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An archive is a single file that contains any number of individual files plus information to allow them to be restored to their original form by one or more extraction programs. Archives are convenient for storing files. For example. they make it easy to locate all files in a particular category or related to a particular project at a later date. They also allow the directory tree structure (i.e., hierarchy of directories) in which the files were originally contained to be maintained. Archives are also convenient for transmitting data and distributing programs. In fact, most software that is distributed over the Internet is distributed as an archive that contains all related files as well as documentation. Moreover, archives are very easy to work with, often much easier than dealing with large numbers of individual files. For example, it is a simple matter to compress an archive in order to reduce its size and transmission time and then decompress it after receipt. Also, it is possible to read, extract or insert individual files into an archive without first restoring all of the contents of the archive to their original form. Moreover, large archives can easily be split into segments for such purposes as sending as e-mail attachments or storing on floppy disks, even if they have been compressed, and they can later be reassembled without compromising the integrity of the data. The tar (i.e., tape archive) command, originally designed for tape backups, is used extensively for archiving and unarchiving files and directories on Unix-like operating systems. Several other common commands can also be used to create archives, including bzip2, zip, cpio and even the simple cp command. Some of these programs, such as bzip2 and zip, combine archiving with compression. tar does not, but is easy to compress archives created with tar using compression utilities. WinZip is the most popular archiving program for use on Microsoft Windows operating systems. It also has compression and encryption capabilities.
Created July 28, 2005. |