SAN FRANCISCO — Battling declining demand for personal computers, Hewlett-Packard Co., the largest maker of PCs, reported lower quarterly earnings Thursday. They were significantly higher than analysts expected, however.

‘‘The turnaround is starting to gain traction as a result of the actions we took in 2012 to lay the foundation of HP’s future,’’ said Meg Whitman, chief executive. ‘‘I feel good about the rest of the year.’’