cmpb	i.uid,u.uid / is user same as owner of file
	bne	1f / no, then branch
	asrb	r2 / shift owner read write bits into non owner
		   / read/write bits
	asrb	r2
1:
	bit	r2,(r0)+ / test read-write flags against argument in
			 / access call
	bne	1f
	tstb	u.uid
	beq	1f
	jmp	error
1:
	rts	r0

setimod:
	movb	$1,imod / set current i-node modified bytes
	mov	s.time,i.mtim / put present time into file modified time
	mov	s.time+2,i.mtim+2
	rts	r0

imap: / get the byte that has the allocation bit for the i-number contained
      / in r1
	mov	$1,mq / put 1 in the mq
	mov	r1,r2 / r2 now has i-number whose byte in the map we
 		      / must find
	sub	$41.,r2 / r2 has i-41
	mov	r2,r3 / r3 has i-41
	bic	$!7,r3 / r3 has (i-41) mod 8 to get the bit position
	mov	r3,lsh / move the 1 over (i-41) mod 8 positions to the left
		       / to mask the correct bit
	asr	r2
	asr	r2
	asr	r2 / r2 has (i-41) base 8 of the byte no. from the start of
		   / the map
	mov	r2,-(sp) / put (i-41) base 8 on the stack
	mov	$systm,r2 / r2 points to the in-core image of the super
			  / block for drum
	tst	cdev / is the device the disk
	beq	1f / yes
	add	$mount-systm,r2 / for mounted device, r2 points to 1st word
				/ of its super block
1:
	add	(r2)+,(sp) / get byte address of allocation bit
	add	(sp)+,r2 / ?
	add	$2,r2 / ?
	rts	r0

iget:
	cmp	r1,ii / r1 = i-number of current flle
	bne	1f
	cmp	idev,cdev / is device number of i-node = current device
	beq	2f
1:
	tstb	imod / has i-node of current file been modified i.e.,
	       	     / imod set