练习材料：[Day 2781 2022-05-07]

L51-1:Predicting the future

Predicting the future is notoriously difficult. Who could have imagined, in the mid 1970s, for example, that by the end of the 20th century, computers would be as commonin people's homes as TV sets? In the 1970s,computers were commonenough, but only in big business, governmentdepartments, and large organizations. These were the so- called mainframemachines. Mainframe computers were very large indeed, often occupying wholeair-conditioned rooms, employing full-time technicians and run onspecially-written software. Though these large machines still exist, many oftheir functions have been taken over by small powerful personal computers,commonly known as PCs.In1975, a primitive machine called the Altair, was launched in the USA.

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练习感悟：27’。