参考答案：Students talk about the pictures on the textbook with the teacher’s help.
An abacus is an old calculating machine used in China until now.
A huge computer is built to solve some mathematical problems. But it is too big.
A calculator is a new calculating machine which can solve a large number of mathematical problems.
A PC is a personal computer which can solve all kinds of problems and is used widely now.
A notebook computer is a kind of useful computer which can be taken conveniently like a notebook.