It is a usage that has been fairly widespread in computing literature since at least the early 1970s, pre-dating OS/2 by at least a decade and a half (possibly

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