         pointer or integer
   access:       read only
   mechanism:    by value
   A hardware integer passed unchanged to the driver. For disk
   devices, this is the media address for the transfer; that is,
   the virtual block number (VBN) for virtual I/O functions or
   the logical block number (LBN) for logical I/O functions. This
   argument is ignored for tape devices.

   For drivers with complex parameters, devdata would be the address
   of a descriptor or buffer specific to the device and function and
   would be documented with the driver.