ArcFS is an archiver for RISC OS, claimed to have similar functions to Spark and to have a free read-only (de-archiver) version, so that you don't have to buy anything to open archives created in the ArcFS format.
The (rather over-used) .arc file extension is used, even though the format is not compatible with the various other formats for various other platforms that have also used this extension. On RISC OS systems, files in this format typically have a filetype of 3FB ("ArcFSArc"). Prior to the official filetype allocation sometime around 1993, filetype DDC ("Archive") was used (although DDC was also used for other file formats such as ZIP).
ArcFS files normally begin with
41 72 63 68 69 76 65 00 ("
Another possible signature suggested by the file command is
1A 61 72 63 68 69 76 65.
- APDL Public Domain CD 2 contains many files in ArcFS format
- http://arcade.demon.co.uk/filepages/file77.htm → MacScrn