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  3. Computer Mouse The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to p

Computer Mouse The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to p

admin2013-09-17  64
问题                            Computer Mouse
    The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to point at things on the computer and it is very productive. Think of all the things you can do with a mouse like selecting text for copying and pasting, drawing, and even scrolling on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it works until it gets dirty and we have to learn how to clean it. We learn to point at thing before we learn to speak, so the mouse is a very natural pointing device. Other computer pointing devices include light pens, graphics tablets and touch screen, but the mouse still our workhorse.
    The computer mouse was invented in 1964 by Douglas Englehart of Stanford University. As computer screens became popular and arrow keys were used to move around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse for routine computer tasks.
    How does the mouse work? We have to start at the bottom, so think upside down for now. It all starts with mouse ball. As the mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts. The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices called light emitting diodes(LED)mounted on either side. One LED sends a light beam to the LED on the other side. As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other side. But a moment later the light beam is blocked until the next hole is in place. The LED detects a changing pattern of light, converts the pattern into an electronic signal, and sends the signal to the computer through wires in a cable that goes out the mouse body. This cable is the tail that helps give the mouse its name. The computer interprets the signal to tell it where to position the cursor on the computer screen.
    So far we have only discussed the basic computer mouse that most of you probably have or have used. One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up the dirt. Eventually you have to clean your mouse. The newer optical mice avoid this problem by having no moving parts.
The key components of a computer mouse are the two LEDs.
选项 A、真
B、假
C、Not Given
答案A
解析 利用题干句中的特征词two LEDs搜索原文，发现他们出现在原文第三段后半部分，内容是关于两个发光二极管在鼠标中的具体工作方式。第三段说道：鼠标的部件有滚动部件如滚球，还有光电装置如二极管等。二极管将光信号转换为电信号，传送到计算机，计算机根据收到的电信号作出相应的反应，因此，二极管是鼠标的主要部件，而滚轮等只是辅助性的机械部件。题干句对短文信息的推断是正确的，故答案为A。
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