Stocks maintained slight gains as investors looked toward a speech from Federal Reserve Chair Janet Yellen Friday afternoon.

The S&P 500 rose 0.3%, the Dow Jones Industrial Average gained 0.22%, and the Nasdaq increased 0.52%.

Wall Street may get more clues on monetary policy from Fed Chair Janet Yellen's appearance at Harvard on Friday, when she's interviewed by Professor Greg Mankiw and receives the Radcliffe Medal. It's unlikely she will say anything explicit about interest rates, though investors will look for hints.

"Even though Fed Chair Janet Yellen is speaking today (and supposedly on interest rates in a discussion with Harvard professor Greg Mankiw), she has a major policy speech planned for June 6, and as such, it seems unlikely that she would pre-announce any significant changes to her outlook," said Christopher Vecchio, currency analyst at DailyFX.

The U.S. economy grew at a pace of 0.8% in the first quarter, above a previous estimate showing 0.5% growth. However, the revision was slightly lower than an expected 0.9%. A stronger U.S. dollar, weaker global growth and chaotic financial markets weighed on the U.S. economy, though not as badly as initially feared. Personal consumption was unchanged at 1.9%, its lowest in three quarters. 

"No doubt an upward revision of any size helps alleviate the pain of a weaker-than-expected first round Q1 growth report, but a minimal increase does little to reinforce optimism of better times ahead," said Lindsey Piegza, chief economist at Stifel. "Nevertheless, the hawks at the FOMC ... will no doubt highlight any additional upward revision as support to their thesis of fundamental strength in the U.S. economy."

Crude oil prices moved further away from the $50-mark on Friday after briefly topping the level for the first time since in seven months a day earlier. Crude got a pick-up earlier in the week on more signs reduced U.S. production was eating into domestic inventories.

West Texas Intermediate crude oil was down 0.6% to $49.17 a barrel on Friday morning.

Thermo Fisher (TMO) - Get Report agreed to buy FEICo. FEIC in an all-cash deal worth $4.2 billion. Thermo agreed to pay $107.50 a share for FEIC, representing a 14% premium to Thursday's close. The acquisition is expected to close in early 2017. FEI shares jumped 14%.

Thermo Fisher is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells TMO? Learn more now.

A U.S. jury ruled in Alphabet's (GOOGL) - Get Report favor on Thursday evening after finding that Google's use of Java programming in Android was in fair use. Oracle (ORCL) - Get Report had brought the lawsuit against Google, arguing the use of the software infringed upon their patents. The court battle has been ongoing since 2010 and Oracle expects to appeal the decision.

Alphabet is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells GOOGL? Learn more now.

GameStop (GME) - Get Report sank 4% after posting disappointing same-store sales in its first quarter. The video-game retailer reported a 4.4% decline in sales to $1.97 billion, while sales in stores open at least a year fell 6.2% compared to an 8.6% increase a year earlier.

Palo Alto Networks (PANW) - Get Report slumped 12% after forecasting slower growth in its fourth quarter. The online security company said it expects fourth-quarter earnings between 48 cents and 50 cents a share, slightly weaker than analysts had expected. The company has "anticipated for some time that seasonality would evolve in the business," chief financial officer Steffan Tomlinson said in a statement.