16 bit multiplication

org 00h
mov r0,#42h
mov r1,#44h
mov a,@r0
mov b,@r1
mul ab
mov r2,a
mov r3,b  ;result 1 in r2 and r3
dec r0
mov a,@r0
mov b,@r1
mul ab
mov r4,a
mov r5,b  ;result 2 in r4 and r5
inc r0
dec r1
mov a,@r0
mov b,@r1
mul ab
mov r6,a
mov r7,b ;result 3
dec r0
mov a,@r0
mov b,@r1
mul ab  ;result 4
mov 50h,a
mov 51h,b
mov 63h,r2
mov a,r3
add a,r4
mov 62h,a
mov a,r5
addc a,#00
mov 61h,a
mov a,63h
mov 73h,a
mov a,r6
add a,62h
mov 72h,a
mov a,r7
add a,50h
mov 64h,a
mov a,51h
addc a,#00h
mov 51h,a
mov a,61h
add a,64h
mov 71h,a
mov 70h,51h
sjmp $
end