返回值類型 函數(shù)名(參數(shù)列表)
{
	函數(shù)體語句;
	
	return表達(dá)式;
}

函數(shù)名(參數(shù))

#include<iostream>
using namespace std;

//返回值類型 函數(shù)名 (參數(shù)列表){ 函數(shù)體語句 ; return表達(dá)式;}

//定義一個(gè)兩整型數(shù)相加的函數(shù)
int add(int num1, int num2)//num1和num2并沒有真實(shí)數(shù)據(jù)，只是一個(gè)形式上的參數(shù)，簡(jiǎn)稱形參
{
	int sum = num1 + num2;
	return sum;
}

int main()
{	//main函數(shù)中調(diào)用add函數(shù)
	int a = 3, b = 4;
	
	//函數(shù)調(diào)用語法：函數(shù)名稱(參數(shù))
	int c = add(a, b); //a和b是真實(shí)的數(shù)據(jù)，稱為實(shí)際參數(shù)，簡(jiǎn)稱實(shí)參
	cout << c << endl;

	system("pause");
	return 0;
}

#include<iostream>
using namespace std;

//定義一個(gè)交換數(shù)字的函數(shù)
//因?yàn)楹瘮?shù)沒有返回值，所以可以定義函數(shù)類型為void-無類型。
void swap(int num1,int num2)
{
	cout << "交換前：" << num1 << "  " << num2 << endl;
	int temp = num1;
	num1 = num2;
	num2 = temp;
	cout << "交換后：" << num1 << "  " << num2 << endl;
}
int main()
{	
	int a = 10, b = 20;
	swap(a, b);
	//形參的改變并不影響實(shí)參本身
	cout << "a = " << a << "\n" << "b = " << b  << endl;
	system("pause");
	return 0;
}

#include<iostream>
using namespace std;

//1.無參無返
void test01()
{
	cout << "無參無返" << endl;
}
//2.有參無返
void test02(int num1,int num2)
{
	cout << "有參無返" << num1 << num2 << endl;
}
//3.無參有返
int test03()
{
	cout << "無參有返 " ;
	return 1000;
}
//4.有參有返
int test04(int num)
{
	cout << "有參有返 " ;
	return num;
}
int main()
{
	test01();
	test02(100, 200);
	cout << "返回值為：" << test03() << endl;
	cout << "返回值為：" << test04(100) << endl;
	system("pause");
	return 0;
}

數(shù)據(jù)類型 函數(shù)名(參數(shù)列表)

#include<iostream>
using namespace std;

//函數(shù)的聲明
int maxtest(int a, int b);

int main()
{
	//int maxtest(int a, int b); 寫這里也可以
	int a = 10;
	int b = 20;
	cout << maxtest(a, b) << endl;
	system("pause");
	return 0;
}
//定義函數(shù)
int maxtest(int a, int b)
{
	return a > b ? a : b;
}

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

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

#include<iostream>
#include"swap.h"
using namespace std;

int main()
{
	int a = 10, b = 20;
	swap(a, b);
	system("pause");
	return 0;
}