Windows Phone 7
Microsoft's hardware requirements stipulate that every device running Windows Phone 7 must have a dedicated Search button on the front of the device that performs different actions. Pressing the search button while an application is open allows users to search within applications that take advantage of this feature; for example, pressing Search in the People hub lets users search their contact list for specific people. This has been changed in Windows Phone 7.5 however – as the search button is reserved for Bing – so applications that previously used this feature (such as the Marketplace) now include soft search buttons.