c++头文件

C++程序设计(c++头文件)

Definition of a class

• In C++,separated .h and .cpp files are used to define one class
• class declaration(声明) and prototypes(原型) in that class are in the header file(.h)

• All the bodies of these function are in the source file(.cpp).

  include叫做编译预处理

示例1

a.h的代码

#ifndef A //如果没有定义宏，则定义这个宏#define Ausing namespace std;void show(){    cout<<"hello world"<<endl;}#endif // A

main.cpp的代码

 #include<iostream> #include"a.h" using namespace std; int main(){     show(); }

结果

hello world

Declarations vs. Definition

• A.cpp file is a compile unit
• only declarations are allowed to be in .h
  1.extern
  2.functionprototypes
  3.class/struct declaration
  

Tips for header

1.One class declaration per header file
2.Associated with one source file in the same prefix of name.
3.The contents of a header file is surrounded with

#ifndef#define#endif