C++多文件

文件包括#include
宏定义#define
条件编译

　　　　#if #endif

　　　　#if #else #endif

　　　　#ifndef #define #endif

全局变量 extern

main.cpp

 1 #include"myCout.h"
 2 #include"myHandle.h"
 3 #include<iostream>
 4 using namespace std;
 5 int main()
 6 {
 7     int pi = 5;
 8     double a=1.0,b=3.3;
 9     showmin(min,a,b);
10     showmax(max,a,b);
11     showtest(test,a,b);
12     cout<<"pi = "<<pi<<"
extern pi = "<<::pi<<endl;
13 #if 0 //设置为0，中间内容不编译
14     cout<<"pi = "<<::pi<<endl;
15     cout<<"pi = "<<::pi<<endl;
16     cout<<"pi = "<<::pi<<endl;
17     cout<<"pi = "<<::pi<<endl;
18     cout<<"pi = "<<::pi<<endl;
19     cout<<"pi = "<<::pi<<endl;
20     cout<<"pi = "<<::pi<<endl;
21 #endif
22     cin.get();
23     return 0;
24 }

myCout.h

 1 #ifndef _MYCOUT_H
 2 #define _MYCOUT_H
 3 
 4 typedef double funcType(double,double);
 5 extern double pi;
 6 void showmin(funcType*,double,double);
 7 void showmax(funcType*,double,double);
 8 void showtest(funcType*,double,double);
 9 
10 #endif

myCout.cpp

 1 #include "myCout.h"
 2 #include<iostream>
 3 using namespace std;
 4 //定义全局变量
 5 extern double pi = 3.14159;
 6 #if 1
 7 void showmin(funcType* fp,double a,double b)
 8 {
 9     cout<<"min = "<<fp(a,b)<<endl;
10 }
11 void showmax(funcType* fp,double a,double b)
12 {
13     cout<<"max = "<<fp(a,b)<<endl;
14 }
15 void showtest(funcType* fp,double a,double b)
16 {
17     cout<<"test= "<<fp(a,b)<<endl;
18 }
19 #endif

myHandle.h

1 #ifndef _MYHANDLE_H
2 #define _MYHANDLE_H
3 
4 double min(double,double);
5 double max(double,double);
6 double test(double,double);
7 
8 #endif

myHandle.cpp

 1 #include"myHandle.h";
 2 double min(double a,double b)
 3 {
 4     return a>b?b:a;
 5 }
 6 double max(double a,double b)
 7 {
 8         return a>b?a:b;
 9 }
10 double test(double a,double b)
11 {
12     extern double pi;
13     return pi;
14 }

运行结果