Example

Example Fortran 90 program:

    MODULE Triangle_Operations
     IMPLICIT NONE
    CONTAINS
     FUNCTION Area(x,y,z)
      REAL :: Area       ! function type
      REAL, INTENT( IN ) :: x, y, z
      REAL :: theta, height
      theta=ACOS((x**2+y**2-z**2)/(2.0*x*y))
      height=x*SIN(theta); Area=0.5*y*height
     END FUNCTION Area
    END MODULE Triangle_Operations

    PROGRAM Triangle
     USE Triangle_Operations
     IMPLICIT NONE
      REAL :: a, b, c, Area
      PRINT*, 'Welcome, please enter the&
             &lengths of the 3 sides.'
      READ*, a, b, c
      PRINT*,'Triangle''s area: ',Area(a,b,c)
    END PROGRAM Triangle

For more information, click here