[C++知识库]学习C++的第六天（函数）

1.加法函数的实现

#include <iostream>
using namespace std;

int add(int a, int b)
{
	int sum = a + b;
	return sum;
}

int main()
{
	int c = add(123,432);
	cout << c << endl;

	system("pause");
	return 0;
}

2.值传递

#include <iostream>
using namespace std;

//定义函数，实现两数字交换
void swap(int num1,int num2)
{
	int temp;
	cout << "交换前: " << endl;
	cout << "num1 = " << num1 << endl;	//num1 =10
	cout << "num2 = " << num2 << endl;	//num2 = 20
	temp = num1;
	num1 = num2;
	num2 = temp;
	cout << "交换后: " << endl;
	cout << "num1 = " << num1 << endl;	//num1 = 20
	cout << "num2 = " << num2 << endl;	//num2 = 10
	return;//可以不写
}
int main()
{
	int a = 10;
	int b = 20;

	cout << "调用函数前" << endl;
	cout << "a = " << a << endl;	//a = 10
	cout << "b = " << b << endl;	//b = 20
	//当函数作值传递时，函数的形参发生改变，并不会影响实参
	swap(a, b);
	cout << "调用函数后" << endl;
	cout << "a = " << a << endl;	//a = 10
	cout << "b = " << b << endl;	//b = 20
	system("pause");
	return 0;
}

3.函数的声明

#include <iostream>
using namespace std;

//声明可以有多次，定义只能一次
int max(int a, int b);

int main()
{
	
	int maxnum = max(10, 20);
	cout << maxnum << endl;
	system("pause");
	return 0;
}

int max(int a, int b)
{
	return a > b ? a : b;
}

4.函数的分文件编写
(1)创建后缀名为.h的文件
(2)创建后缀名为.cpp的文件
(3)在头文件中写函数的声明
(4)在源文件中写函数的定义