【正确答案】
D
【答案解析】[听力原文]
Thirteen hundred men and women are dressing up like astronauts. They put on white suits and pull on caps, boots and gloves. After walking through "air showers", where blasts of air remove dust particles from their clothing, the team is ready to work.
Are they preparing to perform operations on patients? Or are they shooting scenes for a science fiction film?
No. These people are the technicians who make the latest computer and video-game "brains"—Intel Pentium chips.
Intel technicians are high-tech electrical engineers. When they make Pentium chips, they"re building tiny interconnected electrical circuits—pathways through which electricity, a stream of electrons, can flow.
Because the circuits the Intel workers build are so small, even tiny dust particles can cause trouble. That"s why Intel technicians dress up like astronauts and make the chips in a superclean environment. Impurities like dust can cover and block the tiny electrical circuits.
In the computer world, blocked circuits are bad news. That"s because all the functions a computer performs depend on the flow of electricity. The specific function a computer performs at any one time depends on which circuits are on or off.
In order for your computer to understand which circuits should be on or off, every instruction you give must be translated into binary code. Binary is a number system that uses only two numbers—0 and 1.
Each binary digit, or bit, operates a tiny electronic switch on a computer circuit. "One" switches the current on, while "zero" switches the current off.
The main reason for the difference in speed is the size of the circuits. In the earliest computers, built in the 1940s, technicians constructed large circuits with bulky switches in glass tubes and miles of wires. A single computer could fill a room. These primitive circuits used a lot of electricity and overheated quickly.
Today"s circuits are far, far smaller. You can fit circuits with millions of switches on a single silicon chip. These smaller chips are faster because electricity doesn"t have to travel as far from one switch to the next. It takes less electric current to turn these tiny switches on and off. The computers use less power and they run faster.
So, what"s next in the high-tech world of computer chips? The dust-free circuit builders at Intel are working to bring an even faster chip to the market within a few years. This "Pentium Pro" chip will be twice as fast as the 32-bit Pentium chip. That means you can expect better programs, more video games, and more pictures.