NAME
       OpenDevice - open a cd unit for access

   SYNOPSIS
       error = OpenDevice("cd.device", UnitNumber, iorequest, flags);
       D0                 A0           D0          A1         D1

   FUNCTION
       Opens the cd.device and creates an iorequest for use in accessing
       the CD.

   INPUTS
       UnitNumber - Normally zero; however, this is described as:
                    Ones digit      = unit (scsi unit number)
                    Tens digit      = LUN (disk within disk changer)
                    Hundreds digit  = Card number (SCSI card)
                    Thousands digit = Reserved (must be zero)
       iorequest  - pointer to a struct(iostdreq)
       flags      - Should be zero.

   RESULTS
       error        0 = success, otherwise this is an error.

   NOTES

   SEE ALSO
       closedevice()