C语言实现 一个自然数的七进制表达式是一个三位数，而这个自然数的九进制表示也是一个三位数，且这两个三位数的数码顺序正好相反，求这个三位数。-C language a natural number is a seven-digit hexadecimal expression, and this natural number is a nine-digit hexadecimal representation, and the two-digit digital opposite order,

C预言师实现： 请编写一个程序计算表达式：data1 op data2的值。其中，op为运算符＋、－、*、/。-C prophecy teacher realized: Please write a program to calculate the expression: data1 op data2 value. Which, op as operators+,-,*, /.

a. C语言概述，C程序文件结构 b. 数据类型，运算符，表达式 c. 程序结构if, switCh, while等-a. C Language Overview, C program file structure b. data types, operators, expressions, c. program structure if, switCh, while, etc.