Doug Engelbart, edge notched cards, and early links

Hypertext is intimately connected to the computer. These two technologies almost seem like they were made for each other Hypertext can be characterized as a random access medium, it offers us a way to form non-sequential connections between ideas. Digital computers, in their modern incarnation, offer superb tools for randomly accessing data. This pairing works well, but it's not the only way to implement a hypertext or hypertext-like system. Edge notched cards, although obscure today, represent an example of hypertext existing separate from digital machines.

This October will be the 60th anniversary of the publication of Doug Engelbart's Augmenting Human Intellect [1]. The eventual product of this research, NLS [2], was a highly influential computerized hypertext system. However, the path towards augmentation started outside the traditional digital realm. Within Augmenting Human Intellect Engelbart describes how he kept a series of linked notes using edge notched cards. These cards are simple pieces of paper with a pattern of notches and holes along their edges.

Edge notched cards were developed alongside punch cards as a means to categorize data. The edges of these cards are used to encode metadata about the contents of their faces. The pattern of holes and notches around each card's perimeter allows specific cards to be pulled from a mixed and unsorted deck. This is accomplished by threading a large needle through a specific hole. Once needled all you have to do is pull up; any cards with a notch in that position will fall out of the deck. This allows users to select specific data from a pack of hundreds of unsorted cards.

The notch card notes that Engelbart discusses in Augmenting Human Intellect are currently housed in the Engelbart Papers at Stanford's special collections. There are on the order of thousands of notch cards in this collection. Combining those notes and Engelbart's published description give us a reasonable understanding of how he was using edge notched cards in his own research. This gives us a window into a non-computer form of hypertext that was used at a crucial time in the field's development. In this set of notes we can see examples of links, tagged metadata, and stitching - all familiar features of hypertext systems.

This keynote will discuss the specifics of this physical form of hypertext. I will show how links as implemented on edge notched cards compare to computer hypertext systems, how this simple technology connects to historic hypertext systems, and what lessons can be learned by looking outside the digital context.