After building a software empire with businesses across the globe, Gates now plans to devote his entire time to philanthropic activities.

He intends to spend more time on his global health and education initiatives at the Bill & Melinda Gates Foundation.

So what is the world's best known geek like? What is it like to work with him and to interact with him?

Redmond, US-based S Somasegar, senior vice president, Microsoft, shares his experiences of having worked closely with Bill Gates:

I feel fortunate to have interacted with Bill Gates for the last 15-plus years. He is truly a remarkable person. I have found that there are quite a few people who are super-smart from a technology perspective and there are those who are super-smart from a business perspective. Very rarely do you come across a person who can take on both roles and be excellent in both.

Bill, I think, is one such guy and I have learned a lot in working with him.

The first time I had the opportunity to meet face-to-face with Bill, he was presenting me with an Achievement Award back in 1993. He presented the award to me pronouncing my full name. Most would not attempt it, let alone get it right. As he wished me congratulations, he whispered to me and asked whether he had pronounced my name correctly. That left a lasting impression on me.

Another key moment for me in working with Bill was after he visited India in March 1997. Bill returned from that trip very impressed with the people he had met, both by their education and passion for IT.

He came back and sent an email to the senior executives at the company about the opportunity he saw there -- the opportunity to engage more of the best and brightest software technologists in the world. He had big dreams for the company and knew we needed to tap into the talent from around the world to achieve those goals.

It was then that I was given the mission to build an R&D centre in India. We started the centre with 8 employees and today we have about 1,500 people contributing to our innovative product portfolio across Microsoft.

As I continued to engage with Bill over the years I have been continually impressed with the depth of his technical knowledge given the breadth of the Microsoft portfolio. He had the ability to deeply dive into meaningful conversations with the most senior architects and technical managers and focus on areas of weakness or opportunity, fully comprehending the deepest layers of our system architecture.

These days, he acknowledges, there are some pieces of our technology where he does not have the background to go to this layer of depth, but I remain surprised even today, at his level of engagement and knowledge in our technical strategy and offerings and how they all fit together.

The vision that he has for how technology can evolve and how software can play a crucial role in that is something that everybody knows. Many people are aware of this technical ability that Bill possesses, but something that may be less well known is his passionate interest in supporting our customers.

Just a couple weeks ago I was reminded of this. We were backstage prior to a keynote at our recent TechEd Developer Conference and, of all the things we could be discussing minutes before the speech, Bill was focussed on having a discussion with us about some planning we are doing for the next version of Visual Studio.

He had some strong opinions on work we need to do to make sure we are taking care of our customers. This is consistent with many discussions we have had and he is always very aware of how our customers are using our technology and their needs -- this is definitely something that has driven him along with his passion for technology.

Sharing the stage with Bill at our TechEd developer conference on June 3, 2008, his last keynote while still a full-time employee of Microsoft, was quite memorable for me. It was great to see that his last talk was for a developer audience given that has been a focus for him since the inception of the company.

When Microsoft was founded back in 1975, we were working on a BASIC interpreter for the Altair 8800 targetted at developers. Since then, we have always been a platform company at heart and Bill has consistently driven the importance of delivering a rich and broad platform that enables developers to build great experiences and applications and be successful in the process.

At TechEd, I saw that come a full circle as he talked about the latest wave of innovation we are delivering to developers today and (will do) in the future. At this same event, I hosted a group of influential technical community members to chat with Bill Gates over lunch who were all selected because of the great work they do in supporting others in the community.

I left feeling somewhat overwhelmed by the passion that people in the room had for a single topic that took up the majority of the conversation. The conversation centered on how we can better marry IT skills and expertise to non-profit work in the areas of healthcare and education. All of the conversations and comments focussed on how each of the people in that room could step up and bring their expertise in technology and IT to help people that are less fortunate.

I love the fact that the influentials that support our Microsoft developer community are also passionate about supporting the needs of the less fortunate.

Something that Bill said during this lunch really struck a chord for me. He said: "It is great how much people open their hearts, minds and wallets and dedicate their time when a tragedy strikes. However, the work that has an even greater impact is the work that is done a year or two years before a crisis that puts a framework in place so a response can happen more quickly."

This isn't something that we all think about in our daily lives until we are bombarded with news of a tragedy.

As I said, I left this meeting feeling inspired. Bill has achieved outstanding success with Microsoft. He has had a tremendous impact on the IT industry and on how we use technology in our daily lives. Now as he embarks full-time on his mission at the Bill and Melinda Gates Foundation, I think he has an opportunity to have an equal or greater impact and that leaves me hopeful.

I am confident that Bill will have a very broad impact around the world with the work that he is undertaking as part of his Foundation.

It has been a privilege to work with Bill and I look forward to carrying on his principles of supporting our developer community and driving technical innovation.

Image: Microsoft Chairman Bill Gates with S Somasegar, senior vice president, Microsoft Corporation. Photograph, courtesy: Microsoft