PROGRAM D2R4
C	Driver for routine TRIDAG
	PARAMETER (NP=20)
	DIMENSION DIAG(NP),SUPERD(NP),SUBD(NP),RHS(NP),U(NP)
	CHARACTER TXT*3
	OPEN(UNIT=5,FILE='MATRX2.DAT',STATUS='OLD')
10	READ(5,'(A3)') TXT
	IF (TXT.EQ.'END') GOTO 99
	READ(5,*)
	READ(5,*) N
	READ(5,*)
	READ(5,*) (DIAG(K), K=1,N)
	READ(5,*)
	READ(5,*) (SUPERD(K), K=1,N-1)
	READ(5,*)
	READ(5,*) (SUBD(K), K=2,N)
	READ(5,*)
	READ(5,*) (RHS(K), K=1,N)
C	Carry out solution
	CALL TRIDAG(SUBD,DIAG,SUPERD,RHS,U,N)
	WRITE(*,*) 'The solution vector is:'
	WRITE(*,'(1X,6F12.6)') (U(K), K=1,N)
C	Test solution
	WRITE(*,*) '(matrix)*(sol''n vector) should be:'
	WRITE(*,'(1X,6F12.6)') (RHS(K), K=1,N)
	WRITE(*,*) 'Actual result is:'
	DO 11 K=1,N
		IF (K.EQ.1) THEN
			RHS(K)=DIAG(1)*U(1) + SUPERD(1)*U(2)
		ELSE IF (K.EQ.N) THEN
			RHS(K)=SUBD(N)*U(N-1) + DIAG(N)*U(N)
		ELSE
			RHS(K)=SUBD(K)*U(K-1) + DIAG(K)*U(K)
     *				+ SUPERD(K)*U(K+1)
		ENDIF
11	CONTINUE
	WRITE(*,'(1X,6F12.6)') (RHS(K), K=1,N)
	WRITE(*,*) '***********************************'
	WRITE(*,*) 'Press RETURN for next problem:'
	READ(*,*)
	GOTO 10
99	CLOSE(5)
	END