What precisely “post-PC” means will be tough to assess until a decade or so from now, when the change has been fully digested. At the moment, the most concrete meaning is that people are using different devices--tablets, mostly--for activities that once were done on personal computers.

But that shift also means device purchasing trends are changing, so the most significant immediate consequence of the post-PC era is a shift in user preferences for appliances. Over time, the phrase is likely to take on new meanings, as other end user behavioral changes occur, and as the framework of computing shifts to a cloud-based mode.

In fact, since several changes seem to be happening at once, it is harder to describe the ultimate impact. Though cloud computing, apps, tablets and smartphones might be considered distinct developments, they probably are not, and someday might be seen as related to some larger trend for which we will have a commonly accepted name. For now, all we can say is that things are changing.

Tablet ownership in Western Europe, for example,  is set to quadruple in the next five years, according to Forrester Research analyst Reineke Reitsma.

The percentage of European online adults who own a tablet will increase from 14 percent in 2012 to 55 percent in 2017, according to Forrester Research forecasts, after doubling in 2012.

So far, we remain in the early adopter phase, though. Today, tablets are most popular with those 18 to 24, with 25 percent of online consumers in that age group now owning a tablet. Tablet ownership also skews in the direction of technology enthusiasts, at the moment.

Also, up to this point, income has been an issue. About 24 percent of high-income European online consumers have a tablet, compared with 15 percent of online low-income consumers. But that will change as newer form factors bearing smaller price tags are made available by a greater range of suppliers.

The ways tablets get used also hints at the direction of the post-PC trend. At least so far, the tablet is a supplement or complement to other Internet-using devices.

Many tablet owners also own a laptop and a smartphone, for example. European online consumers mostly use their tablets in their living rooms, for example. They use their smartphones when out and about and their notebooks for work. At least so far, the tablet is a shared-use device.

About 66 percent of tablet owners share their tablet with partners, co-workers, children, or friends, Forrester Research says. That could change with time. PCs once were shared devices in homes, but these days are more likely to be personal devices as are smartphones.