Computer generated imaging, or CGI, was not born on a film set, but in research labs at universities, with the goal of making pictures from computer data. In the late 1970s, the early imaging technology was adopted by special effects teams at movie production companies, starting in earnest what we now recognize as CG effects.
The sci-fi western "Westworld" is credited with being the first movie to make use of 2-D CGI. Shots from the perspective of Yul Brenner's robotic cowboy were mind blowing at the time, but look a little silly now. That film opened the door for movies like "Tron" in 1982, the first film to make extensive use of CGI. A few years after "Tron" was made, director Barry Levinson had his digital team create the first CGI character in "Young Sherlock Holmes." From there, innovators like James Cameron, Steven Spielberg and the Pixar studio revolutionized CGI in movies like "The Terminator," "Jurassic Park" and "Toy Story." Today, you'd be hard pressed to find a mainstream movie released by a major studio that doesn't have some kind of CG effect.