In computer science's object-oriented programming, class variables (static fields) contain information which is associated with all instances of a class. If all tanks have one cannon, then it is not necessary to specify, in an instance variable for each tank object, that each tank has only one cannon; rather, one can simply define a class variable which does this and thus all instances of the class will share the variable.
... is $60,209, and the median income for a family is $67,375. Males have a median income of $50,715 versus $34,301 for females. The per capita income for the town is $23,233. ...