“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.
Seattle-based Vulcan Inc., Allen's company for his network of organizations and initiatives, also released a statement on Allen's passing.
"Millions of people were touched by his generosity, his persistence in pursuit of a better world, and his drive to accomplish as much as he could with the time and resources at his disposal," Vulcan CEO Bill Hilf said.
“Paul’s life was diverse and lived with gusto. It reflected his myriad interests in technology, music and the arts, biosciences and artificial intelligence, conservation and in the power of shared experience – in a stadium or a neighborhood – to transform individual lives and whole communities,” Hilf said.
Allen, in a final social media post, had a message for the world.
“As long as we work together - with both urgency and determination - there are no limits to what we can achieve,” he posted.
Funeral arrangements have not been announced yet.
Original story: Microsoft co-founder and business entrepreneur Paul Allen's cancer has returned.
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Allen announced on social media Monday that the non-Hodgkin’s lymphoma he was diagnosed with in 2009 - and that he beat - has returned.
“I’ve begun treatment and my doctors are optimistic that I will see a good result,” Allen said in a post on Twitter.
Allen, one of the wealthiest people in the U.S., with a fortune estimated at $20 billion, according to his biography, was first diagnosed with non-Hodgkin's lymphoma in 1983, which prompted him to resign from Microsoft to battle the disease.
He first met Bill Gates when Gates was 12 and he was 14 when the two went to the same school in Seattle. By 1975, the two college dropouts founded Microsoft together.
Non-Hodgkin's lymphoma, or NHL, is a cancer of the white blood cells, which help the body fight off infection, and usually starts in the lymph nodes or other lymph tissue, according to the American Cancer Society. It mostly affects adults, but children can get it, too.