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    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 pasting¹,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 think² how it works until it gets dirty and we have to learn how to clean it. We learn to point at things 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 screens。but the mouse is still our workhorse.

    The computer mouse was invented in l964 by Douglas Englehart of Stanford University. As computer screens became more 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 he very useful. The introduction of the mouse, with the Apple Lisa computer in l983, really started the computer public on the road to relying on the mouse for routine computer tasks.³

    How does the mouse work? We have to start at the bottom, so think upside down tor now. It all starts with the mouse ball. As the mouse hall in the bottom of the mouse rolls over the mouse Dad, 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 side⁴. 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.

5. So far we have only discussed the basic computer mouse that most of you probably have or have used：到目前为止.我们只限于讨论基本型的电脑鼠标,你们中间多数人也许拥有一个鼠标,也许你们已用过鼠标。

电脑鼠标

    电脑鼠标是一个惊人的巧妙发明，它设计简单，但却使我们能够对电脑屏幕上的东西进行非常有效的指挥。想想你可以用鼠标做的那些事情，比如复制粘贴，绘画，甚至用新式鼠标上的滚轮使网页上下滚动。我们大多数人每天都用电脑鼠标，却从来没有停下来想想它是怎样工作的，直到有一天它变脏了，而我们又必须学会如何对它进行清洁。我们会说话之前就已经学会用手指东西，所以鼠标是一个很自然的指针设备。其他电脑指针设备还包括光笔，图形片和触摸屏等，但鼠标仍然是我们的主要工具。

    电脑鼠标由斯坦福大学的道格拉斯·恩格尔哈特在1964年发明。随着电脑屏幕越来越受欢迎，而且箭头键可以在一个文本上随意移动，人们认识到一个能自由移动甚至选择文本的游标装置将是非常有用的。l983年鼠标的引进和苹果电脑丽莎的开始使用，使广大电脑用户开始踏上一条依赖鼠标完成常规电脑工作的道路。

    鼠标是怎样工作的?我们得从底部开始，所以现在把鼠标倒过来看。一切都开始于鼠标球。当鼠标底部的球在鼠标垫上滚动的时候，它压迫到两个滚轴并使其转动。这两个轴上有一些小孔，并与滚轮相连。滚轮两边各有一个叫做发光二极管的小型电子发光器件。其中一个发光二极管向另一个发出一个光束。当滚轮转过一个小孔时，光束通过小孔到达另一边的发光二极管。但稍后该光束被阻塞，直到下一下孔转动到这个位置。发光二极管检测出光束的变化模式，将该模式转换成电子信号，并通过一条延伸出鼠标的电缆将信号传输给电脑，这条像尾巴一样的电缆正是鼠标得名的原因。电脑通过解读信号确定光标在电脑屏幕上的位置。

    到目前为止，我们只限于讨论基本型的电脑鼠标，你们中问多数人也许拥有一个鼠标，也许你们已用过鼠标。这样的设计带来的一个问题是，滚球滚动时表面吸附的灰尘会使鼠标变脏，所以最终你必须对它进行清洁。较新的光学鼠标由于没有可移动的部件就避免了这一问题的产生。