In an interview with CNBC’s Make It published on Wednesday, the tech billionaire revealed that his definition of success included his software and its global impact.

“Back then, it was just: Is my code really good? Does it work? And can this company show the world that these microcomputers are big?” Gates said.

His view also spoke to his evangelism about the potential of personal computers to transform business and society. While the PC’s impact is clear now, it wasn’t obvious to everyone four decades ago, even to some of the early innovators.

In 1981, IBM launched its PC and famously estimated that it would only sell 241,683 units over a five-year period. Instead, it sold about 3 million in that time and hundreds of millions over a decade.

Of course, all those PCs needed software, and that’s where Gates saw an opportunity, applying a relentless single-mindedness to it.

“It was the magic of software,” he told CNBC. “And I was willing to focus my life, in my 20s, just on software, just on the one job.”

In fact, he and Microsoft cofounder Paul Allen had a vision of putting a PC on every desk and in every home, “which sounds boring today, but back then [it] was completely crazy,” Gates added.

Looking back on those early years, he characterized his view of success as “very much Microsoft-centric,” describing his life during his 20s as “all Microsoft, all the time.”

Gates stepped down as CEO in 2000, gave up his day-to-day duties in 2008, relinquished his chairmanship role in 2014, and left the board in 2020. Now focused on his philanthropy, he said his definition of success has evolved and includes “adding net value” to the world as well as empowering other people.

During a commencement address to Northern Arizona University’s graduating class in 2023, he expressed some regret for his approach to work in Microsoft’s early years, when he said he didn’t believe in weekends or vacations and pushed others to put in long hours.

“As I got older—and especially once I became a father—I realized that both in terms of doing your best work and having a great life, that that intensity was not always appropriate,” he said. “Don’t wait as long as I did to learn this lesson.”

But he still plans on staying busy, telling CNBC earlier that he intends to keep working for at least another two decades if his health allows—following in the footsteps of Berkshire Hathaway CEO Warren Buffett. That’s because retirement “sounds awful” to Gates.