The archiving programs compress the information contained in the external memory of the computer. To achieve this, they use special algorithms developed for this purpose. For example, if a file has 50 characters appearing one after another, they can be replaced in the archive file that will contain the sequence 50A. Of course, the algorithms used are extremely complex. Each archiving program runs in fact, many algorithms.
An archive file is created using an archiving program. An archive can contain one or more compressed files and directories, in accordance with the hierarchical structure of its contents.
The main advantages of using archives are:
Spacing data saved thanks to the compression of files; the external memory has a storage space which is limited and in principle quite small, so this is quite an advantage.
Facilitates the transport of data on disk.
Protects against viruses, usually viruses do not infect the archives, but only the executable files or documents.
Faster to copy when working with many small files.
The possibility of a backup of the data is used very often, because the copies are small. However, they have a big disadvantage, namely, the files contained cannot be used directly, but only after their decompression. This decompression usually takes a long time and therefore, the data is only used very rarely, when it is decompressed.
The most commonly used operations with archiving programs are:
To create a new archive containing a specific directory structure;
To automatic delete files that are stored on your computer, immediately after their compression (this is used when the external memory space that is created for the archive is not enough to retain and archive the files in their uncompressed form);
To extract one or more files from the archive;
To protect the archive using a password, without which other people cannot extract files from it;
To have the possibility of creating an archive of several files whose size is specified (usually, this feature is used to copy a large amount of data on diskettes).
The most common standard today and in fact preferred for archiving and also one of the top programs available for download, is ZIP format. However, it does not have the best rates.
The archiver called WinRAR is a popular and widespread archiving program, whose performance did not disappoint in the past. The new version of this application, developed by Eugene Roshi, brings a radical improvement of the compression rate and of the time of data packing. This definitely reflect the position occupied in the rankings, WinZIP having a better position. As with WinAce, the interface has been a bit embellished, but the principles of previous versions have been broadly maintained, so that its ordinary users will not need time to adapt.
The range of functions is as extensive as in previous versions, including new items: how to integrate with Windows or the History tab and Favorites menu. The compression rates are those presented on the WinAce, WinRAR sites.
There are also DOS archivers, but they are hard to use and the instructions are difficult to learn, if you are not used to DOS. These DOS archivers were extensevely used in the Windows era, not anymore. Anyway, the compression rate used by them is significantly higher compared to the one used 10 years ago let’s say.
