HelpPC 2.10	Quick Reference Utility	Copyright 1991 David Jurgens
Device Request Header Format     Offset Size                Description        00   byte       length in bytes of the request header        01   byte       unit code;  the sub-unit the operation is for (block                        devices);  meaningless for character devices        02   word       command code, (see DEVICE COMMANDS)        04  8bytes      reserved for DOS        0C  nbytes      request data  (variable length)        - see  INT 21,44  or    DEVICE ATTRIBUTES  or  DEVICE CODES        - see also  IOCTL,n where "n" is an IOCTL function
Esc or Alt-X to exit	device request headr	Home/PgUp/PgDn/End ←↑↓→