Picking up the pen required fumbling around on the table or, if it had a holder, taking the time after making a selection to put it back. To do the pointing, the user’s arm had to be lifted up from the table, and after a while that got tiring. The light pens used to select areas of the screen by interactive computer systems of the 1950s and 1960s-including Sketchpad-had drawbacks. Many other engineers, however, see Sketchpad’s design and algorithms as a primary influence on an entire generation of research into user interfaces. Running on MIT’s TX-2 mainframe, it demanded too much computing power to be practical for individual use. Though films of Sketchpad in operation were widely shown in the computer research community, Sutherland says today that there was little immediate fallout from the project. The program must calculate where a line is to be drawn, compare that position to the coordinates of the window in use, and prevent the display of any line segment whose coordinates fall outside the window. Clipping is a software routine that calculates which part of a graphic object is to be displayed and displays only that part on the screen. Moreover, to zoom in on objects, Sutherland wrote the first window-drawing program, which required him to come up with the first clipping algorithm. Sketchpad, created in 1962 by Ivan Sutherland at Massachusetts Institute of Technology’s Lincoln Laboratory in Lexington, is considered the first computer with a windowing interface. Suits now being litigated could assign those innovations not to the designers and their companies, but to those who first filed for legal protection on them. The Mac’s success during the 1980s spurred Apple Computer to pursue legal action over ownership of many features of the graphical user interface. By now, application programmers are becoming familiar with the idea of manipulating graphic objects. During the next five years, the price of RAM chips fell enough to accommodate the huge memory demands of bit-mapped graphics, and the Mac was followed by dozens of similar interfaces for PCs and workstations of all kinds. In 1984, the low-cost Macintosh from Apple Computer Inc., Cupertino, Calif., brought the friendly interface to thousands of personal computer users. From the Alto’s concepts, starting in 1975, Xerox’s System Development Department then developed the Star and introduced it in 1981-the first such user-friendly machine sold to the public. More than 1200 Altos were built and tested. In 1973, PARC developed the prototype Alto, the first of two computers that would prove seminal in this area. Throughout the 1970s and early 1980s, many of the early concepts for windows, menus, icons, and mice were arduously researched at Xerox Corp.’s Palo Alto Research Center (PARC), Palo Alto, Calif.
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