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Information about common filetypes, and how to decode them.

Identifying formats

You may download from the Internet or receive via email files in a variety of formats. Some are encoded to avoid problems with bit patterns which cannot reliably be transferred across networks. Others are compressed to save time and disk space.

Very often you can tell what special format has been used for a file because it has a three-letter extension to its filename, identifying the format.

When you download a file, or receive it as an email attachment, you should be aware of the risk of computer viruses which often propagate by these means. Never open such a file (by double-clicking, for instance) without putting it through a virus checker first.

Uuencoded files

A special format which does not fit the above scheme is "uuencoding". People sometimes send uuencoded material in the body of an email message. The message will characteristically include a line like

begin 644

You need to save the message, strip the plain text from the front, and put it through a 'uudecode' program.

On a Managed Cluster PC, the WinZip program can process uuencoded files; on a Mac, use StuffIt Expander. If a uuencoded file arrives as an attachment, it can be fed directly to one of these programs.

Macintosh files in special formats

If you fetch a file to a Managed Cluster Macintosh using the Fetch program, you will usually find that files which have been compressed or encoded are automatically uncompressed or decoded by the Fetch program.

However, if you have a file with extension .sit, .zip or .hqx (Binhex) which has not been expanded when you fetched it, you need Stuffit Expander, which can be found under Applications > Utilities. Other less common formats handled by Stuffit Expander are .cpt, .bin (MacBinary), .gz,.arc,.z and .tar.

Files ending in .sea are 'self-extracting archives', and all you need is to double-click on the file, which will then normally expand itself into a folder.

If the file you have fetched is a Macintosh application, you may need to go through an installation process before it is ready for use. The application folder will usually contain a README file with suitable instructions. Note that you cannot install your own applications on the UIS applications space; they will have to be in your own filespace.

Other file formats you may sometimes see on a Macintosh are the graphical formats .jpeg, .tiff, .pict, .eps, .gif and .png. Most of these can be handled by Graphic Converter.

Windows files in special formats

Many files fetched from software or other archives will be in ZIP format, identified by a filename extension .zip. The principal program for decoding this and many other formats is WinZip, which can be found on the Managed Cluster PCs under Utilities. Formats decoded by WinZip include .tar,.z,.gz,.taz, and .tgz. Additionally it can decode MIME files, uuencoded files (see above) and Macintosh HQZX files.

If the file you have fetched is a Windows application, you may need to go through an installation process before it is ready for use. The application folder will usually contain a README file with suitable instructions. Note that you cannot install your own applications on the UIS applications space; they will have to be in your own filespace.

Other special format files you may encounter on a PC include the graphics formats, GIF, JPEG, JPG, TIFF, EPS, PICT and PNG. Most of these can be handled by Photoshop, which is on the Managed Cluster PCs under Graphics and Presentation.

 

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