PROGRAM ex5_7 
IMPLICIT NONE 
REAL :: r = 0.0E0, x, d = 1.0E-5 
DO 
PRINT *, 'Input a positive real number: ' 
READ *, r 
IF ( r > 0.0E0 ) EXIT 
END DO 
x = r 
DO WHILE ( ABS( x ** 2 - r ) / r > d ) 
PRINT *, '途中のx=',x
x = 0.5E0 * ( x + r / x ) 
END DO 
PRINT '( 1X, E12.5 )', x 
END PROGRAM ex5_7