Thursday, February 22, 2007

What is a Rar Archive Anyway?


OK, I have been meaning to cover this for so long now and, judging by the amount of e-mails I receive on the subject, it is still a major issue for lots of you.
I will attempt to clear up some of the most commonly found problems regarding opening Rar Archives. Firstly though:

What is a Rar Archive Anyway?

First off, Rar archives are simply files that are used to 'pack' other files. Let's imagine that you have a set of ten files. The rar archive is like a box; you can put them into it, close it up and then, like when sending through the mail, you send it over the Internet and it is opened at the other side, the box is then discarded.
The main function of 'archiving' is to reduce the size of the files. The archiving process applies compression to the data or files that you place inside. Some file types can compress very well and some not very well at all. Some files are already of a compressed format, like MP3 files for example; they don't usually reduce much when archived...look at the picture below, the setting for compression (reducing the size) was at the strongest setting but the files as you can see, didn't reduce by much.

Compare the above, with this image of a bitmap image file in a rar archive on the same high compression seting.

The reduction in size of the file is AMAZING. So for people who use the internet to transfer files to and from locations, using Winrar is a must! If you only reduce the size by a small amount, it is still worth it. Why send extra data all over the place when you just don't have to?

So Rar Archives are not some great complicated mystery. They are, in fact, very simple to use and are really useful for a number of reasons. You can put files into a Rar Archive and then protect the Archive a password. This is great as a way of stopping these free file hosting services from knowing what is inside the files! And anyone else for that matter.
You can also put large sized files into a Rar Archive and then it can split the file for you, to be rejoined later. This is invaluable for say... I want to send you a movie file. It is 700Mb! I cannot find a free host service to use and also the uploading of it might disconnect as it would take a bit too long. so I put it into a Rar Archive and set it to split the output to files of 100Mb. The result is a set of seven Rar Files each of 100Mb in size. Then I can easily upload these, you can download them and open them easily. You then take the large file out of its 'box' and you have your movie file to watch.
More about file splitting later.
I want to concentrate on common problems with rar archives that you might come across so that is my next post.

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Blogger Alex said...

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November 03, 2010 1:24 PM  

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