Wallace worked at the Retail Computer Store in Seattle, where he learned about Microsoft after Bill Gates put up a sign advertising for programmers. He joined Microsoft in 1978 as the 9th employee. His first project was to connect a computer to an IBM Selectric typewriter so the company could print software manuals. He was a key developer of TI BASIC. In the late 1970s, Wallace and Gates were known for their hijinks, and one incident involved breaking into a construction site and driving bulldozers, at one point almost running over Gates's Porsche.