directory table的用法和样例：
例句
- A book usually has a table of contents.
一本书通常都有一张目录表。 - When the operating system moves a file from one directory to another on the same drive, it merely relocates the file's entry in the disk's table of contents.
当文件从一个目录被移动到同一个硬盘下的另一个目录下时，操作系统仅仅是修改一下该硬盘的目录表，并不做实际的文件删除和重写文件操作。
