Format of PC-MOS/386 Task File Block:
Offset	Size	Description	)
 00h	BYTE	signature byte "H" if allocated from system memory pool
 01h	BYTE	header block ID, "F" = task 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
---TFB---
 10h	WORD	segment address of next TFB
 12h	WORD	segment address of previous TFB
 14h	WORD	segment address of TFB's Global File Block (see #04011)
 16h	WORD	segment address of owner's PSP
 18h	WORD	file handle
 1Ah  3 BYTEs	???
 1Dh	DWORD	file position
 21h  4 BYTEs	???
 25h	BYTE	IOCTL flags (see #04010)
 26h  2 BYTEs	???