如何使用FORTRAN95中用户给出的值将3x3矩阵转换为行梯形？

Question

听到我的初始代码：

  PROGRAM ROW ECHELON
  INTEGER, DIMENSION (3,3):: A
  INTEGER I,J

然后我们向用户询问值。

      PRINT*,"Enter the elements for your 3x3 matrix."
      DO I=1,3
        DO J=1,3
          READ*,A(I,J)
          ENDDO
          ENDDO

      DO I=1,3
        PRINT*,(A(I,J),J=1,3)
        ENDDO
      PRINT*
      PRINT*,"Now, we have to transform it to its row-echelon form."
      PRINT*
      IF (A(1,1)==1) THEN
      PRINT*,"We'll retain the first row since its first element is 1."
      PRINT*
      ELSEIF (A(1,1)/=1) THEN
      PRINT*,"Are there any other rows whose 1st element is 1? Press 1."
      READ*,x
      ENDIF

      IF (x==1) THEN
      GO TO 1
      ENDIF

1     IF (A(2,1)==1) THEN

然后我不知道该怎么做。

请帮忙。