Why two colors? A green ribbon was used when the user typed, and
  the black ribbon was used when the computer responded this was
  on typewriters I love learning stuff I didn't know about. I was
  researching the source of #linkedlist - a #concept I'm trying to
  really wrap my brain around thoroughly (not its limitations but
  why it's so powerful) - and I came across John Clifford Shaw,
  who invented the concept while doing the first
  #ArtificialIntelligence work. His team of three interviewed
  loads of people to try to understand "How Humans Think" and then
  get that into a computer somehow. Well, he went on to invent a
  language called #JOSS which is all but forgotten. JOSS was their
  attempt at creating a language so easy to use that YOU DIDN'T
  NEED A PROGRAMMER ANYMORE Well it worked too well. All the users
  started teaching other users how to use it. From Secretaries to
  big bosses had their typewriters hooked into the system, and
  they were happily chatting away with the computer. If the
  computer didn't understand you, it would simply say, "*Eh?*"
  Awesome stuff. Just... awesome stuff.?[1]JOSS_Session

References

  Visible links
  1. http://icopiedyou.com/wp-content/uploads/2015/07/JOSS_Session.jpg