When exchanging files with Windows users, itÆs a good idea to use DOS-style three-letter extensions on your filenames, such as .doc for Word files, .tif for TIFF images, .qxd for Quark XPress files, etc. Most applications that exist on both platforms will understand the other platformÆs files, but e-mail applications will not recognise which application opens which file. ItÆs also a good idea to get in practise using these extensions, because Mac OS X will require them when it is released a year from now.