Mobile application development requires use of specialized integrated development environments.
Mobile apps are first tested within the development environment using emulators and later subjected to field testing.
They began appearing in 2008 and are typically operated by the owner of the mobile operating system, such as the Apple App Store, Google Play, Windows Phone Store, and Black Berry App World.
However, there are independent app stores, such as Cydia, Get Jar and F-Droid. Usually, they are downloaded from the platform to a target device, but sometimes they can be downloaded to laptops or desktop computers.
User input allows for the users to manipulate a system, and device's output allows the system to indicate the effects of the users' manipulation.