The world of personal computing is changing as smaller, sleeker and more capable devices are replacing the bulky desktop towers and heavy laptops that formerly dominated the market. New data from Asymco shows just how profound the shift has been, finding that half of all computing devices sold in the U.S. are now mobile devices such as tablets or smartphones.

GigaOM has the story, which shows a graphic created by Asymco’s Horace Dediu that shows computing platforms going back to 1975. The graphic suggests that devices running Windows begin to lose sales pretty drastically starting around the time of the release of Apple’s iPhone in 2007, with Android coming on strong soon after to put pressure on both traditional computers and Apple’s computing devices.

Another bit of data GigaOM cites in its story comes from Gartner, which found that some 352.8 million PCs were sold in 2011, while  Samsung on its own sold 300 million Android handsets, and is estimated to be able to sell another 372 million in 2012. They won’t all be smartphones, but those devices will all be mobile, with the capability of accessing the Internet on-the-go and running mobile apps to accomplish various tasks. Their rampant popularity around the world suggests that many people are finding they don’t need a dedicated PC for many of their daily computing tasks anymore. At the very least, they’re finding mobile devices are a convenient way to share the load and bring the Internet out into the world with them.

More and more apps and devices are helping to bring the PC experience to tablets and mobile devices, as well. Streaming video game service OnLive recently released an Android app that allows users to stream PC games over the Internet to play on their Android tablets, which works surprisingly well and brings quality video gaming to mobile devices. The service just released an app for Apple’s iOS platform that allows not only for access of your PC desktop on an iPad, but allows users to run programs like Microsoft Word, watch videos and animations and even play PC games remotely on their tablets. The app is called OnLive Desktop and is making its way to Android sometime in the future as well.

Of course, PCs still have a big place in the computing world – they’re key for high-power functions that tablets and smartphones just don’t have the hardware to handle. But for the lower-level stuff, the everyday life functions that used to be handled by our laptops and desktops, mobile devices are quickly asserting themselves. The numbers suggest that the landscape is changing, and before too long, the way we interact with computers on an everyday basis will probably be very different than it is today.