What is a forked file structure?
Note: This document applies primarily to Mac OS 9 and earlier. In Mac OS X, files with multiple forks are supported, but uncommon. For most native applications, the resource information is stored differently, and documents typically don't require resource forks at all.
A forked file structure is a method of storing information unique to Mac OS. Every Mac OS file consists of at least one of two separate pieces of information, or forks: a data fork and often a resource fork. A file's data fork holds raw data in an organized but relatively unintelligible format. The resource fork consists of all the interfaces, dialog boxes, warning boxes, and graphical user interface (GUI) information necessary to correctly format and present the data.
Not every Mac file has both a resource and a data fork. Many files, such as those created by word processors and spreadsheet programs, are entirely data; all of the extra formatting and GUI information resides in the application that made the file.
Because of the forked file structure, it is often necessary to encode Mac files before transferring them on the Internet or to other operating systems. Without this encoding, the files' resource forks will be stripped away, which will ruin any classic application, and certain Mac-only documents as well. If you are transferring files used on multiple platforms (e.g., GIF images, Microsoft Word documents, or HTML files) it isn't necessary to encode them first; but otherwise, use a program such as DropStuff to protect them.
Last modified on March 31, 2010.
