A lot of specialty computer systems used in movies are actually surplus computers. For instance, in the movie *Eve of Destruction* (yeah, I’ve never heard of it either) part of an IBM AN/FSQ-7 from the Semi-Automatic Ground Environment detection and control system was used. Although it looks pretty dated, even for 1991, apparently the set designers thought it looked futuristic. Actually, this one seems to have gotten around like the cheerleading squad, as has the DEC PDP series. The “W.O.P.R.” console used in WarGames (which, according to Wikipedia stands for “War Operation Plan Response”) is just a prop; however, a IMSAI 8080 used by Broderick was the real thing, if about as powerful as a calculator wristwatch.
As for the purpose of the blinking lights, believe it or not back before the day of multifunctional display terminal, window paging systems, Graphic User Interfaces, et cetera a lot of diagnostic and functional information could be read from the diagnostic (flashy light or “blinkenlight”) console. Of course, this is back in the day when programmers would spend days fiddling with the data write sequence to make retrieval faster. You could still program a computer to output analog signals to write to a light console; see the BeBox and the Connection Machine both had panels of blinkenlights, albeit more for geek catchet than any practical purpose. In Neil Stephenson’s Cryptonomicon, the main protagonist uses the power light for data output as he is concerned about his captors gaining screen output via Van Eck phreaking (though this is unlikely; more likely they’d install some kind of bit-grabber between the keyboard and systemboard, or a resident Trojan).
However, here is something even cooler than an old computer with a big blinkenlight console. When I was in school I worked in one of the oldest buildings on campus and we went up to the attic one day to pull out some tables only to find something like this (but smaller) under covers. Unfortunately, we didn’t have a plotter, but someone managed to connect it to ADC board and we got it cleaned up and working with a drill motor powering it. Nerdy-cool stuff; we plotted ballistic traces and computed compound decay rates with it until somebody got wise and took it “for the museum” that was never built.