I Know a directory is a file ,a special file,under linux.Every file
has a inode,a inode point to a block at least.

OK,first look at a example of ext2 directory:

offset inode rec_len name_len file_type name

0 21 12 1 2 . \0\0\0
12 22 12 2 2 .. \0\0
24 53 16 5 2 home
\0\0\0
40 67 28 3 2 usr \0

I know rec_len could be a offset to next entry. home and usr are
directory , has inode 53,67 for each,they are one by one (offset24
,offset40).

Now,my question is: If a inode point to a block,why difference of two
different inodes just is 16 (40-24) ???