Scotty uses the Mac to explain the formulation of transparent aluminium. He first attempts to talk to the computer through the mouse.
Things seem to happen unnaturally quickly, but the actual ouput looks reasonable for a Mac of this era.
Year of feature (shown above)
Actually, I'm more convinced that the output on the screen is inlaid, and is based on Apple II screens that were created with MousePaint // - and each key press just advances the slideshow by a frame. That the actual computer doing the job is an Apple II, as the pixels are simply too big for the Mac screen. The desktop environment actually looks more Lisa OS like, too. Which is how the Apple II version of the paint program would resemble due to the Lisa and Apple II having rectangular pixels, and the Mac having square pixels. The "slideshow" also ends with an Apple II beep.
I don’t recall if this actually showed up in the movie or not? I recall seeing a still photo of that scene in a magazine at the time (may have been in MacWorld, MacUser, or A+?). It was a shot through the window from the hallway outside the office, that showed the back of the computer. There was no power cord plugged into that Mac Plus. Also there was a round hole in the case with a cable going through it that was feeding in the phony video.