双缓存存储类，通过两个缓存区的交替存储，减少磁盘的读写次数，节省cpu资源，要求读写时对cpu资源影响小的程序很有用
Cache storage class, alternately by the two buffer storage to reduce the number of disk read and write, save cpu resources, require readers to cpu resources affect small program useful (2012-07-11, Visual C++, 2KB, 下载21次)