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AppleSingle and AppleDouble formats
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<p>AppleSingle Format and AppleDouble Format are <a href="/facts/File_format/qrXbwJaH">file formats</a> developed by <a href="/facts/Apple_Computer/oTJYta3k">Apple Computer</a> to store <a href="/facts/Mac_OS/EkobAhow">Mac OS</a> <a href="/facts/Resource_fork/zVnSVjbb">"dual-forked" files</a> on the <a href="/facts/Unix/0pNL2seI">Unix</a> filesystem being used in <a href="/facts/A%2fUX/EzdufrHs">A/UX</a>, the Macintosh platform's first <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> <a href="/facts/Operating_system/8XTuvMh2">operating system</a>. AppleSingle combined both file forks and the related <a href="/facts/Macintosh_Finder/LD3gHLDo">Finder</a> meta-file information into a single file, whereas AppleDouble stored them as two separate files. Support for the formats was later added to Unix software such as <a href="/facts/Network_File_System_(protocol)/jWRRALVo">NFS</a> and <a href="/facts/Macintosh_Application_Environment/JUnvtS2z">MAE</a>, but they saw little use outside this small market. </p><p>AppleSingle is similar in concept to the more popular <a href="/facts/MacBinary/1dIfr23C">MacBinary</a> format, in that the resource and data forks are combined with a header containing the Finder information. In fact, the format is so similar, it seemed there was no reason why Apple did not simply use MacBinary instead, which by that point was widely known and used. Some not-so-obvious reasons are explained in an Internet Draft. The format was later assigned the <a href="/facts/MIME_type/A31N5Fwj">MIME type</a> application/applefile. </p><p>AppleDouble leaves the data fork in its original format, allowing it to be edited by normal Unix utilities. The resource fork and Finder information, both proprietary and lacking editors under Unix, were combined into a second file. A MIME type was also assigned to AppleDouble, multipart/appledouble. For sending to an AppleDouble un-aware system, the file was generally encoded using <a href="/facts/Base64/xIvVm33q">Base64</a>, as opposed to being converted to AppleSingle. </p>