File archives is a certain file created with the help of a special program called an archiver, and containing from one to several files and / or directories (folders) in a packed form.
Historical aspect
Such archives were most actively used during the use of floppy disks, since file archives allow you to compress some types of files (excluding graphic and video) in order to place them on a small volume of floppy disks. With their disappearance, the use of archives basically moved to the Internet, where they continue to be used primarily in file hosting and ftp-servers.
Archive Classification
The following types of file archives are distinguished:
- regular - in one archive file there are several files and / or folders compressed by any method;
- self-extracting - are executable files with the extension .exe; at startup, you only need to specify the unpacking path, the rest will be done by the program itself;
- multivolume - includes a number of archive parts, which, in addition to their own extension, can have an additional one showing the part number: part01 ...;
- continuous - archives with the highest possible compression ratio, in which all files and folders are a single whole; unpacking of one file (folder) is not possible;
- Password protected - archives that require a password to open.
File Archive Extensions
Each file has certain extensions. File archives are no exception. This is, first of all, zip, rar, 7z - the most popular extensions used in the Windows operating system. Such extensions in the GNU / Linux OS can be found very rarely, mainly from those users who recently switched to using this OS after Windows. Here the most common archives are gz, bz2, xz. Work with these extensions is usually accompanied by tar compression, as a result of which the general extension looks like tar.gz, tar.bz2, tar.xz. Often tar.bz2 and tar.xz are more efficient in compression than zip. These formats are not common in Windows, but can be successfully used there in all common archivers.
The best compression ratio in the most common Windows OS is 7z, however, the tests performed show its slight superiority over other file archive extensions. Working with zip on Windows is available after the installation of the system, just like on Mac OS X, most GNU / Linux distributions also work with this archive out of the box, since archivers are installed with the distribution, which support most common file archive formats.
Work with file archives
File archives assume the existence of special programs that could effectively create and unpack them. It should be noted that most archivers for Windows create the corresponding items in the context menu, which is called by right-clicking. We will look at file archives for desktop computers, but there are those for gadgets that can be found in the respective stores.
Consider the most common file archive programs.
Winzip
By default, it saves files in zip, but you can save in other formats. Using this archiver you can compress mp3 files, as well as jpeg files up to 25%, without losing quality. The compression method is automatically selected. There are functions for printing files that are compressed into this archive, checking them with antivirus and others. Recent versions of the application support opening 7z, rar and zipx files.
According to the assurances of the developers, WinZip provides protection using bank-level encryption. In addition, the latest versions have the opportunity to connect to the clouds.
In this program, new file formats of MS Office documents can be opened as file archives: docx, xlsx, etc., as well as formats that comply with the international ODF standard.
According to the developers, the reduction in the size of graphic files is due to the fact that some formats are replaced by others.
In case of accidental deletion, copying, renaming files can be restored.
Winrar
In the world, zip archives are leading in popularity, but Russia goes its own way, and we have the most popular archiver - WinRAR. This archiver has a command line mode (it is used in GNU / Linux environments), the latest versions have also learned how to efficiently compress media content. It has its own compression algorithm, supports a variety of formats, including both the popular rar and zip, as well as the less popular gz, tar, bz2, lzma and others.
In WinRAR, you can choose the compression time, but keep in mind that stronger compression will lead to a large investment of time in the archiving process. In the settings of this archiver, you can set a low priority, which will increase the load-unpack time, but also reduce the load on the processor, and you can use all the processor cores, which will lead to their stronger loading, but will reduce the time of creating the archive or unpacking.
Peazip
This program is cross-platform and can be installed on many operating systems. It is capable of opening more than 180 file archive formats. This is probably a record. It supports simultaneous work with multiple archives. The latest versions provide support for opening zipx, rar, including its fifth version.
This application also supports data encryption, it has the ability to convert a disk to the NTFS file system, it is possible to create keys, backup files. The program is released both for 32-bit platforms and for 64-bit ones.
7-zip
Using this archiver, native 7z formats are created, although a number of others are supported, including popular formats on Windows and POSIX systems, including GNU / Linux and Mac OS X. It, among others, allows you to open rar, deb archives that contain binary GNU / Linux program installer files. According to the developers, the compression ratio exceeds WinRAR by 30-70%, and WinZip - by 2-10%.
Unlike the first two archivers who want to get money from users for their use, the last two relate to open source programs and are free. In 2007, this archiver was recognized as the best project by SourceForge.net.
Encryption is implemented using the AES-256 algorithm for 7z and zip file archives. Archives packed using the LZMA method are unpacked literally on the fly.
Like PeaZip, there are applications for both 32-bit and 64-bit platforms.
Internet file archives
Many servers on the World Wide Web contain them. Internet servers containing file archives are called ftp servers. Until recently, on these servers you could find almost everything - from music to toys and programs for various systems. The fight against piracy in our country has somewhat crippled this segment, and now free products are mainly located there.
GNU / Linux OS repositories are located on ftp-servers, so that each user of these systems can freely install programs signed with digital keys, which eliminates the possibility of malicious code penetrating the user's computer, which makes these systems famous for the absence of viruses.
FTP servers can be viewed from any browser, and there are special clients for them.
Data exchange between the ftp server and users occurs via the TCP channel. Exchange management is regulated in the TELNET protocol standard.
When using the ftp protocol, it is possible not only to download files to a local computer, but also transfer them to a remote server.
Any interested person can use the file archive system using the ftp server.
These servers provide the provision and receipt of file archives by both anonymous users and authorized users. Most ftp servers are anonymous.
Despite the advantages described, ftp-servers are not without drawbacks. A huge part of the file archives in them is presented without a description, and you can only guess what is in front of you by a targeted search.
Files can be transferred in text or binary. If you select the wrong file, the file may be damaged.
There is no universal search for ftp servers. There are several solutions, but all of them are not universal.
The most common among them is the Archie service. Archie servers are heavily loaded and work only with anonymous ftp. However, the server data is decentralized, the search is carried out according to an incomprehensible algorithm, as a result of which, after going through all the servers (and there are about a dozen of them), you can not find the required information. In addition, you must be able to create a search template when using this service.
In addition to using the ftp protocol, http can be used to access file archives.
In file archives, they represent not only open source software; there you can find various texts, demo versions of proprietary programs, and much more.
Finally
Thus, file archives are a necessary thing in order to transfer a large amount of information in a compressed form. This archives can be used both locally - on individual computers, and on the global Internet through the use of special ftp and http servers. The most common programs for creating archives and unpacking them are WinRAR, WinZip, PeaZip, 7-zip. The last two programs are free and can be used for free. Most archivers support all the most common archive formats.