Who was the president in the year of 1989?

This depends on the organization/country. See related questions.

US: Ronald Reagan until January 20, followed by George Hebert Walker Bush.

The 40th President of the United States was Ronald Reagan. President Reagan held office from January 20, 1985 to January 20, 1989

The 41st President of the United States was George H. W. Bush from January 20, 1989 to January 20, 1993

Ronald Reagan's presidency ended and George H. W. Bush's began on January 20 of that year.