为帮助同学们完成PL0的课程设计，接下来我将对PL0的运行时数据栈（虚拟堆栈机）在程序运行时的变化情况、为编译器添加类型和函数的返回值及其参数传递作一些介绍。 -PL0 to help students complete the course design, then I would PL0 runtime data stack (virtual stack machine) in the changes in the program is running, add the type and