History and specifications
The Macintosh was first introduced in 1984, and was one of the first popular computers to use a graphical user interface.
Montgomery Scott encountered such a computer when he traveled back in time to 1986 from the late 23rd century. Tasked with enclosing a bay so that the crew of the late USS Enterprise could transport humpback whales to the 23rd century, Scott, Dr. McCoy, and Hikaru Sulu visited a company called Plexicorp. After a tour of the plant, Scott offered to show plant manager Dr. Marcus Walter Nichols a way of enclosing a water tank with a sheet only one inch thick, rather than six-inch sheets commonly in use at the time.
Nichols gave Scott access to his computer - which was a Macintosh Plus - to enter the formula for transparent aluminum. Scott at first didn't realize that the computer was from a time before computers had voice interfaces. When he was handed the mouse, he mistook it for a microphone, at which point Nichols told him to use the computer. Despite considering the keyboard to be quaint, Scott was able to use the computer to enter a formula for transparent aluminum. (TOS movie: Star Trek IV: The Voyage Home)