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 A
using 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