1、函数定义

#include <iostream>
using namespace std;int add(int num1, int num2) {int sum = num1 + num2;return sum;
}int main() {system("pause");return 0;
}

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2、函数的调用

#include <iostream>
using namespace std;int add(int num1, int num2) {int sum = num1 + num2;return sum;
}int main() {int a = 10;int b = 20;int sum = add(a, b);cout << sum << endl;system("pause");return 0;
}

 

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3、值传递

#include <iostream>
using namespace std;void swap(int num1, int num2) {cout << "交换前" << endl;cout << "num1=" << num1 << endl;cout << "num2=" << num2 << endl;int temp = num1;num1 = num2;num2 = temp;cout << "交换后" << endl;cout << "num1=" << num1 << endl;cout << "num2=" << num2 << endl;
}int main() {int a = 10;int b = 20;swap(a, b);cout << "a=" <<a<< endl;cout << "b=" << b << endl;system("pause");return 0;
}

 

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4、函数的常见样式

#include <iostream>
using namespace std;//1、无参无返
void test01() {cout << "this is test01" << endl;
}//2、有参无返
void test02(int a) {cout << "this is test02 a = " << a << endl;
}//3、无参有返
int test03() {cout << "this is test03" << endl;return 1000;
}//4、有参有返
int test04(int a) {cout << "this is test04 a = " << a << endl;return a;
}int main() {//无参无返的函数调用test01();//有参无返的函数调用test02(100);//无参有返的函数调用int num1=test03();cout << "num1 = " << num1 << endl;//有参有返的函数调用int num2=test04(10000);cout << "num2 = " << num2 << endl;system("pause");return 0;
}

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5、函数声明 

#include <iostream>
using namespace std;int max(int a, int b);int main() {int a = 10;int b = 20;cout << max(a, b) << endl;system("pause");return 0;
}int max(int a, int b) {return a > b ? a : b;
}

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6、函数的分文件编写 

函数分文件编写一般有4个步骤
1.创建后级名为.h的头文件
2.创建后缀名为.cpp的源文件
3.在头文件中写函数的声明
4.源文件中写函数的定义

 

 swap.h

#include <iostream>
using namespace std;void swap(int a, int b);

swap.cpp

#include "swap.h"void swap(int a, int b) {int temp = a;a = b;b = temp;cout << "a = " << a << endl;cout << "b = " << b << endl;}

main.cpp

#include <iostream>
using namespace std;
#include "swap.h"int main() {int a = 10;int b = 20;swap(a, b);system("pause");return 0;
}