Format of MS-DOS 5+ UMB control block:
Offset Size Description )
00h BYTE type: 5Ah if last block in chain, 4Dh otherwise
01h WORD first available paragraph in UMB if control block at start
of UMB, 000Ah if control block at end of UMB
03h WORD length in paragraphs of following UMB or locked-out region
05h 3 BYTEs unused
08h 8 BYTEs block type name: "UMB" if start block, "SM" if end block in UMB
SeeAlso: #01628,#01631