Format of FCB reserved field for DOS 5.0:
Offset	Size	Description	)
 18h	BYTE	number of system file table entry for file
 19h	BYTE	attributes
		bits 7,6: 00 = SHARE.EXE not loaded, disk file
			  01 = SHARE.EXE not loaded, character device
			  10 = SHARE.EXE loaded, remote file
			  11 = SHARE.EXE loaded, local file or device
		bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file---
 1Ah	WORD	starting cluster of file on disk
 1Ch	WORD	unique sequence number of sharing record
 1Eh	BYTE	file attributes
 1Fh	BYTE	unused???
---SHARE.EXE loaded, remote file---
 1Ah	WORD	network handle
 1Ch	DWORD	network ID
---SHARE not loaded, local device---
 1Ah	DWORD	pointer to device driver header (see #01646)
 1Eh  2 BYTEs	unused???
---SHARE not loaded, local file---
 1Ah	BYTE	extra info
		bit 7: read-only attribute from SFT
		bit 6: archive attribute from SFT
		bits 5-0: high bits of sector number
 1Bh	WORD	starting cluster of file
 1Dh	WORD	low word of sector number containing directory entry
		(see #01352)
 1Fh	BYTE	number of directory entry within sector