The Computer Interface


One of the ways that people tend to think about interfaces is ways of getting discrete and accurate information into the computer because computers process numbers. Input interfaces are ways of converting the real world into numbers(digitizing), but the world is continuous not discrete. Going back to the idea that interactive works can be put on a spectrum from controllable to responsive, interfaces can be put on a similar spectrum with command on one end and measurement on the other and these usually correspond to discrete interfaces on the command end and continuous on the measurement end. And again where an interface fits on this spectrum has not just to do with its implementation but also with its perceived structure.

A few examples: A foot switch is mounted under a carpet near a video monitor. If the viewer walks up to the monitor and steps on the carpet the switch is closed and triggers an image and sound to start playing on the monitor. When the viewer leaves the carpet the image and sound stop. If the viewer wants to see the image again they step on the carpet. It's a command to start the image. The viewer is not interacting with the image or what's behind it, the program, they are interacting with the foot switch. There is no dialogue. It's a discrete interface, like an icon, the switch is on or off, the image is on or off.

A second example: 100 foot switches are mounted in a row under a carpet to create a position detector that measures a viewer's distance from the same video monitor as above . The system can differentiate 100 possible distances from 0 feet to 20 feet. The image is at maximum brightest and the sound is at maximum volume when the viewer is 20 feet away, but as the viewer walks closer the image and sound fade to nothing reaching nothing when the viewer is 1 foot away. A viewer will find that the optimal positions for image intelligibility and sound intelligibility will be different.

Different viewers might respond in any of a number of ways from oscillating between these 2 optimal positions to compromising to prioritizing, but an important point is that their action will be based on what they are seeing and hearing, not on where their feet are. This illustrates the fundamental difference between discrete interfaces and continuous ones, namely that in discrete interfaces the interaction is between the viewer and the interface and in continuous interfaces the interaction is between the viewer and the work or the program.

Even though the interface is discrete as all digital representations by definition are, it will be perceived of as being continuous because the difference between any 2 of the 100 levels is imperceptible... Of course one could display the distance as a number between 1 and 100 on the screen along with the image and this would turn the perceived continuous interface into a discrete one causing the viewer to interact with the number, like a slider bar on a mac or windows program.

Interfaces that involve discrete choices leave little room for intuition. Discrete choices generally cause the viewers to look for a logical reason to make the correct choice based on what they might think the consequences will be. Unless it's a game there is no correct choice.


It has been my experience that intuitive interaction through an interface can only be possible if that interface is able to understand any input of its type.

A couple of examples: If the interface to the computer is word recognition , then the computer should have a reasonable understanding of anything that might be said to it, not just a few words. I

If the interface to the computer is a distance measuring device then the computer should understand distance in any direction that it is approached from, not just from straight on.

If an interface has holes in it with regard to its structure, then it will be disregarded by a viewer simply as metaphorical and any interaction that does occur between a viewer and the work will get stuck at the interface.

The interaction that occurs will be between the viewer and the interface not between the viewer and the work or the program, just as I suggested earlier with discrete interfaces.

A transparent interface is a continuous one that is perceivably complete over its type of structure.