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  The prize, financed by Intel and Google, is given by the Association for Computing Machinery, the world's oldest educational and scientific computing society, founded in 1947.

The Alto was the brainchild of Alan Kay, a young computer scientist who had studied at the University of Utah and taught briefly at Stanford University. Dr. Kay and his researchers had been early to foresee that computers would become more than digital calculators, evolving into a medium capable of blending sound, digital video and information. Dr. Kay referred to the resulting computer as an ''interim Dynabook.'' It was about the size of a mini-fridge and sat by the side of an office desk. Dr. Kay had closely followed the work of Douglas Engelbart, a computer pioneer, so the Alto was equipped with a pointing device -- a three-button mouse -- to move the cursor on the screen. Two experimental generations of the Alto were produced in the 1970's, and a prototype was installed at the White House. Ultimately, however, Xerox decided not to commercialize the Alto. Instead, in 1981, it unveiled the Star 8010 Information System, which never found a broad market because of its cost.

That isn't all.

But betting that past computer-tablet stumbles like AT&T's Eo and Apple Computer's Newton were simply ideas too far ahead of their technological times, Microsoft has bolstered its team with two legendary computer innovators, Butler Lampson and Chuck Thacker. One PARC concept from that era that has yet to bear commercial fruit, however, is the tablet computer, though no one is blaming Mr. Lampson and Mr. Thacker. Mr. Thacker, 56, and Mr. Lampson, 55, were part of a group, led by the computer scientist Alan Kay, that set out in 1971 to build a portable computing machine they called a Dynabook that would enable a user to stay wirelessly connected to a world of information. As graduate student at the University of Utah, Mr. Kay had written his doctoral thesis about such a machine, which he then called the Sketchpad.