The superblock contains information about this particular file system,
including, for example, how many inodes and data blocks are in the file
system (80 and 56, respectively in this instance), where the inode table begins
(block 3), and so forth. It will likely also include a magic number of some kind
to identify the file system type (in this case, vsfs).

You may notice that it is a bit of overkill to use an entire 4-KB block for
these bitmaps; such a bitmap can track whether 32K objects are allocated,
and yet we only have 80 inodes and 56 data blocks. However, we just use
an entire 4-KB block for each of these bitmaps for simplicity.

---

minor change in vsfs.py is needed to show the data which was written,
otherwise can't answer the question about data:
$ diff vsfs.py.ORIG vsfs.py
383c383
<             print 'fd=open("%s", O_WRONLY|O_APPEND); write(fd, buf, BLOCKSIZE); close(fd);' % tfile
---
>             print 'fd=open("%s", O_WRONLY|O_APPEND); write(fd, "%c", BLOCKSIZE); close(fd);' % (tfile,data)
$