Strong earnings from big U.S. companies pushed the Dow Jones industrial average to a rare triple-digit gain Friday, but the S&P 500 index still posted its first weekly loss of the year.

Hewlett-Packard had the biggest gain in the Dow and the Standard & Poor's 500 index. It posted fiscal first-quarter earnings late Thursday that beat all forecasts, a relief after months of bad news for the computer maker. H-P rose $2.10, or 12.3 percent, to $19.20.

Cabot Oil & Gas Corp. was the S&P 500's second-best performer, jumping a day after reporting earnings that beat analysts' expectations. It rose $5.95, or 11.1 percent, to $59.81.