PROGRAM copytst
   INTEGER, PARAMETER :: M=200, N=300
   DOUBLE PRECISION :: A(M,N), C(M,N)
   EXTERNAL :: matcopy

   CALL random_number(A)                        ! init A
   CALL matcopy(m, n, A, M, C, M)               ! set C = A

   print *, 'maxdiff = ', maxval(abs(A-C))      ! should be zero

END PROGRAM copytst

SUBROUTINE matcopy(nrows, ncols, A, lda, B, ldb)
!
!  Copies nrows x ncols section of A into B
!
   INTEGER, INTENT(IN) :: nrows, ncols, lda, ldb
   DOUBLE PRECISION, INTENT(IN) :: A(lda,*)
   DOUBLE PRECISION, INTENT(OUT) :: B(ldb,*)
   INTEGER :: i, j

   DO j = 1, ncols
      DO i = 1, nrows
         B(i,j) = A(i,j)
      END DO
   END DO
END SUBROUTINE matcopy