该系统要求实现一个简单的计算程序。主要功能计算两个大整数（ 20位）的加法和减法，且要按指定的格式输出结果。通过此课题，熟练掌握字符传、数组、格式输出、文件的各种操作，以及基本的计算算法思想的应用。-The system requirements to implement a simple computer program. Calculation of the main functions of two big integers (　20 bit) addition and subtraction, and according to the specified output format. Through this project, master character biography, array formats, documents a variety of operations, and basic computational algorithms applied thinking.