Microsoft co-founder Bill Gates marked his foray into the Twittering world on January 19, with his first message on the social networking site – on which posts are limited to 140 characters – being: “‘Hello World.’ Hard at work on my foundation letter — publishing on 1/25.”

In addition to joining the ranks of the Twitters, Gates has also rejoined the Facebook social networking site which he quit nearly six months back, after being flooded with thousands of “friend” requests.

To confirm that it is the real Bill Gates on the Twitter site, and not a celebrity imposter, the Twitter account of Microsoft’s part-time chairman - @BillGates – has been as being “verified.”

As the word about Gates joining Twitter spread, the number of his ‘followers’ touched over 60,000 on Day One itself!

One of the celebrity ‘firsts’ to extend a welcome to Gates on Twitter was actor Ashton Kutcher, who, last spring, became the first person on Twitter to boast over one million followers.

Gates’ response tweet to Kutcher read: “Thanks to you and all the other people who have welcomed me. I've got a lot to learn about Twitter but look forward to sharing more.”

After having stepped down as the Microsoft CEO in 2008, Gates is currently involved with the Bill and Melinda Gates Foundation, an altruistic endeavor that is dedicated to the improvement of health and education round the world.