Although【21】______ circuits made computers smaller, the processing units still consisted【2
Although 【21】______ circuits made computers smaller, the processing units still consisted 【22】______ a number of circuits on separate chips. In 1971, an engineer working for Intel realized that a 【23】______ of circuits commissioned for an electronic calculator could all be put 【24】______ one chip, and that the resulting device could be used 【25】______ a general-purpose "computer on a chip". The result was the Intel 4004 -- the world's first microprocessor. Physically, it consisted of a silicon chip in a protective ceramic capsule, with a set of metal pins sticking 【26】______ that connected it to other components in whatever 【27】______ it controlled. It 【28】______ 2,300 transistors, 【29】______ 60,000 operations per second, and could be used for any device -- including computers and robots -- that required a "brain" for accepting 【30】______ and following a program of 【31】______ to produce an output. Within five years, many very powerful microprocessors had 【32】______ .The invention of microprocessors 【33】______ the stage for the arrival of the microcomputer, or personal computer (PC)-- an affordable machine for 【34】______ The first PCs, in kit form, appeared in the mid 1970s, and by the mid-1980s machines such as the Apple Macintosh and those based 【35】______ a PC first 【36】______ by IBM in 1981 were popular throughout the world. The success of these machines led to an explosion of software, in 【37】______ a range of spreadsheet, word-processing, graphic, educational, and games programs. Since the 1980s, a number of strong-intertwined themes have 【38】______ the computer revolution forward, including a continuing increase in the processing power and decrease in the size and cost of PCs; a switch of emphasis from 【39】______ to linked machines, as evidenced by the growth of local area networks and the Internet; and the spread of computer applications into virtually every 【40】______ of home and business life.
【21】
A.integral
B.comprehensive
C.integrated
D.general