A bullish outlook from Microsoft and other upbeat earnings from Caterpillar and Honeywell helped sentiment.
Investors were also digesting a proposed stimulus plan from Washington and expecting more rate cuts next week when the Federal Reserve meets.
Less than an hour after the opening bell, the S&P 500 was up 0.75 per cent at 1,362.20 and had traded between a high of 1,368.56 (up 1.2 per cent) and a low of 1,357.32 (up 0.4 per cent on the day). For the week, the S&P is up 2.8 per cent, clipping its overall loss this month to 7.2 per cent.
The Nasdaq Composite was up 0.9 per cent at 2,383.22, a gain of 1.8 per cent this week and trimming its loss this month to 10 per cent.
The mood in technology was boosted late on Thursday, when Microsoft beat fiscal second quarter earnings estimates and raised guidance. The stock was up 2.6 per cent at $34.12, after a rise of 4.1 per cent to $33.25 in regular trade on Thursday.
The Dow Jones Industrial Average was 0.5 per cent higher at 12,445.35. The Dow has risen 2.9 per cent this week, paring its loss since the start of the year to a fall of 6.2 per cent.