'Microsoft was everything': Bill Gates reveals how he changed careers after retirement

Bill Gates spent about three decades of his life building Microsoft, until he announced his retirement at 50. Soon, he switched tracks and made philanthropy and the Bill and Melinda Gates Foundation his primary focus. But for the billionaire, who was deeply and solely interested in one thing all his life - Microsoft, the career change was not easy.

But one habit helped.

“I had a long period from about age 18 to 40 where I was very monomaniacal ... Microsoft was everything,” Gates told comedian Trevor Noah on a recent episode of his podcast What Now? With Trevor Noah. “I was lucky enough that as other people took over Microsoft, I got to go and read and learn about all the health challenges, why children die.”

The 68-year-old Microsoft co-founder is known to be a voracious reader. And it was in 1997 - when he read an article about children across the globe dying of diseases that were easily cured in the US - that he made up his mind about what he would do once he stepped down as Microsoft CEO in 2000, CNBC Make It reported.