9 track tapes and block sizes

Paul Koning paulkoning at comcast.net
Fri Oct 2 13:51:44 CDT 2020

> On Oct 2, 2020, at 1:46 PM, Chuck Guzis via cctalk <cctalk at classiccmp.org> wrote:
> On 10/1/20 11:40 PM, Warner Losh via cctalk wrote:
>> On Fri, Oct 2, 2020, 12:05 AM Tom Hunter via cctalk <cctalk at classiccmp.org>
>> wrote:
>>> I have never figured out why Bob Supnik defined the magnetic tape
>>> containers (TAP files) with the one byte padding for odd length records.
>>> This seems very odd (pun intended).   :-)
>>> Even on a machine which couldn't write 32 bit numbers (the record lenght)
>>> on odd boundaries you could write the 32 bit number as 4 individual bytes.
>>> Does anyone know the reason?
> On the .TAP files that I provide to customers, I ignore the 16-bit
> granularity and supply odd-length records as appropriate. 

You can certainly create tape container files like that, but those are not TAP format.  Instead, they are E11 format.  You should call them by their proper name.


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