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;
}

---

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;
}

 

---

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;
}

 

---

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;
}

---

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;
}

---

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;
}