ARCHIMEDES ISO 9660 extension

This article covers an ISO 9660 extension that contains metadata specific to Acorn / Archimedes / RISC OS systems.

Format details

The extension is a 32-byte data element located in the "system use" area of each directory record. It begins with the signature "ARCHIMEDES".

According to a cdrtools patch [1], the format is:

0-9   "ARCHIMEDES"
10-13 Load address
14-17 Execution address
18-21 Attributes
22-31 Reserved

The load/execution/attributes fields are 32-bit little-endian integers. Following a RISC OS convention, the load/execution fields usually contain the file type and a timestamp. It is comparable to the ZIP "AC" extensible data field, for example.

Attributes bit 0x100 indicates that the original filename began with a "!" character.

Sample files

The extension is common on RISC OS CD-ROMs.

• APDL Public Domain CD 2 → APDL_PD2A.iso