April 27 (Reuters) - The S&P 500 and the Nasdaq opened slightly higher on Tuesday as investors geared up for earnings reports from Microsoft and Alphabet, while awaiting cues from the Federal Reserve on its monetary policy stance. The S&P 500 opened higher by 0.63 points, or 0.02%, at 4,188.25, while the Nasdaq Composite gained 32.14 points, or 0.23%, to 14,170.91 at the opening bell. The Dow Jones Industrial Average fell 49.44 points, or 0.15%, at the open to 33,932.13. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Anil D’Silva)