H

# empty append at address 0 should set the current address to 0

0a

.

+4a

# this is not a comment

.

# empty append at current address should not modify the current address

a

.

a

hello world!

.

a

hello world!!

.

0a

hello world!!!

.

!read one	# shell escape should not modify the current address

text for the read shell command above

a

shell escape marker

.

$a

hello world!!!!

.

u

u

a

hello world!!!!!

.

a

to be undone

.

u

w out.o