a) They have no child.
b) They have no children.

Are both a) and b) correct? Though b) seems more common.


Question: What does mathematics have to do with programming?
Answer: Two examples that immediately come to mind are: 

functions - The idea of applying a transformation to input variables to produce an output variable is strongly rooted in mathematics. The notion of passing a function around as a parameter to another function even more so. In general, the notion of abstract thinking associated with programing parallels mathematics quite closely.

bitMasks - This common programming approach to solving problems requires at least a basic understanding of boolean algebra to even grasp the concept.