Bill Gates answered user questions on everything from the dispute between Apple and the FBI to quantum computing when he participated in his fourth Reddit AMA ("Ask Me Anything") on Tuesday.

The personal computing pioneer also took a trip down memory lane by recreating a pose from his high school yearbook for his verification photo in the chat. He tweeted it out to his 27.6 million followers:

Perhaps the most topical issue brought up during the chat was the encryption dispute between Apple and the FBI over access to data on a locked iPhone belonging to one of the San Bernardino terrorists. User Day_Rider asked Gates for his take on the dispute, and Gates replied:

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I think there needs to be a discussion about when the government should be able to gather information. What if we had never had wiretapping? Also the government needs to talk openly about safeguards. Right now a lot of people don't think the government has the right checks to make sure information is only used in criminal situations. So this case will be viewed as the start of a discussion. I think very few people take the extreme view that the government should be blind to financial and communication data but very few people think giving the government carte blanche without safeguards makes sense. A lot of countries like the UK and France are also going through this debate. For tech companies there needs to be some consistency including how governments work with each other. The sooner we modernize the laws the better.

When another user followed up by asking what Gates would do if he were Apple, the former Microsoft CEO wrote that the company "could propose an overall plan for striking the balance" between the government's need to investigate and protect against future threats on the one hand, and the need to have safeguards in place "to make sure powers are confined to appropriate cases."

"There is no avoiding this debate and they could contribute to how the balance should be struck," he added.

The chat was wide-ranging. When one user asked if quantum computing, which involves harnessing the laws of quantum mechanics to process information faster, will catch on, Gates stated that he was unsure when or if it would "become mainstream." He did add that "there is a chance" that cloud computing will offer "super-computation by using quantum " within the next six to 10 years.

The AMA also touched on the question of artificial intelligence and whether Gates agreed with the likes of Elon Musk and Stephen Hawking that A.I. should be regulated "before it is too late."

"I haven't seen any concrete proposal on how you would do the regulation," Gates wrote. "I think it is worth discussing because I share the view of Musk and Hawking that when a few people control a platform with extreme intelligence it creates dangers in terms of power and eventually control."

Not every question was serious. One user asked Gates -- the richest man on the planet, according to Forbes -- if he would pick up $40,000 if he found it on the sidewalk.

But Gates gave a serious answer. "Since our Foundation can basically save a life for every $1,000 we spend I would pick it up since that would be enough to save 40 lives which is a big deal," he replied.

For a man who has long been at the forefront of technology, one of the more interesting questions posed whether there was a technological advancement from the past few years that Gates felt we would be "better off without."

"I am concerned about biological tools that could be used by a bioterrorist. However the same tools can be used for good things as well," Gates said. And he added: "Some people think Hoverboards were bad because they caught on fire. I never got to try one."