Interface expert Jef Raskin came out strongly against modes, writing, "Modes are a significant source of errors, confusion, unnecessary restrictions, and complexity in interfaces." Later he notes, " 'It is no accident that swearing is denoted by #&%!#$&,' writes my colleague, Dr. James Winter; it is 'what a typewriter used to do when you typed numbers when the Caps Lock was engaged'." Raskin dedicated his book "The Humane Interface" to describe the principles of a modeless interface for computers. Those principles were implemented in the Canon Cat and Archy systems.