READINGS

The computer is the most important invention since the type of engine was used in cars. Today it is the greatest effect on science，industry and business，but it？蒺s being used more and more in education and medicine. It has touched the lives of everyone. It？蒺s a revolutionary invention.

The oldest kind of computer is the abacus（算盤），used in China since the sixth century. In the seventeenth century an adding machine was invented，but the first large modern computer was built in 1937. Now the computations are so fast that they are measured in nanoseconds（毫微秒）.

Most computers are now stored-program（貯存式） computers，that is，they have a memory. They are getting smaller and smaller，and computing faster and faster.

Computers can report，decide and control in almost every field. Many computer scientists are now thinking of making the computer “think” like a man. A computer can draw pictures，write music，talk with people，translate languages and so on. Computers will one day really think and feel. Do you think that people will be afraid when they find that computers are clever enough not to listen to serve the people？

We hope that computers will take more and more of the work from man. People will almost certainly have to do less work. Each person will get only two or three days a week of work. This means that the rest of the time will be mostly leisure（休閑的） time.

The sea looks very beautiful when the sun is shining on it. It can be very terrible when there is a strong wind.

The sea is very big. It covers three quarters of the earth. The sea is also very deep in some places. There is one place and at that place the sea is about 11 kilometres deep. The highest mountain in the world is about 9 kilometres high. If that moutain was put into the sea at that place，there would be still 2 kilometres of water above it！

In most parts of the sea，there are plenty of fishes and plants. Some live near the top of the sea，and others live deep down. There are also a lot of small living things，lots of fish live by eating them.

The sea can be cold. When people go down，the sea becomes colder and colder. Only some men can go down into the deep sea. But about forty years ago，five women scientists live in the deep sea for fourteen days.

Maybe your maths teacher has already taught you how to find the centre of a circle. It isn？蒺t easy to learn and it takes some time to do so. Here？蒺s a simple method. This method can be learned in a few minute.

Put a corner of a square（正方形的） piece of paper on the circumference（圓周） of a given circle，and you？蒺ll see the two sides of the piece of paper meet the circle. And then you？蒺ll get two points on the circumference. You may name the Point A and Point B. You may be sure that Points A and B are the two ends of the diameter（直徑）. Draw a straight line through the Points A and B. Then do the same thing a second time in a different place to get another diameter. You？蒺ll find the centre at once： the two lines cross at a point and this point is just the centre of the circle.

How about trying to see if it is easy to learn and remember this simple method of finding the centre of a circle？