DECtape reliability?

Eric Smith spacewar at
Thu Nov 12 12:56:54 CST 2015

On Thu, Nov 12, 2015 at 8:27 AM, Jon Elson <elson at> wrote:
> LINCtape is essentially identical to DECtape.  I think the directory format
> is different, but I think the block format is the same.

No, the block format is different, as the mark track symbols are
different. It's similar, but DECtape made improvements to it to
support full bidirectional read/write capability.  (Not all DECtape
systems actually would do reverse write. Some didn't even do reverse
read. But the format supports both.)

Also DECtape does not have a specific directory format. It depends on
what computer line you are using (12-bit, 16-bit, 18-bit, or 36-bit),
and in some cases on which operating system you are running.  Some
systems have software to access foreign DECtape logical formats; I
think the widest range of DECtape interchange software provided by DEC
was on TOPS-10.

> I think the tapes are wound in reverse order


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