There are many types of Smartphone operating systems available, including: Symbian, Android, Blackberry, Palm Pre, Apple iOS, Windows Mobile Professional (touch screen), and Windows Mobile Standard (non-touch screen).
Among the most popular are the Apple iPhone, and the newest – Android. Android is a mobile operating system (OS) developed by Google. Android is the first completely open source mobile OS, meaning that it is free to any cell phone carrier. The Apple iPhone, which has several OSs like the 3G and 3G S, is the most popular smart phone at this time, because of its customizable OS which you can use to download applications made by Apple (often referred to simply as “Apps”) like games, GPS, Utilities, and other tools. Any user can also create their own Apps and publish them to Apple’s App Store.
The BlackBerry RIM is a SmartPhone that has a multimedia player and third-party software installation.
The Windows Mobile Professional Smartphones (Pocket PC or Windows Mobile PDA) are like that of a PDA and have touchscreen capabilities. The Windows Mobile Standard does not have a touch screen but uses a trackball, touchpad, rockers, etc.
Symbian is the original smartphone OS, with the richest history and the largest marketshare. Although no single Symbian device has sold as many units as the iPhone, Nokia and other manufacturers (currently including Sony Ericsson and Samsung, and previously Motorola) release a wide variety of Symbian models every year which gives Symbian the greatest marketshare.
J2ME or Java for mobile is the operating system which is used on feature phones (small low end phones like Nokia or Motorolia phones).
If you target a wide range of users, you need to create compatible versions of your applications with the above operating systems. For specific audience however, companies may only create and support oneversion of their application (e.g. BlackBerry for business users) or iPhone just for games built for its audience.