macRes
macRes is a term that refers to the resource fork of a file on classic Mac OS operating systems. Files on classic Mac OS had two distinct parts: the data fork and the resource fork. The data fork contained the actual content of the file, such as the text of a document or the pixels of an image. The resource fork, on the other hand, stored metadata and user interface elements related to the file.
These resources could include things like icons, menus, dialog boxes, sounds, and even small snippets of executable
When files were transferred between different operating systems or through certain network protocols, the resource fork