Windows Mobile is a discontinued mobile operating system developed by Microsoft for smartphones and personal digital assistants (PDA). Designed to be the portable equivalent of the Windows desktop OS in the emerging mobile/portable area, the operating system is built on top of Windows CE (later known as Windows Embedded Compact) and was originally released as Pocket PC 2000.
Microsoft introduced the Pocket PC keyboard-less PDAs in 2000, with Pocket PC 2000 being the software. It was based on version 3.0 of Windows CE, the operating system originally developed for the Handheld PC in 1996. The next versions were Pocket PC 2002 and Smartphone 2002, the latter of which would power a new category of keypad-based cell phone devices named Smartphone. With the release of Windows Mobile 2003, the software was rebranded to a single "Windows Mobile" for both Pocket PCs and Smartphones, and to connect the brand with its desktop counterpart. Support for SH-3 and MIPS processor architectures were dropped, focusing only on ARM. In the next major release, Windows Mobile 5.0 in 2005, Microsoft unified the separate developments of Pocket PC and Smartphone software into a single Windows Mobile codebase. Data could be synchronized with desktops using ActiveSync software, and later using Windows Mobile Device Center.