Has she turned on the computer yet?
No, she hasn't
Has she turned down the volume yet?
No, she hasn't
????
I've just turned off the computer
Has he turned off the computer yet?
Yes, he has
...not...
I haven't logged in to the website yet
....(not turn on the volume)...
I haven't turned on the volume yet
???????
I've logged out of the website
....not....
I haven't turned on the computer yet
????
I've just turned up the volume