PROGRAM subroutine_madness

IMPLICIT NONE
INTEGER :: n
DOUBLE PRECISION, POINTER,  DIMENSION (:) :: xfct
DOUBLE PRECISION, POINTER,  DIMENSION (:) :: yfct
DOUBLE PRECISION                :: sum, sumprod
DOUBLE PRECISION                :: sx, sy, sx2, sy2, sxy, roh

print*, 'n'
READ (5,*) n
print*, 'n', n

ALLOCATE (xfct(n),yfct(n))
CALL  lies (xfct,n)
CALL  lies (yfct,n)
CALL  summe (xfct,n,sx)
CALL  summe (yfct,n,sy)
CALL  sumproduct (xfct,xfct,n,sx2)
CALL  sumproduct (yfct,yfct,n,sy2)
CALL  sumproduct (xfct,yfct,n,sxy)

roh=(sxy-sx*sy)/( ((sx2-sx*sx)*(sy2-sy*sy))**(0.5D0) )
PRINT*, roh
DEALLOCATE(xfct,yfct)
END PROGRAM

!===================================

SUBROUTINE lies (xfct,n)

IMPLICIT NONE
INTEGER :: n,i
DOUBLE PRECISION, DIMENSION (n) :: xfct

print*, 'Messwerte'
DO i=1,n
  READ(5,*) xfct(i)
END DO

END SUBROUTINE lies

!==================================

SUBROUTINE summe (xfct,n,sum)

IMPLICIT NONE
INTEGER :: n,i
DOUBLE PRECISION, DIMENSION (n) :: xfct
DOUBLE PRECISION :: sum

SUM=0.D0

DO i=1,n
   SUM = SUM + xfct(i)
END DO

SUM = SUM/n

END SUBROUTINE summe

!==================================

SUBROUTINE sumproduct(xfct,yfct,n,sumprod)

IMPLICIT NONE
INTEGER :: n,i
DOUBLE PRECISION, DIMENSION (n) :: xfct
DOUBLE PRECISION, DIMENSION (n) :: yfct
DOUBLE PRECISION :: sumprod

sumprod = 0.D0

DO i=1,n
  sumprod=sumprod + xfct(i)*yfct(i)
END DO

sumprod=sumprod/n
END SUBROUTINE