It&#x27;s not an old file. It&#x27;s a new file resulting from running OCR on a PDF of a physical manual. Clipping off the filename in the original URL, you&#x27;ll find a directory [1] with an explanation in the README [2]<p>[1] <a href="http:&#x2F;&#x2F;www.tuhs.org&#x2F;Archive&#x2F;PDP-11&#x2F;Distributions&#x2F;research&#x2F;McIlroy_v0&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.tuhs.org&#x2F;Archive&#x2F;PDP-11&#x2F;Distributions&#x2F;research&#x2F;Mc...</a>
[2] <a href="http:&#x2F;&#x2F;www.tuhs.org&#x2F;Archive&#x2F;PDP-11&#x2F;Distributions&#x2F;research&#x2F;McIlroy_v0&#x2F;Readme" rel="nofollow">http:&#x2F;&#x2F;www.tuhs.org&#x2F;Archive&#x2F;PDP-11&#x2F;Distributions&#x2F;research&#x2F;Mc...</a>