RFC 42 (rfc42) - Page 2 of 3


Message Data Types



Alternative Format: Original Text Document



RFC 42                     Message Data Types                 March 1970


   better names.  In general, X and Y will perform transformations on
   the data, e.g., change character sets or number formats.  As network
   usage grows, X and Y might become table driven with the table
   specified by the user.

   Standard Types and Local Types:

   We propose to distinguish between two kinds of message data types:
   standard and local.

   Since our two transformation programs cannot be expected to perform a
   transformation between every possible data representation and the
   data representation of the machine they are running on, and also
   since the addition of a data representation should not necessarily
   involve a change to X or Y, we propose that only a fixed number of
   message types have meaning throughout the network.  These are
   standard types.

   There are two classes of local types: MYLOCAL and YOURLOCAL. A
   message type MYLOCAL n implies: this is type n of the set of types of
   the sending host.  YOURLOCAL n implies: this is type n of the set of
   types of the receiving host.

   Conventions:

   A possible implementation of standard and local types is to define
   standard type 0 to be YOURLOCAL and standard type 1 to be MYLOCAL. In
   these cases, the second byte would be the local type number.

   Local type 0 would mean user-specified, i.e., the message contents
   are unchanged and unchecked.  Installations would define their own
   local type numbers and these would normally be available from the
   Network Information Center.

   Thus initially, all messages sent to currently running programs will
   be type 0, n and all messages received from currently running
   programs will be type 1, n where n is the local type number of the
   character set of the installation.

   Examples of Possible Standard Types:

        0.     YOURLOCAL
        1.     MYLOCAL
        2.     U.S. Ascii
        3.     EBCDIC
        4.     Mod 33 TTY Ascii





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