According to Canalys, in the last quarter, Apple sold more computers worldwide than any other computer manufacturer, coming in at 21 million.
Don't take this too literally though; it turns out that Canalys considers any tablet with a 7" or bigger display as a PC, so Apple's strong iPad sales certainly helped. In fact for actual computers, ComputerWorld.com reports that Apple only sold 4 million Macs, which pales in comparison to the giants like Dell and HP who sold around 10 to 13 million PCs. But once you factor in 17 million iPads, Apple sold 21 million "computers."
Maybe its logical to consider tablets as PCs - after all, if you only want to browse the internet and watch some videos on your computer, if you purchase a tablet it'll do all that for you, so why would you buy a PC as well? This is the problem that plagues Microsoft at the moment - without a tablet OS (although one is coming) the company is losing sales due to the tablet market growth.
If we use Canalys view, we see that the PC industry has actually grown by 12% quarter for quarter (Q2 2011 vs Q2 2012). If we stick to a traditional viewpoint though, the market has actually gone down by 0.1%, quarter for quarter.