Dealers of Lightning: Xerox PARC and the Dawn of the Computer Age

by Michael A. Hiltzik

The answer, unfortunately, was that the Alto’s 8½-by-11-inch screen encompassed just so much physical real estate—the space of a single sheet of writing paper. That limitation, as it happened, led directly to one of their most important contributions to the look of the computer screen—the concept of overlapping windows. The idea began by thinking of the screen in terms of a physical desktop. People in offices got around the same problem of too much paper and not enough room, Kay reasoned, by piling pages on top of one another. The analogous procedure would be to pile up small images on the screen—perhaps in some way that allowed the user to keep track of how many sheets, or projects, or windows, were open at once and to summon the most important one instantly to the top of the pile.