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.
... Michigan. It is the county seat of Calhoun County. It is the world headquarters of Kellogg Company[?] (cereal), manufacturer of corn flakes and other breakfast cereals. ...