生成一个文本文件，文件包含一定记录。给记录加个属性属性，假定A为整数类型。Block的大小可在自己的操作系统上查看，。在内存分配50M字节的空间用于外部merge-sort-Generates a text file with a certain record. Add to the record Properties, assume that A is an integer type. Block size is available on its own operating system view. 50M bytes of memory space allocated for external merge-sort