Tape imaging

Chuck Guzis cclist at sydex.com
Thu Aug 11 01:38:17 CDT 2016

On 08/10/2016 10:40 PM, jim stephens wrote:

> The Microdata M1621 Ascii is a weird ascii with the high order bit on
> in the character set, similar to EBCDIC, so the representation is 
> important.  I think the OS you are on dictates that to some degree
> as far as sequencing the records as I did initially, but it is all
> moved to TAP once that is done.

Just like the PRIME PRIMOS convention.  Makes it easier to pick out
strings from a MAGSAV archive.

> No real concensus on metadata, though I think there was discussion
> about dumping it after the logical EOT, either two or three tape
> marks in the container, either TAP or AWS tape format.

There is an EOM record in the .tap format = 0xffffffff - all ones.   No
need for extra filemarks.  After that just add standard 32-bit bytecount
headers and trailers to bracket each set of metadata and put whatever
you want between them.

Add a final EOM flag just for completeness' sake.

My gripe with .tap has been mentioned before--there's no standard way to
specify the *type* of error encountered--just that the high-order bit is
an error flag with  the lower 24 bits corresponding to the length of the
error block. Perhaps the unspecified 7 bits between the error flag and
the length could be put to this purpose.

Again, we're caught with the problem of those who just want data and
those who want more than the raw data.


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