DECtape ancestry

[Paul Koning]

> On Mar 20, 2021, at 4:07 PM, Kyle Owen via cctalk <cctalk at classiccmp.org> wrote:
> 
> Why did DEC not use the LINCtape format for the PDP-8? I assume maintaining
> format compatibility between their low, mid, and high range systems was
> important to them? I suppose there was no other good solution to
> transferring large files across different DEC platforms than to use
> magnetic tape...so I may have answered my own question here.
> 
> Kyle

Speculating here since I have no direct knowledge: the DECtape format allows read and write in either direction, while LINCtape only allows read and write forward.  The bidirectional I/O capability was part of DECtape format from the start, and I suspect the desire was to keep that.

Also, the DECtape format (ignoring the funny bit order in the PDP-1 case) is the same across all models except for the block size and count in the PDP-8 case.  Chances are the desire was to reuse all that design.

	paul