Format of PC-MOS/386 Global File Block:
Offset	Size	Description	)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "G" = global file block
 02h	WORD	length of block in paragraphs
 04h	WORD	segment address of next header block (0000h if last)
 06h	WORD	segment address of previous header block (0000h if first)
 08h	WORD	pointer to next TCB
 0Ah	WORD	pointer to previous TCB
 0Ch	WORD	pointer to associated TCB (if applicable)
 0Eh	WORD	reserved
---GFB---
 10h 10 BYTEs	???
 1Ah	WORD	file attribute
 1Ch	BYTE	???
 1Dh	DWORD	address of device driver
 21h	WORD	first cluster
 23h	WORD	time of last modification
 25h	WORD	date of last modification
 27h	DWORD	size of file in bytes
 2Bh 11 BYTEs	???
 36h 11 BYTEs	device name or FCB-format filename
 41h	WORD	segment address of TFB list
 43h	WORD	segment address of first RLB (see #04014) (0000h = none)
 45h	BYTE	flag: nonzero if GFB refers to character device
 46h	WORD	address of Block Device Block (see #04013)
 48h	WORD	sector of file's directory entry (see #01352)
 4Ah	WORD	high word of file's directory entry
 4Ch	WORD	ofsset of directory entry within sector