主要让使用者了解何谓变数，及变数的替换；所谓的变数，即是用来存放各种资料的容器，这些变数都有

各自的名称，名称皆不能重复。-Allows users to know what is meant by the main variables, and variable substitution　the so-called variable, that is used to store various types of information containers, these variables have their own name, the name should not duplicate all.