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Compressed files

Often files which can be fetched using anonymous FTP have been compressed in some way.

Windows files may be compressed and need uncompressing before use. The type of compression is often (but not always) signalled by a special filename extension (for instance .zip). The principal unpacking utility on MCS Windows is Winzip (click on Start, move to Programs and Information, then to Utilities and Accessories, and click on Winzip). It has its own Help system.

Windows files may also be self-extracting archives (names ending in .exe) which need to be "run" (by double-clicking) to extract the individual files. You should be careful about files of this type unless you know exaclty where they have come from.

Macintosh files may be compressed; the Fetch program is usually configured to uncompress such files as they arrive, so no special separate stage is needed. Sometimes extra unpacking utilities (Stuffit Expander, for instance) may be needed, or the file may arrive as a "self-expanding archive" (name ending in .sea) which can be expanded simply by double-clicking on it.

In Unix, compressed files can be recognised by the name which usually ends in .gz or .Z. These files should be fetched in binary mode, and then uncompressed using the Unix uncompress or gunzip utility (see the man pages). The file may also be a tar file, in which case the tar utility is needed after the file has been uncompressed (see man tar).

Some details of special formats are also on the Desktop Services web pages.