MIME encoding of RISC OS files

MIME (Multipurpose Internet Mail Extensions) defines a standard way of adding file attachments to email messages. In particular it defines "content-subtype" fields that allow for applications, WWW servers, etc. to identify particular types of data (eg, Postscript, HTML, JPEGs, etc).

In order to ensure that the set of such values is developed in an orderly, well-specified, and public manner, MIME defines a registration process which uses the Internet Assigned Numbers Authority (IANA) as a central registry for such values.

In June of 1995, ANT Limited had the registration of a new MIME content-type/subtype for the encoding of RISCOS filetypes approved by IANA. What this means is that all MIME-aware packages in the world can at least extract RISCOS attachments in email, and if they know about the application/riscos MIME type, then they will be able to extract the RISCOS-specific details as well (eg, filetype or load/exec address).

All email packages for RISCOS should use this standard, which has been published at IANA media-types since June of 1995. A local copy is shown below.

Subject: Registration of new MIME content-type/subtype

MIME type name:

MIME subtype name:

Required parameters:

Optional parameters:
name, type, load, exec, access
Encoding considerations:
Acorn RISC OS filetypes cover a wide range of file formats, some of
which are 7-bit ASCII, but mostly are 8-bit binary formats. There
are no (RISC OS imposed) limits on line lengths. Parts will typically
be encoded as 7bit or Base64.

Security considerations:
Executable images may be sent with this subtype - the user should
explicitly make the decision to run any executable, not the MUA.

Published specification:
This document. For further details, see the RISC OS Programmers
Reference Manuals, published by Acorn Computers Ltd,
ISBN 1-85250-110-3.

---------- NAME="<filename>,<filetype>"
Name parameter can give just filename, or the fully specified
filepath, with a 3 or 4 digit hex number that is the encoded
filetype of the file contained. If the filetype field is missing,
then choose a sensible default based on the encoding type.
eg, NAME="README,fff"
eg, NAME="SCSI::HardDisc.$.Mail.SpoolFile,0dc" TYPE="<filetype>"
Filetype in textual form. The remote MUA may not understand a
particular filetype (because the user does not have the relevant
editor package), and so this field can clue the user as to what
they need to run the file. This field has a maximum width of
8 bytes, and may contain spaces.
eg, TYPE="Text"
eg, TYPE="ImpDoc" LOAD=<load addr>
Load address of file, as an 8-digit hex number (32-bit word).
In the case of a filetyped file, this contains the filetype,
and part of the encoded 5-byte time-date stamp for the file
(see PRMs for more details).
eg, LOAD=&FFF01234 EXEC=<exec addr>
Execution address of file, as an 8-digit hex number (32-bit word).
In the case of a filetyped file, this contains part of the encoded
5-byte time- date stamp for the file (see PRMs for more details).
eg, EXEC=&0035FD23 ACCESS=<access byte>
This is the encoded file access bits as a 2-digit hex number (8-bit
byte). Currently only certain bit fields are defined to map to
access permissions. See PRMs for details of currently defined bit
eg, ACCESS=&02 Person & email address to contact for further information:
ANT Ltd, PO Box 300, Cambridge, CB1 2EG, UK. <>

Please contact me if you have corrections, or questions relating to this document.

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Last edit: 10th Apr 2016 at 1:55pm
(593 days ago)

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