William Henry Gates III is born in Seattle, Washington, to William H. Gates Sr., a lawyer, and Mary Maxwell Gates, a businesswoman and philanthropist. He is the second of three children.

Gates demonstrates a keen intellect and a voracious appetite for reading from a young age. He excels academically but also exhibits a rebellious streak.

Enrolls at Lakeside School, a private school in Seattle. The school's Teletype Model 33 ASR terminal and a timesharing system connected to a General Electric computer spark Gates's fascination with computers. He learns BASIC programming with Paul Allen.

Gates and Allen begin programming together, debugging and improving the school's payroll system. They also develop a program to schedule students in classes.

Gates and Allen form Traf-O-Data, a company that analyzes traffic data for cities. The project is moderately successful and provides valuable entrepreneurial experience.

Scores 1590 out of 1600 on the SAT and enrolls at Harvard University, initially intending to study law. However, he spends much of his time using the university's computers.

While at Harvard, Gates and Allen read about the Altair 8800, the first commercially successful personal computer. They contact MITS, the maker of the Altair, and offer to develop a BASIC interpreter for it. They successfully demonstrate the software, leading to a contract.