本程序是用纯C语言编的一个基于命令行的四则运算计算器。主要用于计算四则运算表达式的值，同时可以实现四种进制任意两种之间的转换。 主要功能：1.四则运算：能够解释并执行四则运算表达式。四则运算就是包含+、—、*、/、.（小数点）和数字的运算表达式，例如：3+2.9*（5-6/3） -4+（+8*6）等；　　2.错误警告：能够对不符合语法的表达式给出相应的错误警告,本程序共给出了8大类警告 3.进制转换：能够做二进制、八进制、十进制、十六进制中任意两种进制之间的互相转换 4.帮助系统：提供完善的帮助系统 5.出错保护：有良好的出错保护系统，命令行输入错误，程序仍能正常运行。-this program is pure C-language series based on a command line of four Operational calculator. Mainly used in the calculation of four computing the value of the expression, and can achieve four band arbitrary conversion between the two. The main functions : 1. Four computing : the ability to interpret and apply the four Operational expression. Four operations is included ,-,*,/,.( decimal point) and digital arithmetic expressions, for example : 2.9* 3 (5-6/3)-4 (8* 6); 2. Wrong warning : to be able to not grammar of expressions is the corresponding error warnings, the procedure is a total of eight major categories of warning 3. Decimal Conversions : can do binary, octal, decimal, hexadecimal arbitrary band between the two interchangeable 4. help system : to provide a comprehensive help