The notion of using some form of stylus or pen for interaction has been around since the earliest days of computing. Rewind back to 1957, there was the Styalator using a stylus for hand writing recognition. In 1964 the IBM 2250 was provided with a pen for vector graphics that was sensitive to light against a CRT monitor.
By 1987 Go Corporation was founded with a focus on pen computing, and consequently developed an operating system named PenPoint OS with this in mind. Intel invested in Go, causing angst at Microsoft for supporting a competing product.