多重ループ構造の例

  do i=AA,BB,CC
    do j=XX,YY,ZZ
    ...
    end do
  end do

例．行列のかけ算

program main
  !
  ! Sample program of double do-loop
  ! Cal. of C=A*B
  !  
  implicit none
  integer :: i,j,k
  real :: sum, amat(2,2), bmat(2,2), cmat(2,2)

  amat(1,1)=1.0
  amat(1,2)=2.0
  amat(2,1)=3.0
  amat(2,2)=4.0

  bmat(1,1)=5.0 ; bmat(1,2)=6.0
  bmat(2,1)=7.0 ; bmat(2,2)=8.0

  do i=1,2
    do j=1,2
      sum=0.0
      do k=1,2
        sum=sum+amat(i,k)*bmat(k,j)
      end do
      cmat(i,j)=sum
    end do
  end do

  write(*,*) 'Matrix C'
  write(*,*) cmat(1,1),cmat(1,2)
  write(*,*) cmat(2,1),cmat(2,2)

end program main

実行結果