Global shipments of "smart connected devices," including smartphones, tablets, PCs and notebooks, surpassed 1 billion units shipped last year according to a new report from IDC. The company said total unit shipments increased 29.1 percent over 2011 and that the estimated value of all devices shipped was more than  $576 billion.

PC unit shipments were down in 4.1 percent globally as tablet shipments increased 78.4 percent and smartphones unit shipments increased 46.1 percent. IDC said 128 million tablets were shipped in 2012.

Mobile phones tend to be the gateway drug in emerging markets where consumers typically move on to a tablet. "In emerging markets, consumer spending typically starts with mobile phones and, in many cases, moves to tablets before PCs," IDC research analyst Megha Saini, explained.. "The pressure on the PC market is significantly increasing and we can see longer replacement cycles coming into effect very soon and that, too, will put downward pressure on PC sales."

IDC says it expects global smart connected device unit shipments to surpass 2.2 billion units by 2017.