NeXTSTEP

NeXTSTEP, also stylized as NEXTSTEP, is an object-oriented operating system that was developed by NeXT and introduced with the first NeXT Computer in 1988. Apple's modern macOS is derived from NeXTSTEP's Unix-based foundation.

History
NeXTSTEP adapted Display PostScript from Adobe Systems for use as its graphics engine. The integration of PostScript into the operating system allowed the NeXT Laser Printer and Color Printer to be significantly simpler and cheaper, while still maintaining speed and WYSIWYG accuracy in their printed output. It was also the platform on which Tim Berners-Lee designed the World Wide Web, and on which id Software developed the video games Doom and Quake.

On December 20, 1996, Apple Computer announced that it would acquire NeXT. An open-source version of the NeXTSTEP API called OpenStep was used to develop Mac OS X as Apple's next operating system, but it replaced Display PostScript with a new PDF-based imaging model called Quartz to avoid paying licensing fees to Adobe. iOS and macOS can trace their developmental roots to NeXTSTEP as their APIs are prefixed with NS (NSObject, NSString, etc.).