C Created:  Joe Zachary, October 26, 1992
C Modified:

C This function takes a real number "X" as an argument and computes
C its square root using an approximation algorithm.

      REAL FUNCTION SROOT (X, PRECISION)

      IMPLICIT NONE
      REAL X, GUESS, PRECISION

      GUESS = 1

      DO WHILE (ABS(X - GUESS*GUESS) .GT. PRECISION)
        GUESS = (GUESS + X/GUESS) / 2
      ENDDO

      SROOT = GUESS
      RETURN
      END



      PROGRAM TEST

      IMPLICIT NONE
      REAL SROOT, X

      PRINT *, 'Please enter a positive real number'
      READ *, X

      PRINT *, 'The square root is ', SROOT(X, .00001)

      STOP
      END