C.2.6. - Error handling
Syntax errors from bad grammar are noted with the offending character indicated. On the following error conditions -- dividing by zero, taking the square root of a negative number, taking the logarithm of 0 or a negative number, raising 0 to a non-positive exponent and raising a negative number to a non-integral exponent -- an error message is printed showing the index number of the current point. The offending operation is not performed and calculations continue. Other error messages may be produced by the math library routines if they have problems with your numbers.