The two standards below reflect the current Fortran implementations . Perhaps the most significant development in the early history of FORTRAN was the decision by the American Standards Association ( now ANSI ) to form a committee to develop an `` American Standard Fortran . '' The resulting two standards , approved in March 1966 , defined two languages , FORTRAN ( based on FORTRAN IV , which had served as a de facto standard ) , and Basic FORTRAN ( based on FORTRAN II , but stripped of its machine-dependent features ) .