Courtesy of David WeeklyA jack-of-all-tech-trades, Alan Kay lays claim to at least two watershed innovations, starting with HP's original Dynabook, one of the first usable mobile laptop computers. Kay ideal was to design a laptop that weighed no more than 2 pounds. We still aren't there yet, but Kay's contributions to software--which include shepherding the idea of object-oriented programming and the notion of multiple, overlapping windows in a GUI--rank as essential milestones in computing.
20. Marc Andreessen
Courtesy of Duncan DavidsonThe Mosaic Web browser devised by Marc Andreessen may seem quaint now, but bits and pieces of Mosaic code remain standard software components of most of today's commercial browsers. It's a safe bet that many of Andreessen's other creations will leave similar legacies: Netscape, the company he founded, set off the tech stock craze of the 1990s, and his Ning Web site continues to grow in popularity as an outlet where anyone can build a topic-oriented social network. He even finds time to blog regularly about all this stuff.
21. Linus Torvalds
Courtesy of Martin Streicher, Linuxmag.comGiven the exorbitant cost of most Apple computers, Linus Torvalds is the godfather of what may be the last, best hope for an affordable alternative to Windows. The Linux operating system has been in continuous development since Torvalds conceived it in 1991, and has experienced steady gains in popular acceptance every year. And a long last, Linux is making the jump from server rooms to large numbers of desktop PCs, most visibly in low-cost laptops like the Asus Eee PC. The OS now has a market share in excess of 2 percent on the desktop.
22. Chuck Thacker
Courtesy of MicrosoftChuck Thacker has had his hands in a surprisingly wide array of tech projects, from the development of ethernet to the first laser printers. His most enduring legacy, however, involves a product that never reached market: The fabled Xerox Alto. The Alto, which Thacker designed, was the first computer with a GUI (and a mouse); as the story goes, it directly inspired Apple to build the Macintosh after Steve Jobs paid a friendly visit to Xerox. Thacker now works for Microsoft.
23. Bob Metcalfe
Courtesy of Wikimedia CommonsMoore's Law may be better known, but the law formulated by Bob Metcalfe has wider general application. Posited around 1980, Metcalfe's Law conjectured that the value of a telecommunications network is equal to the square of the number of nodes on the network. In other words, even a small increase in the size of a network makes it worth far more because of the enlarged number of new connections that each user can make. Metcalfe's invention of ethernet and his founding of 3Com are essential tech milestones as well, but his eponymous law--now in use to quantify value in the Facebook/MySpace milieu--will be around long after wired networking has passed on.
24. Vic Hayes