hello world in UNIX V6 (PDP-11)

a.c

main(){write(1,"hello\n",6);}

a.s

a.out:     file format a.out-pdp11

00000000 <.text>:
start:
   0:	f009           	setd
   2:	1180           	mov	sp, r0
   4:	1226           	mov	(r0), -(sp)
   6:	0bd0           	tst	(r0)+
   8:	1036 0002      	mov	r0, 2(sp)
   c:	09f7 0008      	jsr	pc, 0x18
  10:	100e           	mov	r0, (sp)
  12:	09df 0054      	jsr	pc, *$0x54
  16:	8901           	sys	1
_main:
  18:	0977 0042      	jsr	r5, 0x5e
; write(1,"hello\n",6);
  1c:	15ce 0006      	mov	$6, (sp)
  20:	15e6 0088      	mov	$0x88, -(sp)
  24:	15e6 0001      	mov	$1, -(sp)
  28:	09df 0032      	jsr	pc, *$0x32
  2c:	2596           	cmp	(sp)+, (sp)+
  2e:	0077 003a      	jmp	0x6c
_write:
  32:	1166           	mov	r5, -(sp)
  34:	1185           	mov	sp, r5
  36:	1d40 0004      	mov	0x4(r5), r0
  3a:	1d77 0006 0052 	mov	0x6(r5), $0x92
  40:	1d77 0008 004e 	mov	0x8(r5), $0x94
  46:	8900           	sys	0
  48:	0090           	.word	0x90
  4a:	8602           	bcc	0x50
  4c:	0077 002a      	jmp	0x7a
  50:	1585           	mov	(sp)+, r5
  52:	0087           	rts	pc
_exit:
  54:	1166           	mov	r5, -(sp)
  56:	1185           	mov	sp, r5
  58:	1d40 0004      	mov	4(r5), r0
  5c:	8901           	sys	1
csv:
  5e:	1140           	mov	r5, r0
  60:	1185           	mov	sp, r5
  62:	1126           	mov	r4, -(sp)
  64:	10e6           	mov	r3, -(sp)
  66:	10a6           	mov	r2, -(sp)
  68:	0be6           	tst	-(sp)
  6a:	0048           	jmp	(r0)
cret:
  6c:	1141           	mov	r5, r1
  6e:	1844           	mov	-(r1), r4
  70:	1843           	mov	-(r1), r3
  72:	1842           	mov	-(r1), r2
  74:	1146           	mov	r5, sp
  76:	1585           	mov	(sp)+, r5
  78:	0087           	rts	pc
cerror:
  7a:	1037 0018      	mov	r0, $0x96
  7e:	15c0 ffff      	mov	$-1, r0
  82:	1146           	mov	r5, sp
  84:	1585           	mov	(sp)+, r5
  86:	0087           	rts	pc

00000088 <.data>:
  88:	68 65 6c 6c 6f 0a 00 00	"hello\n"
  90:	8904
  92:	0000
  94:	0000

00000096 <.bss>:
_errno:
  96: