Misc: in computing what does DOS stand for?

Questions

What was the real name of the hospital on St. Elsewhere??

In the show "The Equalizer",what did the hero (McCall) call his former superior from the "agency"??

On "Out of This World" what planet was Troy from??

What was the Saved by the bell series with Hayley Mills originally called??

What was the name of He-man's legless,wizard friend??