结构体的一些形式理解

//1、struct book {int a;int b;char c;};//结构声明struct book library;//结构变量定义//上述等价于struct book {int a;int b;char c;} library;//2、struct {int a;int b;char c;} library;//不带标记//3、typedef struct complex {float real;float imag;} COMPLEX;//可以用COMPLEX来替代 struct complextypedef struct {float real;float imag;} COMPLEX;//省去了结构标志complex，此时COMPLEX代替 struct {float real;float imag;}/*实际定义结构体时，可以这样写： struct complex library； complex library; COMPLEX library; */