Answer from cs61c-fx (maryam nili 13888544) for Question 1
some one can use this security holes to crash computers,by 
playing with floats(over or underflow problems) for instance.it can be solved by using separate integers ans floating-point registers which make the process very slow,
specially in divisions.to make it slow division faster,Newton's iteration can be used,where division is recast as finding ther zwro of a function to find the reciprocal 1/x, which is ther multiplied by the other operand.