U.S. Stocks End Jittery Session Flat

After switching between gains and losses, U.S. stocks ended Wednesday's choppy session essentially flat. Investors remained jittery, with uncertainty hanging over Greece's future weighing on markets. The S&P 500 ended unchanged at 2,068.53. The Dow Jones Industrial Average closed 6.62 points lower at 17,862.14. The Nasdaq Composite outperformed other indexes, ending 13.54 points, or 0.3%, higher at 4,801, largely thanks to a 2.3% gain in Apple Inc, it's biggest component.