NeXTSTEP
NeXTSTEP is a discontinued GUI (graphical user interface) operating system created by the NeXT company, founded in 1985 by Apple Computer co-founder Steve Jobs.
Although original interest was low, NeXTSTEP hosted the Electronic AppWrapper development, the early version of an app store. It was the first software distribution catalog to deal with encryption and digital rights for applications and digital media.
NeXTSTEP was also used as the foundation for the computer games Doom and Quake, and the first Internet browser created by Tim Berners-Lee.
Later, NeXTSTEP was used to help develop the OneStep API (application programming interface). After NeXT's acquisition by Apple on December 20, 1996, NeXTSTEP and OneStep were merged with Apple's user environment to create what would eventually become the macOS and iOS operating systems.