Here are five things you must know for Tuesday, Aug. 21:

1. -- Stocks Rise, Dollar Slumps After Trump Criticizes Fed

U.S. stock futures posted modest gains on Tuesday, Aug. 21, but the dollar extended its fall after Donald Trump criticized the Federal Reserve for raising interest rates.

Contracts tied to the Dow Jones Industrial Average  rose 53 points, futures for the S&P 500  were up 5.25 points, and Nasdaq futures rose 20 points.

The dollar index, which measures the greenback against a basket of currencies, was down 0.19% to 95.54 after Trump told Reuters in an interview that he was "not thrilled" with the Federal Reserve under Chairman Jerome Powell, Trump's appointee, for raising interest rates and said the Fed should do more to help him to boost the economy.

"I'm not thrilled with his raising of interest rates, no. I'm not thrilled," Trump said, referring to Powell. Trump nominated Powell last year to replace Janet Yellen as Fed chair.

The U.S. central bank has raised interest rates twice this year and is expected to do so again when it meets in September after consumer price inflation hit 2.9% in July, the highest level in six years. Investors will be watching this week's Jackson Hole meeting of central bankers and for any response from Powell who will speak on Friday, Aug. 24.

2. -- Kohl's Highlights Tuesday's Earnings Calendar

The economic calendar in the U.S. on Tuesday is light.

Kohl's Corp. (KSS)  reported second-quarter adjusted earnings of $1.76 a share, higher than estimates of $1.64, while revenue was $4.57 billion, above forecasts of $4.27 billion.

Kohl's also raised its 2018 outlook for earnings per share but the stock fell 3% in premarket trading.

Earnings reports are also expected Tuesday from TJX Cos. (TJX) , Urban Outfitters Inc. (URBN) , Medtronic PLC (MDT) and J.M. Smucker Co. (SJM) .

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3. -- Nvidia Chips Are the Future of Gaming

Nvidia Corp. (NVDA) shares were rising 0.7% in premarket trading a day after CEO Jensen Huang delivered the keynote address at Gamescom 2018, the world's biggest gaming expo, in Cologne, Germany, and provided details about the improvements available in Nvidia's new GeForce RTX 2080 series of graphics cards.

The new cards are promised to deliver real-time ray tracing, which is a highly demanding way to portray light realistically in computer-generated graphics, to video games.

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"The real reason the shares pushed higher (up 1.2% on Monday) is not because of a Turing or ray-tracing related announcement per se, but rather, because this is the first time we've gotten a clear look at the chips that will replace the current line of Pascal-based GeForce GPUs," wrote Cramer and the AAP team. "Essentially, we now have a clearer look at what the next generation of gaming looks like and can start gauging demand for upgrades with established prices that go as high as $1,199. That is a hefty sum, but a justified price based on the significant advances Nvidia has made."

4. -- Apple Pay Now Accepted at U.S. Costco Locations

Apple Inc.'s  (AAPL) Apple Pay is now being accepted at all Costco Warehouse Corp. (COST) locations in the United States.

Costco this week activated contactless payments at all of its 750 locations across the country, according to Mac Rumors, and also was outfitting its gas stations with contactless readers.

Costco had been trialing Apple Pay at a warehouse in Issaquah, Wash., near its corporate headquarters, but only now has acceptance rolled out to all of its stores, Mac Rumors reported.

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5. -- Amazon Continues Healthcare Push Inc. (AMZN) has hired well-known cardiologist Maulik Majmudar for a new role, as it looks to move into the $3 trillion healthcare sector, CNBC reported.

Before joining Amazon, Majmudar worked as a cardiologist and associate director of the healthcare transformation lab at Massachusetts General Hospital and he lectured at MIT. At the lab, he looked at how to incorporate the latest medical technologies into the practice of medicine.

Amazon is working on many healthcare projects, CNBC noted. Among them: The company's business group is looking to sell medical supplies to hospitals and clinics; Amazon's cloud team is selling AI and other advanced technologies to healthcare companies; Amazon in June acquired online pharmacy PillPack.

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