In computing, an archive file is a computer file that is composed of one or more files along with metadata. Archive files are used to collect multiple data files together into a single file for easier portability and storage, or simply to compress files to use less storage space. Archive files often store directory structures, error detection and correction information, arbitrary comments, and sometimes use built-in encryption. Applications Portability Archive files are particularly useful in that they store file system data and metadata within the contents of a particular file, and thus can be stored on systems or sent over channels that do not support the file system in question, only file contents – examples include sending a directory structure over email, files with names unsupported on the target file system due to length or characters, and retaining files' date and time information. Additionally, it facilitates transferring high numbers of small files such as resources of saved web pages, since a container file is transferred using a single file operation, whereas transferring many small files requires the computer to modify the file system structure for each file individually, making it considerably slower. Software distribution Beyond archival purposes, archive files are frequently used for packaging software for distribution, as software contents are often naturally spread across several files; the archive is then known as a package. While the archival file format is the same, there are additional conventions about contents, such as requiring a manifest file, and the resulting format is known as a package format. Examples include deb for Debian, JAR for Java, APK for Android, and self-extracting Windows Installer executables. Features Features supported by various kinds of archives include: converting metadata into data stored inside a file (e.g., file name, permissions, etc.) checksums to detect errors data compression file concatenation to store multiple files in a single file file patches / updates (when recording changes since a previous archive) encryption error correction code to fix errors splitting a large file into many equal sized files for storage or transmission Some archive programs have self-extraction, self-installation, source volume and medium information, and package notes/description. The file extension or file header of the archive file are indicators of the file format used. Computer archive files are created by file archiver software, optical disc authoring software, and disk image software. Archive formats An archive format is the file format of an archive