Shipments of personal computers fell nearly 11 percent last quarter, to the shock of almost no one. Sales have been declining for so long — 14 consecutive quarters — that it is becoming harder to remember a time when PCs ruled the tech world.

The prolonged slump helps explain why so many of the leading PC makers are scrambling to continue remaking themselves in a world dominated by mobile devices operated with touch, rather than mouse clicks.

Hewlett-Packard is splitting into two entities. Lenovo has branched out into smartphones by acquiring Motorola Mobility. And, in the latest sign of the changes roiling the business, Dell, the world’s third-largest PC company by shipments, is in advanced talks to acquire EMC, the big data-storage company. Such a deal could accelerate a long-running effort by Dell to diversify its business.

Adding to that stew of uncertainty is Microsoft, the technology powerhouse that provides the software for the vast majority of PCs. In recent years, Microsoft has taken the once-unthinkable step of competing with its hardware partners, like Dell and HP, by making its own computers, starting with its Surface tablet. This week, Microsoft dived even further into the business with a laptop device, the Surface Book.