How do .zip files work?

[dlinkwit27]

Well, how do they? and Why don't OS and files jsut make themseves smaller by default?

[zootm]

there are many, many ways of compressing data. i'm not really an expert so i can't answer your first question.

the answer to the second one is that it takes CPU time and resources to compress and decompress files - zip files are fine for things you don't use much, but to use a file you have to unzip it - if this is a system file, you don't want to be constantly zipping and unzipping every time you change or use the file. it would slow your system down an awful lot.

[dylman]

http://computer.howstuffworks.com/file-compression.htm

[godoncrack]

winME and XP both have built in compression

[mikm]

It isn't as powerful as a standalone, though.

[Merlin]

The built-in NTFS compression in windows XP annoys me. All it does is slow down certain apps. I have 40+ gigs of free space, I don't need to compress a 400K text file.

Haven't found a way to turn it off. Disk Defragmenter insists on compressing files when it really doesn't need to.

[Viper007Bond]

What annoys me is that programs like Winzip don't compress accross multiple files. If you zip 8 identical images, it should only be slightly larger than the size of one of those images zipped. :-/

Merlin - like are all files showing up as blue? (XP's code for compressed) If so, just right click the foler, hit properties, then advanced, then uncheck "compress contents to save diskspace" or whatever it's called.

[Merlin]

Yeah, but that doesn't stop it getting compressed in the first place, which would be better.

Love the font you're using for audio-tracker.

[bored154]

zip just has them in temp then decompresses them and moves them to the folder you want(thats what i think im probabily wrong i know). My reason for believing that is because it says moving from what ever temp folder it has it in to the folder you are sending it to.

[eleet-2k2]

Originally posted by dlinkwit27
Well, how do they? and Why don't OS and files jsut make themseves smaller by default?

In answer to your last question, it sounds like you mean: "Why doesnt Windows just say it's a smaller file size?". If that's the case, then it's wrong to ask that question because a program cant just dictate an arbitrary size for a file, like a 100 MB movie file occupying 100 KB of diskspace, because file contents are dictated by teh amount of bytes written to them, and in essence how many bits of data on the hard drive were used to store the entire contents of the file, which, in total is the size of the file. It would be nice to have the movie example be true, but out data would corrupt quite easily as we cant just expand out physical capacity just cuz you want it to.

If you meant compression wise, "Why cant the compression be better and stronger to make smaller files?", then it all depends on the crazy math and algorithms used, but I'll bet that eventually, mathematically, it's impossible to compress beyond a certain point.

[dlinkwit27]

I meant the second one. If a program can be compressed, why does the OS jsut not do that in the first place, but zootm 'splained why that wouldn't work.

[teh Nightwing]

MAN.....I REMEMBER WHEN ALL WE HAD WAS DOS! And you could get MSUNZIIP.ExE and add it to your c:\dos\command\ file! And....it was so great!

[teh Nightwing]

^OOPS! I meant PKUNZIP.exe

[dlinkwit27]

use that button next time plase.

[DragonSon]

Mayhaps Atmo could enlighten us all...

[teh Nightwing]

HAH! Crap.....Sorry! I didn't even use the edit button! Please forgive me everyone! I usually do but....I don't know what came over me

[liquidmotion]

HUFFMAN ENCODING!

[s0be]

in response to zipping multiple identical files...

under unix, you generally make tar.gz/bz2 files.

what tar does is take all the files and merge them into a single file. Then your choice of compression programs (bzip2 is better than gzip, which is compatible with regular old zip) compresses the tar file. it's slightly slower to compress this way because it has to search a much much larger file for patterns, but it can save quite a bit.

s0be

[Viper007Bond]

Originally posted by Merlin
Love the font you're using for audio-tracker.

Me too! Credits to gigantus for giving it to me to install on my AT remote. Here's the font if you're interested.

http://www.1001fonts.com/font_details.html?font_id=2578

[Coman]

howstuffworks is great, it explains everything.

[bored154]

even how to pic a lock

[Coman]

where? linky?

[bored154]

http://home.howstuffworks.com/lock-picking.htm

they have little flash things or something to show you step by step

[Coman]

man that's great.

one of the authors of the site used to be my neighbor

[bored154]

cool, did you help him or give him some ideas?

[whiteflip]

When you put a bunch of identical files in a zip file try zipping the zip file. The new zip file will see the patern in the old zip file and compress it all

Or you can put all the pictures in a cab file.

[Coman]

of course.

[Starbucks]

If you zip 8 identical images, it should only be slightly larger than the size of one of those images zipped. :-/

Image files already contain their own compression, so further compression won't make it much smaller. Same goes with ISO files. I've got one that is 700MB, extracted is 1.6GB!!

[whiteflip]

Starbucks I beleive you misread his statement.

Even with a compressed image format like shitty jpegs or awesome PNG's if you have 8 identical files for some odd reason and you compress those 8 identical files into the same zip file than the zip file should recognize the pattern across the multiple files and just zip it once and add the extra data in the zip file to say that when you view or extrat any of the 8 image files that its comming from that single source dilly.

Makes senese?