H
# empty insert at address 0 should set the current address to 0
0i
.
+4i
# this is not a comment
.
# empty insert at current address should not modify the current address
i
.
i
hello world!
.
i
hello world!!
.
0i
hello world!!!
.
i

second line

.
$i
hello world!!!!
.
u
u
i
hello world!!!!!
.
i
to be undone
.
u
w out.o