Bill Gates says he regretted leaving Harvard to lead Microsoft as its first CEO

Bill Gates served as Microsoft CEO until stepping down in 2000.

Bill Gates was 20 when he left Harvard University to run Microsoft as its first CEO in 1975. Now, the billionaire has come forward to say that he regretted quitting college especially when he had such “a great time”.

In his new memoir, Source Code, Gates said that even after he left, he wanted to return to Harvard to complete his degree. He added that he loved the university's intellectually rigorous atmosphere, where he could learn about a wide array of topics in depth.

"I enjoyed Harvard. I enjoyed the classes, including some that I just sat in on: psychology, economics, history courses. I loved having smart people around. We could sit and talk late into the night about very interesting things," he told CNBC Make It.

Gates was, however, pushed into making a choice after a technological development offered an opportunity that Gates and his Microsoft co-founder and high school friend Paul Allen had to seize, or someone would have beaten them to the punch.

In high school, Gates and Allen knew that microprocessors — small computer chips — would eventually help turn big, bulky, and expensive computers into small and affordable machines accessible to the masses. But they thought the technology was not ready yet. In 1974, however, Allen “burst" into Gates's room carrying the latest issue of Popular Electronics whose cover story was on the “world’s first minicomputer kit to rival commercial models”--a computer made by Micro Instrumentation and Telemetry Systems (MITS) called the Altair 8800.

At the time, both Allen and Gates believed that if they could create a software for the computers, they could be at the forefront of a new industry. They also knew that if they had to act quickly.

So for the next two years, Gates tried to balance running Microsoft while studying and even tried to convince another high school friend and early Microsoft programmer Ric Weiland to “take charge of things,” so he could complete his degree. But Weiland left for graduation school and Gates had no one else to lean on. “Even Ric wasn’t going to pull things together with the intensity that I knew we needed to stay in front,” he told the publication. "I had to give in to the inevitable, and give up school and, of course, never go back."

So Gates retained the reins of Microsoft CEO until stepping down in 2000. During his tenure, the company revolutionised the computer industry and turned Gates and Allen into billionaires. Currently, Microsoft is worth more than $3 trillion, CNBC reported.

Gates's former applied mathematics professor Harry Lewis also came on record earlier this year to say that too had a regret. “I wasn’t surprised when he dropped out," Lwesi said. "I just wish I’d invested in him.”

The former professor, who has taught at Harvard since the 1970s, told The Times of London that he remembered Gates as being “mature” beyond his years. The 20-year-old also had a tendency to question adults and tackle difficult problems. “He always wanted a challenge,” Lewis said.