Question about Zip files

[MythicDawnAssassin]

Allright; I'm following coputer science at university and I'm really wondering how a Zip file works.

You see there is this file called MyMod.esp which is 47 kb large. I put it in a Zip file called MyMod.zip and that's only 8 kb large! THAT'S IMPOSSIBLE right? at first I thought it was a serious bug in my system, but I havn't got any complains when I uploaded it, so it's allright. I'm still wondering though: HOW can a computer make a file smaller and still preserve all the content in it? Anyone know?

[Quetzlsacatanango]

The basic premise - data on your hard disk is a bunch of numbers. In order to compress it, a program like WinZip, 7Z, or any other turns the file into a long number and looks for repeating patterns in that number. So, for example, if there was the string "1035489452130" and it occured in the long number 50 times, it would substitute "1035489452130" with a Z. So you can see right away how Z is shorter than "1035489452130". Then multiply it by 50 as in our example and you can see how you can gain dramatically smaller files in some cases. This is also why if you try to put, say, an mp3 into a zip file, you will get almost no file size change. An mp3 is already compressed.

Then, when you decompress (unzip), it puts "1035489452130" back in in place of Z, giving you back your original data.

Obviously modern compression software takes this idea to extremes and does all kinds of tricks with it, but that is the basic concept.

[LordTenaim]

MythicDawnAsassin you were not the only one wondering about that I think the response from Quetzlsacatanango is most intressting and explains nicely.

[Deleted54170User]

I read it somewhere else and it true what was written. Nicely done! You deserve a kudo for that.