????11???????????漲??????ó?????Щ????????????????????б??н??г???????????????????????????????????????????????á?????????????????????????const???????????????????????????????б??н??г??????????????????????????н??и?????????

????12????????????????????????????????????￡??????????????????????б?????????

????13?????????????????????????????????????????????????磺A a;??????????????????A a(37);????????????????????

????14?????????ж??幹????????????????????????????????????

????15????????ε?????????????????β???????????????????????????磺

class Sales_item{
         public:
                   sales_item(const std::string &book=””):isbn(book)??unit(0)??revenue(0.0){}
                   void same_isbn(Sales_item si);
};
//???????????
Sales_item item;
Item.same_isbn(“123556”);
//?????sales_item????βε????????????????????????same_isbn????Ρ???????????????????????????????????????????????expl//icit??explicit??????????????????????????????????????????

????16???????????????????????

????17??????????????????static????????????????static??????????????????????????????????????static?????????????????const?????const???????????ú???????????????????????static ???????κζ???static??????????麯????static????????????????????????????????????????????????????á?

????18??static??????????this?βΣ????????????????????static????????????????÷?static?????

????19????static????????????????static?д?????????????????????

????20??static??????????????????????????????г??????static???????????????????????????????????????????г????????static???????????????????????????????????????

????21??const static????????????????????????г?????????????????????????????????ж??塣????????????????????????????岻???????????

????22??static?????????????????Σ??????????????????

????23??static?????????????????????????????????磺

class Bar{
         public:
         private:
                   static Bar men1;//ok
                   Bar * men2;//ok
                   Bar men3;//error
};