CrossDOS is a file system handler for accessing FAT formatted media on Amiga computers.
[1] Its function was to allow working with disks formatted for PCs and Atari STs (and others).
However, the versions of CrossDOS bundled with AmigaOS did not support long filenames, an extension to FAT that was introduced with Microsoft's Windows 95.
CrossDOS was originally developed as a stand-alone commercial product by Consultron, which was available for AmigaOS 1.2 and 1.3.
The bundled CrossDOS replaced an obscure tool in earlier versions of AmigaOS that could access FAT formatted disks on a secondary floppy disk drive only (this tool was not a complete file system but a user program to read files from a FAT formatted disk).