Facebook Inc. is encouraging other companies to sell products and create software for use on the popular social networking site, hoping to expand into an all-purpose destination on the web.

The company's 23-year-old founder and chief executive, Mark Zuckerberg, said the move was similar to what Microsoft Corp. did decades ago, when the relatively obscure software maker began encouraging third-party companies to write programs for its personal computer operating system. The strategy made Microsoft phenomenally profitable and helped turn founder Bill Gates — like Zuckerberg, a Harvard University dropout — into the world's richest man.

"Until now, social networks have been closed platforms," Zuckerberg told about 750 programmers attending the company's first developer conference, dubbed f8. "We're going to end that."