i once saw a .rar file which was less than a megabyte, and when i extracted it, it was around 1.8GB.
does ayone know how to compress a file this well?
thanks
Full Version: Compressing Files With Winrar
Generally with almost all data that is impossible.
What was in the .rar? Empty, or mostly empty, files compress very well and could do that.
Example. When I back up my 40GB hard drive with 15GB used I get a 40GB file. There is an extra 25GB of empty information in my backup file. When I compress the backup file it shrinks down to 15GB.
What was in the .rar? Empty, or mostly empty, files compress very well and could do that.
Example. When I back up my 40GB hard drive with 15GB used I get a 40GB file. There is an extra 25GB of empty information in my backup file. When I compress the backup file it shrinks down to 15GB.
File compression in it's simplest form,finds redundant data, catalogues it in a dictionary giving it a unique identifier, and whenever an instance of the phrase (using text as an example) is found, puts the identifyer in it's place, saving space.
Redundant data is data that is unecessarily inputted more than once. Text files can be readily compressed as words have alot of patterns to them, otherwise they would just be jumbles of letters.For example:
This could be compressed by:
And anything that has been programmed to read the compressed file can uncompress it back to its original form.
Here is another way the data could have been compressed:
So the megabyte file you downloaded can easily be over 1.8Gbs uncompressed. All they need to do is copy something thousands of times and rar it
Redundant data is data that is unecessarily inputted more than once. Text files can be readily compressed as words have alot of patterns to them, otherwise they would just be jumbles of letters.For example:
CODE
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
The cat ate my hat.
This could be compressed by:
CODE
Dictionary
The cat ate my hat.=1
Data
1
1
1
1
1
The cat ate my hat.=1
Data
1
1
1
1
1
And anything that has been programmed to read the compressed file can uncompress it back to its original form.
Here is another way the data could have been compressed:
CODE
Dictionary
The=1
cat=2
ate=3
my=4
hat.=5
Data
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
The=1
cat=2
ate=3
my=4
hat.=5
Data
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
So the megabyte file you downloaded can easily be over 1.8Gbs uncompressed. All they need to do is copy something thousands of times and rar it
the file was a .mdf which i mounted and used to play a game although it was only instead of a crack and not the full dvd which would install as well
Sounds like they made an image of the game, then just replaced all the installers (and whatever the game protection doesn't call on to make sure you have the disc) with null data, which as enc says compresses easily.
ok thanks for the info
cheers
cheers
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