It’s complicated to explain!
Sigh!
On a disk, besides the files we can see,
there is also the disk’s own file storage format,
otherwise how would we know where the files are stored on a round disk!
For example, FAT32 and NTFS are both basic disk formats.
A disk is divided into N sectors, and each sector
is further divided into
clusters one by one.
Files are split up and stored in each cluster.
And each cluster is used like this below:
ID address file ID address
We usually can’t see those identification files.
That’s also why a formatted disk is a bit smaller than an unformatted one.
A 1.44MB floppy disk, after being formatted, only has about 1.38MB left.
The missing space is taken up by these hidden identification files.
To put it more accurately, an image file means those identification files are copied too.
So naturally the file will be a bit larger.
But not entirely,
because image files can be compressed,
so some files on the disk that originally could not be compressed also get compressed, so naturally the space
becomes a bit smaller.
Another very important reason for having image files
is that some files are invisible, but you still can’t do without them.
For example, the boot sector on a boot disk cannot be seen.
If we don’t use an image,
and just simply copy the files on the disk over,
the copied boot disk will not be able to boot the computer,
because it is missing that boot sector!
