Well, the U.S. Navy's system was not that sophisticated.
The screen showed the operator what objects were detected on radar, and if he clicked on an object, it would track it. But if the operator wanted to get more information about the object (in this case, by listening in on its radio signals) to find out what it actually was, he had to move a separate cursor and click on the object again.
"In order to see what direction the object is moving, you'll need a soldering gun."
It's clumsy and unintuitive, and it made it really easy to forget which thing they were highlighting at any given moment -- the operator can be tracking one object and have it display the information for a completely different one because he forgot to move the other cursor. It's the kind of user interface that wouldn't make it out of the testing phase of a cheap browser game. And it cost the passengers of the plane their lives.
That's because the operator in the USS Vincennes thought he was listening to the incoming aircraft (the Airbus full of innocent people), because that's the thing he selected, when he was actually receiving signals from a parked F-14 several miles away, because that's where his other cursor was.
"Patch v1.4 fixed a bug that occasionally leads to missiles being fired at planes full of innocent people."