Let's look at a typical novice's session with the mighty ed:

golem$ ed

?

help

?

?

?

quit

?

exit

?

bye

?

hello?

?

eat flaming death

?

^C

?

^C

?

^D

?

---

Note the consistent user interface and error reportage. Ed is generous enough to flag errors, yet prudent enough not to overwhelm the novice with verbosity. [1]

[1] https://www.gnu.org/fun/jokes/ed-msg.html