Format of parameter block for function 6Fh: Offset Size Description ) 00h BYTE (call) length of this buffer (in bytes) 01h BYTE (ret) number of bytes in parameter block actually used 02h BYTE (ret) drive flags (see #01571) 03h BYTE (ret) physical drive number 00h-7Fh floppy 80h-FEh hard FFh no physical drive 04h DWORD (ret) bitmap of logical drives associated with physical drive bit 0 = drive A:, etc. 08h QWORD (ret) relative block address of partition start