快速查题-汉语言文学本科试题

【*】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 get 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.

【*】For a century and a half the piano has been one of the most popular solo instruments for Western music. Unlike string and wind instrument, the piano is completely self-sufficient, us it is able to play the melody and its accompanying harmony at the same time. For this reason, it became the favorite household instrument of the nineteenth century.

【*】The ancestry of the piano can be traced to the early keyboard instruments of the fifteenth and sixteenth centuries--the spinet(小型立式钢琴), the dulcimer(洋琴), and the virginal(小键琴) In the seventeenth century the organ(管风琴), the clavichord(古钢琴), and the harpsichord(大键琴) became the chief instruments of the keyboard group, a supremacy they maintained until the supplanted them at the end of the eighteenth century. The clavichord's tone was metallic and powerful; nevertheless, because of the variety of tone possible to it, many composers found the clavichord a sympathetic instrument for intimate chamber music. The harpsichord with its bright, vigorous tone was the favorite instrument for supporting the bass of the small orchestra of the period and for concert use, but the character of the tone could not be varied save by mechanical or structural devices.

【*】The piano was perfected in the early eighteenth century by a harpsichord maker in Italy (though musicologists point out several previous instances of the instrument) This instrument was called a piano e forte ( soft and loud), to indicate its dynamic versatility; its strings were struck by a recoiling hammer with a felt-padded head. The wires were much heavier in the earlier instruments. A series of mechanical improvements continuing well into the nineteenth century, including the introduction of pedals to sustain tone or to soften it, the perfection of a metal frame, and steel wire of the finest quality, finally produced an instrument capable of myriad tonal effects from the most delicate harmonies to an almost orchestral fullness of sound, from a liquid, singing tone to a sharp, percussive brilliance.