What computer accessory was the result of the work on human-computer interaction by the creator of hypertext?  
Purple Numbers: Purple Numbers is a suite of tools that allows one to address paragraphs of HTML content. Purple Numbers:  It was originally conceived by Douglas Engelbart for his creation of hypertext. Douglas Engelbart: Douglas Carl Engelbart (January 30, 1925 – July 2, 2013) was an American engineer and inventor, and an early computer and Internet pioneer.
i don't know