In the Numerical Recipes in section 5.7.- Numerical derivatives the choice of the step size $h$ in the numerical derivative should lead to a difference between $x$ and $x+h$ representable by an exact number. In C, the program steps are:
temp = x + h h = temp - x
Question: What is the meaning of these steps?
Question: How can choose $h$ as an "exact" number in Matlab?