说明：  题目实现DOS中的COPY命令。可首先打开源文件和目的文件，其次顺序读取源文件每个字节赋给目的文件对应位置，源文件读完时，目的文件也自然拷贝成功。
(Title achieve the DOS in the COPY command. Be the first to open the source file and destination file, followed by sequential reads the source file is assigned to the purpose of the file corresponds to each byte location, the source file read, the purpose of copying documents the success of the natural.)