c This is the way that Fortran 77 put comments in.
      ! Fortran 90 also allows this way
      ! Fortran 90 also allows the Fortran 77 method
      ! g77 also allows both

      PROGRAM HelloWorld
      ! This program prints out hello world
      PRINT *, " Hello World "
      ! This is an alternative way to get Fortran to print Hello World
      WRITE(6,*) " Hello World "
      ! Yet anotherfrotran 77  way to do it is
      WRITE(6,1)
 1    FORMAT(" Hello World ") 
      ! However statement labels and specified input
      ! channels are cumbersome. The Fortran 90 style is 
      WRITE(UNIT=*, FMT=*) "Hello World" 
      ! or
      WRITE(UNIT=*, FMT="(A)") " Hello World" ! Best way for this example
      END PROGRAM HelloWorld