While visiting Plexicorp in 1986, Scotty had the opportunity to use a Macintosh. Although initially baffled by the lack of a voice interface – he mistook the computer mouse for a microphone – Scotty proved himself quite proficient in operating its "quaint" keyboard interface. (Star Trek IV: The Voyage Home)
Apple Computer Company – the full name of Apple in 1986 – is one of the few manufacturers to be the beneficiary of product placement in a Trek production. Kirk Thatcher suggested that the computer be a Macintosh. 
In 1992-93, Apple launched a project to port the Mac OS to run on Intel-based processors. The project's code name was "Star Trek", because the operating system would be going "where no Mac had gone before".
The production staff of the modern Star Trek series have frequently used Macintosh computers for both writing and artwork projects, including the Star Trek Encyclopedia and the Star Trek: The Next Generation Technical Manual.
- Apple Inc. at Wikipedia
- Macintosh at Wikipedia
- Macintosh Plus at Apple-History.com - stats and info page about the Macintosh Plus, the model seen in The Voyage Home
- A Visit to the Enterprise Set at TrekNation - a guided tour of the Enterprise set, mentioning the behind-the-scenes computers and software setup