When was cenorship introduced into the computer?

It depends on what you mean by censorship. You can write anything that you want on your computer. You can create anything that you can imagine... but you cannot expoit children. If your computer is not connected to the outside world, it's pretty much up to you what you do with it. As soon as you connect to others, Communication laws are in effect which limits what can and cannot be sent across public communication media. Communication laws have been in effect pretty much since the early history of the telephone.