文件存储空间管理可采取显式链接（如FAT）或者其他方法；
空闲空间管理可采用位图或者其他方法；
文件目录采用多级目录结构，目录项目中应包含：文件名、物理地址、长度等信息。(File storage management can take explicit linking (such as FAT) or other methods;
Free space management can employ bitmaps or other methods;
File directory uses multi-level directory structure, directory project should include: file name, physical address, length and other information.)