计算校验和程序。其中Checksum是程序名；inputfile是输入文件，其中包含数据字段封装的内容；outputfile为输出文件，该文件保存封装后的整数据报。-Calculate Checksum procedures. Checksum is the name of the program　inputfile is the input file, which contains the contents of the data field encapsulation　outputfile for output file, the file is saved to the whole datagram encapsulated.