压缩包里包含算术码压缩和解压到源代码，能够对大小写字母进行压缩，包含测试文件，对测试文件的内容压缩率可达到50 。主函数部分有详细的解释。-In this compressed packet,it include the source code of arithmetic coding and decoding.And it can compress all character with a test file.The compressive ratio can achive 50　for the test file.It has detailed explanation in the main function.