That approach has its own problems. Working Model, a physics simulator from Knowledge Revolution (Macintosh, mid-1990s) used a copy protection scheme where it asked for the last word from some page in the manual. Unfortunately, after the copy protection was set up, but before the product shipped, someone made a small change to the manual that caused repagination. Page numbers in the first two thirds of the manual still worked, so the product seemed to be OK. Those in the last third didn't. Fortunately, you could just restart the program and try again, hoping for an early page number.
When we had Sun workstations at Ford Aerospace in the early 1980s, we had several software packages which were locked to specific CPU IDs. Sun CPU boards of the era were not very reliable. Every time we replaced a CPU board, the paid software packages stopped working until we got new serial-number stamped versions, on magnetic tape, of each package. This usually meant about a month of downtime for the workstation. That's the earliest example I have.
Well, you can go back to at least the Middle Ages in Europe, when valuable books were sometimes chained in place in monasteries or libraries to keep people from running off with them.
I would just like to take a break from the very literal responses (I admit I immediately thought "that's not digital" too) to say that this made me laugh. :-)
Physical books are not digital, therefore cannot have DRM. Also, DRM is about managing the "rights" of the copyrighted material's producer - not the end user. Chaining books in a public place maintains the book from being physically stolen, taken from the public's possession.
That's not DRM though. Nobody stopped you from making a copy without the chain. (apart from the fact that it would take ages and be quite expensive a the time) Actual theft protection is not DRM.
Right DRM is not copy protection. DRM is about keeping legitimate buyers from exercising free trade. You can't buy up a dozen games on steam, for example, and resell the games on. Of course people still do, but that's what steam's drm is intended to quell. You can't take a bluray, make a copy, upload it to somebody's email for a price, and destroy the original. This is a perfectly honest thing to do, it's super easy to do, but it's incredibly risky in the US to do it.
