With the malce molds and an unlimited number of machines can be build with locally protracts purchased metal points parts .

使用这些模型，再加上在当地购买金属零件就可以无数台机器。

In practice, we often need observe characteristic curves of all apparatus. These curves are hardly drawed by hand directly, but using MATLAB protracts the curves rapidly and briefly.

在实际中，我们常常需要观察各种器件特性曲线，这些曲线很难用手直接画出，利用MATLAB则可以较快捷，简单的绘制这些曲线。