[24hoursupport] Re: zip and unzip files

  • From: "Ron Allen" <chizotz@xxxxxxxxxxx>
  • To: 24hoursupport@xxxxxxxxxxxxx
  • Date: Sun, 16 Jun 2002 23:00:09 -0500


> Can I ask what is the favorite free program to zip and unzip files?
> I tried to compress and zip a file and I took a 2,200KB file and
>compressed it to 2.2MB and zipped it.   now I think thats just a little
>backwards lol
>  I have windows XP and the file is in "my documents" and when
>highlighting it and left clicking it says " send to" then I click on
>"compressed zipped folder"  and it gets bigger....Thanks for any

My favorite is WinZip ( http://www.winzip.com ), but it does cost about $30
or $40. 

Another, cheaper, alternative, is PowerZip (
http://www.trident-software.com/ ) at about $20.

Finally, there is UltimateZip ( http://www.ultimatezip.com/ ) which is FREE

Comment: the main reason my favorite is WinZip is because I paid for it
long ago, and I mean like 10 years ago or so, and am still getting free
upgrades so there has never been any reason for me to change :) It's also
very easy and fairly intuitive to use, but it doesn't use the latest
Windows Explorer style "tree" metaphor (not necessarily a bad thing in my
opinion, but that's probably another topic). It does integrate into the
Windows shell, meaning that it adds items to the right-click context menus
so you can right-click a file in Explorer and choose several options for
zipping it. Windows will automatically see the zip file as a zipped folder,
too, and will also see zipped files created by other programs as a zipped
folder too.


The compression you can expect on any given file varies wildly depending on
what kind of data is in the file. I've seen some files compress as much as
90% and others that compressed 1% or less. In the case of compressing a
file that is already compressed, you can, indeed, even end up with the
compressed file being larger than the original.

The reason that this happens is because compression programs basically work
by looking for patterns in the data. For example, many letters and text
files probably contain the word "the" in many places. If we assume one byte
for each character, that's three bytes. If that word appears 100 times, it
takes up 300 bytes total. A compression program reduces that size by
storing the sequence "the" once, along with a list of locations in the file
where that sequence occurs. That could conceivably reduce the storage need
for this (highly simplified and idealized) example down to 103 bytes, 3
bytes for the sequence and one byte for each of the locations. 

A file that is already compressed has very few, if any, sequences that
repeat and are therefore further able to be compressed. In fact, since the
compression program adds a small amount of "overhead" regardless, such as
headers that indicate what kind of compression is used and so on, you can
end up with the doubly compressed file being slightly larger than the
original compressed file.

Good candidates for compression are things like word processing files, text
files, spreadsheet files, many bit mapped image files, etc.

Poor candidates for compression are files that are already compressed, such
as .jpg image files, many types of movie and music files, and files that
have already been zipped.

So the reason your 2.2 megabyte file didn't reduce when you made it into a
zipped folder is probably because the file itself is already stored in a
compressed format of some kind, not because of some flaw in the compressed
folder function.



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