At first, Apple only focused on personal computer. They kept on developing hardware and software for their Apple computer. As a company, of course all design references from previous development became the continuation for their next products. And all derivative of computer and software as you can see now is derivative from all product that has created by Apple.
So does with iPhone when it was made for the first time, its hardware and software design reference refers to the previous hardware and software development. It was shocking when Steve Jobs told the world that iPhone is running Mac OS X in which it’s OS for their Mac series. When hold it for the first time, as if we were holding Mac which is miniaturized into a smartphone with a very well technology.
Now, Their new product, Apple Watch is not separated from previous Apple’s hardware and software. Its chance to be connected or compatible with other Apple products is big. Do you want a prove? Well, a developer names Nick Lee has demonstrated Mac OS 7.5.5 running on the Apple Watch in a video posted to YouTube. Lee was able to get System 7.5.5 running on watchOS 2 using the Mini vMac Macintosh emulator. System 7.5.5 was released back in 1996 and it ran on a bulky Power Macintosh 5500. Even though he only used an emulator but indirectly we can see Apple history in their current device.
The other interesting stuff is: Apple makes a great hardware and they are very good in term of miniaturization. When we saw Apple Watch, we seemed to see a miniaturized iPhone with perfect design and technology. Here’s the video Apple Watch runs Mac OS 7.5.5