One-third of computers sold worldwide in the fourth quarter of 2012 was a tablet, according to a survey released Wednesday.

The research firm Canalys said that with PCs and tablets combined, the market grew 12 percent year-on-year in the last three months to reach 134 million units.

With its iPads and other computers, Apple led the market with 27 million units, and a 20 percent market share.

That compared with 15 million for second-place Hewlett-Packard, which was just 200,000 units ahead of China-based Lenovo. Each had a share of 11 percent.

Samsung placed fourth with a nine percent share and 11.7 million computers and tablets, Canalys said.

Dell faded to fifth place with 9.7 million units, a 19 percent decline from a year earlier.

The report said just three percent of tablets shipped in the quarter used a Microsoft operating system despite the launch of the new Surface and other Windows-based tablets.

"The outlook for Windows RT appears bleak," said Canalys analyst Tim Coulling.

"We expect Microsoft to rethink its pricing strategy for RT in the coming weeks," he said, adding that getting manufacturers on board would probably mean "dropping the price by 60 percent."

The report said tablet sales were up 75 percent overall in the fourth quarter to 46.2 million units, bringing the full-year total to 114.6 million.

Canalys estimated that the new iPad mini made up more than half of Apple's tablet sales, and that Apple's overall share of the tablet segment fell to 49 percent, becoming the first quarter it has not controlled over half the market.

"Apple timed the launch of the iPad mini well," said Pin-Chen Tang of Canalys.

"Its success proves there is a clear demand for pads with smaller screens at a more affordable price. Without the launch, Apple would surely have lost more ground to its competitors."

Canalys said Amazon's worldwide shipments grew 18 percent in the quarter to 4.6 million units, as it expanded the Kindle Fire and launched in markets outside the United States.