It is a usage that has been fairly widespread in computing literature since at least the early 1970s, pre-dating OS&#x2F;2 by at least a decade and a half (possibly more).  Such abbreviations punctuated by slash have been acknowledged widely even <i>without</i> the realm of computing (and for decades longer) in quite a number of manuals of punctuation and style.  And they&#x27;re still acknowledged today.  Merriam-Webster&#x27;s <i>Pocket Guide to Punctuation</i> and <i>New Hart&#x27;s Rules</i> give examples of slash-punctuated abbreviations including N&#x2F;A, c&#x2F;o, w&#x2F;o, and A&#x2F;C.<p>The amusing thing is to see it being mis-categorized a mis-spelling based upon OS&#x2F;2 of all things.  You could at least have picked OS&#x2F;360 or something.  (-: