VC++简单的表达式求值程序，一直很想做个比 Windows 自带的高级一点的计算器，能将整个表达式输入，然后求值，现在终于做出来了，还有些不完善，源代码用到了编译原理的一些知识，新入门的VC++朋友估计会感觉有点难。

-VC++ simple expression evaluation process, always wanted to be a little advanced than Windows built-in calculator, can enter the whole expression, and evaluation, it finally did come out, have some imperfections, the source code is to some knowledge of compiler theory, the new entry in the VC++ Friends is expected to feel a little difficult.