We'll start by looking at how NeXT got started, what they developed, why Apple bought them and then what Apple has done with the technology since the NeXT acquisition.
NeXT is born
Small, fresh companies have the luxury of clean drawing boards and are motivated to achieve great things merely to survive. After achieving success, those small nimble efforts more often than not morph into cubicles of corporate stagnation, where "achieving greatness" becomes a threat to sustained profitability.
Apple started out with an outrageous success in the Apple II, a product Apple still credits itself with in every press release for 'igniting the personal computer revolution in the 1970's.' As the Apple II line grew outdated, Apple struggled through a couple failures before again hitting upon success with the Macintosh in 1984. While the Mac continued to develop incrementally, many of those involved in Mac development at Apple moved on to other projects in search of the next new thing.
After cofounder Steve Jobs lost a power struggle within Apple in 1985, he left to pursue other interests as well. For the next two years, Jobs and several former Mac engineers laid out plans for developing the computing environment of the future. Initially called NeXT Inc., the group determined that no existing system was capable of running the tools they envisioned. They changed their name to NeXT Computer, and developed their own advanced hardware that in many ways built upon Apple's Mac. The software running NeXT, however, would be very different.
Rather than attempting to write an entire operating system from scratch, NeXT built upon a academic project called Mach. Since Mach was designed to only handle extremely low level functions, NeXT paired it with a 'user space' or personality of BSD Unix. Above that, NeXT developed a series of object oriented frameworks for developers, along with a graphic user environment that used the same PostScript display language popular in print imaging, ensuring that what was displayed on the screen was exactly what would be printed.
This OS package, called NeXTSTEP, built upon existing work and layered functionality into manageable tasks. Mach supplied the core machine functions and BSD Unix the middle OS functions, such as working with files and networking. This left NeXT to focus on refining their user interface and developing the frameworks to make development of NeXT software fast, easy and beautiful.
Part II > NeXT searches for a market