CALIFORNIA, USA:The number of mobile phone operating systems is on the rise, with Apple and Google the most notable entrants of late.

While Apple, BlackBerry maker Research in Motion and Palm develop their own operating systems just for themselves, the following systems battle for handset makers and consumers in the open market:

Symbian

Symbian leads the market for software platforms, but has lost much ground over the last year to Apple and RIM.

Nokia bought out other shareholders of Symbian last year and committed to give all its software to an independent foundation, which will develop it on an open-source basis.

The Symbian Foundation, which inherits intellectual property from Nokia and other former shareholders of UK-based smartphone maker Symbian, will distribute its first royalty-free software in April.

The foundation expects to have 400-700 members by the end of the year. So far, 78 companies have said they would join.

To date, about 250 million Symbian phones have shipped worldwide, a third of those in the last 12 to 18 months.

The world's largest smartphone maker Nokia uses only Symbian software, while Symbian is also the key platform for No 4 phone maker Sony Ericsson, which has said it will use also Windows and Android as complementary offerings.

Android

Google's Open Handset Alliance of companies supporting its Android mobile phone software currently has 47 members, including Taiwanese smartphone maker HTC, Germany's T-Mobile and Intel, the world's biggest chipmaker.

Many companies said last month at the wireless fair in Barcelona they planned to build Google phones, but only HTC -- with its new Magic phone that will be sold by Vodafone -- announced concrete plans.

All top cellphone vendors except Nokia have said they would use Android in their phones. No 5 Motorola, which has seen its market share dive in the last few years, has said Andoid will be the key in its future smartphone offering.

Windows mobile

Microsoft has tried to conquer the mobile market for years but without major success. Its Windows mobile operating system used to be the second most popular for smartphones after Symbian, has been overtaken by Apple and Research in Motion.

All top vendors except Nokia are supporting Windows, but HTC is currently the world's largest maker of phones using Windows software.

While Samsung Electronics, Motorola and Sony Ericsson have Windows phones on the market, they make up only a small proportion of their offerings.

Last month Microsoft signed a deal with LG Electronics, under which the world's third-largest cellphone maker will use Windows software in most of its smartphones.

Limo

Linux consortium LiMo hopes to benefit from its focus on giving greater say over software development to telecoms operators.

LiMo has been missing support from the largest cellphone vendors -- so far only NEC, Panasonic and Motorola have unveiled phones using its software. Samsung and LG are members of LiMo, but have not unveiled commercial models.

Last month its key members -- Vodafone, Orange, Japan's NTT DoCoMo, Korea's SK Telecom, U.S. operator Verizon Wireless and Telefonica -- pledged to introduce LiMo phones in 2009.