section .bss

		; default drive if field in FCB = 0
defdrv:		resb 1

section .text
		; Functions here generally expect the FCB to be at ES:BX

		; Helper function: read the drive number from FCB,
		; apply default if necessary,
		; and make it current I/O drive
setdrv:		mov dl, [es:bx+fcb.drive] ; A=1
		test dl, dl
		jnz .nofix
		mov dl, [defdrv] ; A=0
		inc dl
		mov [es:bx+fcb.drive], dl ; A=1
		; now set as current i/o drive
.nofix:		dec dl ; A=0 for dsksel
		jmp dsksel

		; FCB open
fcbopn:		; call fcbfst
		; copy match
		; store cluster number in fcb
		; record = 0
		ret

		; FCB close
fcbcls:		; flush disk buffer
		ret

		; FCB find first
fcbfst:		mov word [es:bx+fcb.dirpos], 0
		; FCB find next
fcbnxt:		call setdrv
		; load rootdir sector from state
		; search until next match
		; next sec & loop if mismatch
		; err exit if no further matches
		ret

		; FCB delete file
fcbdel:		; call fcbfst
		; get search state, load root dir from there
		; mark file as deleted
		; mark buffer dirty
		ret

		; FCB read
		; read sector from cluster into diskbuf
fcbrd:		; read record from sector
		; advance record num, carry over to cluster
		ret

		; FCB write
fcbwr:		; read sector from cluster into diskbuf
		; write record into sector
		; mark buffer dirty
		; advance record num, carry over to cluster
		ret

		; FCB create
fcbcre:
		ret

		; FCB rename
fcbren:
		ret