1、　　以字符序列的形式从终端输入语法正确的、不含变量的证书表达式。利用一定的运算符优先关系，实现对算术四则混合运算表达式的求值，并且在求值中运算符栈、运算数栈、输入字符和主要操作的的变化过程。
2、　　设置运算符栈和运算数栈辅助分析算符的优先级。
3、　　在读入表达式的字符序列的同时，完成运算符和运算数的识别处理，以及相应的运算。
4、　　在识别处运算符的同时，要将其字符序列形式转换成整数形式。
5、　　在程序的适当的位置输入运算符栈、运算数栈、输入字符和主要操作内容。
,1, to form a sequence of characters input from the terminal grammar correct, non-variable expression of the certificate. The use of a certain operator precedence relations and the realization of the four mixed arithmetic expression for computing the value, and value in order to stack operator, computing the number of stacks, input characters and major changes in the course of the operation.
2, set up operator stack operands stack and operator-assisted analysis of the priority.
3, in the time sequence of characters into the expression at the same time, the completion of operator and operator identification numbers, as well as the corresponding arithmetic.
4, in the identification Office operator at the same time, to form the character sequence into the form of an integer.
5, in place procedures for the importation of the operator stack, the number of stack operations, input characters and the main operation of the content.