The software, which Gates predicted would be widespread by the end of this decade, would also be smart enough to let users know if and when it should alert them--and on which device--with new information such as weather forecasts or sports scores.
He dismissed predictions that mobile phones one day would replace PCs as they evolve into data-processing devices.
"Some people have talked about the idea that 'Isn't there competition between the PC and the phone?' To me this is absolutely wrong," Gates told a room packed with consultants, other business people, and politicians in downtown Vienna.
"If you want to write a document, if you want fill out your tax returns, you'll use the larger screen device. If you want to go out and just take something that fits in your pocket, you'll take the phone," he said. "And so there's an imperative to make these things work together."
"For example, if you want to be notified about something that's changing, that's important to you, software should know which device you have with you and should know what you're doing, know the context to understand if interrupting you with this new information is appropriate or not," Gates said.
Gates, the richest man in the world, spoke as European Union antitrust regulators prepare to crack down on Microsoft Corp. The software giant is negotiating with the EU in an attempt to avoid extensive changes to its business practices.
The EU charges that Microsoft is unfairly harming competitors by "bundling" its Media Player software with its dominant Windows operating system, and that the company is not providing enough information to rivals in the market for low-end servers.