Bill Gates has hopes a better condom will reduce HIV infections, is optimistic about digital currencies' ability to help the poor, and trusts he'll be able to help Microsoft in his new role as technology adviser.
Those were some of the topics covered by the Microsoft co-founder in a Reddit AMA question-and-answer chat session on February 10.
Gates' decision to participate in an AMA comes on the heels of Microsoft's announcement of its new CEO Satya Nadella. Microsoft didn't hold a press conference to discuss the appointment or make any executives available for interviews yet, so the Ask Me Anything session was the first time anyone from the company has answered questions from the public about the leadership change.
Asked about his new role at Microsoft, in which he'll be a technology product adviser, Gates said that he was "thrilled" that Nadella asked him "to pitch in" to ensure that Microsoft is "ambitious with its innovation."
"Even in Office there is a lot more than can be done," said Gates, who took on his new role while stepping down as board chairman.
He is particularly excited about how the cloud and new devices can help people communicate and collaborate in new ways.
"The OS won't just be on one device and the information won't just be files - it will be your history, including being able to review memories of things like kids growing up," said Gates, who later mentioned he's using a Surface 2 Pro, which "works well" for him.
He will also try to make sure Microsoft picks "ambitious scenarios and that we have a strong architecture to deliver on them" and that he will "hopefully" encourage good work.
Regarding Nadella, Gates said the new CEO is "off to a great start" and "taking a fresh view of where Microsoft is - strengths and weaknesses".
"A new person gets to step back and change the focus in some ways," he added.
His favourite projects at Microsoft were Windows and Office, which "defined the big success of the 1990s for Microsoft".
He said: "Office connected to the cloud has a LOT of potential and we are off to a good start. Cloud Storage needs to be a lot richer though."
Asked whether he views the PC as a "dead" device, Gates said that while the boundaries between different types of computing devices are blurring, there will still be a need for desktop computers, as well as for "wall devices".
"However, applications will be able to run across multiple devices including the whiteboard," he added.
Regarding the controversy over the US National Security Agency's practices of spying on individuals, Gates said there is a role for government in trying to gather information to stop crime and terrorism. "I do think terrorism with biological or nuclear weapons is something we want to minimise the chance of," he said.
However, the way the government goes about this "will have to be more open" so that people are able to trust the way the information is protected and gathered, he said.
Asked how he's different today from how he was in 1994, Gates said: "20 years ago I would stay in the office for days at a time and not think twice about it - so I had energy and naivete on my side. Now hopefully I am a bit more mellow but with a little extra wisdom."
Gates said that digital money that isn't anonymous - unlike Bitcoin - has the potential to help the poor because it has low transaction costs, and is thus viable for transactions involving small amounts of money. "Over the next five years I think digital money will catch on in India and parts of Africa and help the poorest a lot," he said.
Asked for an update on his foundation's efforts to promote the design of a better condom, Gates said the work is still in progress.
"This is a sensitive topic. The idea was that men don't like the current design so perhaps something they would be more open to would allow for less HIV transmission. We still haven't gotten the results. One grantee is using carbon nanotubes to reduce the thickness," he said.
Gates also fielded many questions about his philanthropic work with the Melinda & Bill Gates Foundation, saying at one point that "the greatest tragedy" is that of children who die in the developing world from preventable diseases or who never reach their potential due to malnutrition.
"We need vaccines and nutrition to solve this. We are making progress but not fast enough. Cynicism is the biggest barrier," he said.
He expressed optimism that polio can be eradicated worldwide soon and that in 20-30 years "gross inequity" will be almost eliminated, and along with it statistics such as the fact that a child in a poor country is 30 times more likely to die than a child in a middle income or rich country.
Literacy and nutrition are "basic things that we can afford to give to every child," he said.