An app is a slang term for a software application or software programme that may be launched on a computer device to do a task; specifically, to perform it more easily and effectively than we could as mere humans.
MOBILE APPLICATION DEVELOPMENT
Mobile application development is the process of producing software for smartphones, most commonly for Android and iOS. One can preinstall, download, or use a mobile web browser to access the app
Software Re-engineering is a software development technique that aims to make a software system more maintainable. Re-engineering is the process of examining and altering a system in order to reassemble it in a new form.