Computer technology has made incredible progress in the past half century. In 1945, there were no stored-program computers. Today, a few thousand dollars will purchase a personal computer that has more performance, more main memo- ry, and more disk storage than a computer bought in 1965 for $1 million. This rapid rate of improvement has come both from advances in the technology used to build computers and from innovation in computer design. While technological improvements have been fairly steady, progress arising from better computer architectures has been much less consistent. During the first 25 years of elec- tronic computers, both forces made a major contribution; but beginning in about 1970, computer designers became largely dependent upon integrated circuit tech- nology. During the 1970s, performance continued to improve at about 25% to 30% per year for the mainframes and minicomputers that dominated the industry. The late 1970s saw the emergence of the microprocessor. The ability of the microprocessor to ride the improvements in integrated circuit technology more closely than the less integrated mainframes and minicomputers led to a higher rate of improvement—roughly 35% growth per year in performance.
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