Apple Inc. said its new operating system for Mac computers will go on sale this Friday, a bit earlier than expected, as the company looks to continue to expand its share of the PC market.

Apple's new Snow Leopard software will sell as an upgrade for €20, starting on Friday.

Apple had previously said it would ship in September. Apple sold 2.6 million Mac computers in the June quarter, up four per cent from a year ago.

The company is the No. 4 PC maker in the US, according to research group Gartner, with 8.7 per cent of that market.

It does not rank in the top five in global shipments.

Apple rival Microsoft's new Windows 7 operating system is due in October.

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