crc冗余校验的C++实现，并验证他的正确性，改动CRC码最后一位，验证他的正确性。-crc redundancy check C++ implementation, and verify the correctness of him, the last one changes the CRC to verify the correctness of his.

CRC即循环冗余校验码（Cyclic Redundancy Check）：是数据通信领域中最常用的一种差错校验码，其特征是信息字段和校验字段的长度可以任意选定。-The cyclic redundancy check code CRC (Cyclic Redundancy Check): A data communications of the most commonly used error check code, characterized in that the information f