What familiar device was invented by human-computer interface engineer Douglas Engelbart, creator of hypertext?
Purple Numbers Purple Numbers is a suite of tools that allows one to address paragraphs of HTML content. It was originally conceived by Douglas Engelbart for his creation of hypertext. The name comes from the faint, purple numbers at the end of each paragraph, which represent the link to that paragraph. The name was coined by Christina Engelbart, Doug's daughter.
Human interface device A human interface device or HID is a type of computer device usually used by humans and takes input and gives output to humans.