"As co-founder of Microsoft, in his own quiet and persistent way, he created magical products, experiences and institutions, and in doing so, he changed the world", Nadella said. The first bout forced him to leave Microsoft in 1982.
"Paul was a person who pushed so many intellectual envelopes and expanded human knowledge, and his legacy will live beyond bricks and mortar", Washington state Governor Jay Inslee tweeted Monday.
"He cared about the larger world, too, stepping up to fight Ebola and working to preserve endangered animals".
The company also released a statement on behalf of Allen's sister Jody.
"Paul loved Seattle and the Pacific Northwest".
Born in Seattle on January 21, 1953, Allen's love for football was first nurtured by his father, who took him to Washington Huskies games as a child. But the true impact of his vision and generosity is evident around the globe. Overall, Allen is estimated to have donated more than $2 billion to philanthropic causes. This isn't the time to deal in those specifics as we focus on Paul's family. Microsoft's big break came in 1980, when IBM Corp. chose to move to personal computers. IBM asked Microsoft to provide the operating system.
Allen, who left Microsoft in 1983, set up investment firm Vulcan Inc in 1986 to manage his multibillion-dollar portfolio.
Gates and Allen became billionaires when Microsoft was thrust onto the throne of technology.
In 1988, Allen purchased the Portland Trailblazers for $70 million, helping the team to develop the Moda Center where they now play, and seeing the team reach the playoffs 19 times under his ownership.
Allen was a pillar in the Seattle Sports scene after purchasing the Seattle Seahawks in 1996 and helping establish the Seattle Sounders in Major League Soccer back in 2007.
He was often seen at games or chatting in the locker room with players of the three teams.