As they later told the story, Allen ran to Gates’ dorm room and persuaded him to help write a version of the programming language Basic for the Altair’s Intel chip, something some experts at the time said couldn’t be done. In a two-month marathon, they did it. On a flight to Albuquerque, where he hoped to sell the program to the Altair’s manufacturer, MITS, Allen realized that a key part of the code was missing. So he wrote it out on scraps of paper on the plane.

Source: Los Angeles Times October 15, 2018 22:12 UTC