◄Blk► This asks the driver to determine whether the media in the drive has been changed. DevReq01Rec Offset Size Contents ▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ +0 1 bLen 13H (length of this request packet) +1 1 bUnitNo unit number to check +2 1 bCmd 01H (command code) +3 2 rStatus OUTPUT: Device Status Word must fill before exit +5H 8 res (reserved) +0dH 1 bMediaID INPUT: Media Descriptor DOS thinks is there +0eH 1 bRetFlag OUTPUT: ffH=no change 00H=don't know 01H=changed +0fH 4 pfVolID OUTPUT: Addr of ASCIIZ▲ volume ID (3.0+) 19 size of this structure rStatus On exit, the driver must place a DevStatusWord here. Always set the Done bit (bit 8). On an error, set the Done bit and the Error bit (bit 15) and put a Device Error Code in the low byte. bMediaID On entry, this contains the Media Descriptor byte of the disk that DOS thinks is in the drive. bRetFlag On exit, you must set this to indicate whether a different disk is in the drive. If you support Removable Media, and return ffH, you must set pfVolID. pfVolID With DOS 3.0+ drivers that support Removable Media (see Device Attribute), you should set this to the address of an ASCIIZ▲ string of the volume label of the drive that was previously in the drive. Then, when DOS issues critical error 0fH (see INT 24H), it can prompt the user to insert the right disk. If you don't know the volume label, put the address of the string "NO NAME" here. Notes: ■ Diskette performance is much faster when the device driver can quickly indicate a "no change", since DOS need not re-read the FAT on the disk before each disk access. See Also: Device Requests DevRequestHdrRec Installable Device Drivers -♦-