C++:概述

1.基本的输入输出,使用cin>>输入输入、使用cout<<输出

#include<iostream>
using namespace std;
int main()
{
  int a,b,d,min;
  cout<<"Enter two numbers:"<<endl;
  cin>>a>>b;
  cout<<"min = "<<(min=a>b? b:a);
  for(d=2;d<min;d++)
    if(((a%d)==0) && ((b%d)==0)) break;
  if (d==min)
   {
    cout<<"no common denominators"<<endl;
    return 0;
   } 
  cout<<"the lowest common denominator is"<<d<<endl; 
  return 0;
} 

Enter two numbers:
1
2
min = 1
the lowest common denominator is2
Program ended with exit code: 0

2.使用引用,引用用地址符号&表示,引用就是给变量或者常量起的另一个别名,操作的还是同一个数据

//引用当做返回值

/*
需求：使用引用返回函数值 
*/
#include<iostream>
using namespace std;
int &f(int &i)    //定义函数返回一个整数类型的引用，等价于返回数值i 
{
 i+=10;
 return i; 
} 
int main()
{
  int k=0;
  int &m=f(k); //k=i=10
  cout<<k<<endl;
  m=20;
  cout<<k<<endl;
  return 0;
} 

10
20
Program ended with exit code: 0

//引用当做参数

/*
 需求:引用作为函数参数 
*/
#include<iostream>
using namespace std;
void f(int &m,int n)
{
 int temp;
 temp = m;
 m = n;
 n =temp;
}
int main()
{
 int a = 5,b = 10;
 cout<<"a = "<<a<<" "<<"b = "<<b<<endl; 
 f(a,b);
 cout<<"a = "<<a<<" "<<"b = "<<b<<endl;
 return 0;
} 

a = 5 b = 10
a = 10 b = 10
Program ended with exit code: 0

 3.使用作用域运算符::,作用变量或常量或函数的有效区域

/*
 需求：作用域运算符:: 
*/
#include<iostream>
using namespace std;
int i=15;
int main ()
{
 int i;
 i = 100;
 ::i = i+1;
 cout<<i<<endl;
 cout<<::i<<endl;
 return 0; 
}

100
101
Program ended with exit code: 0

4.结构体的简单使用,它有自己的属性成员和方法成员，需要创建结构体成员变量才能调用自己的属性和方法

//#include<iostream>
//#include<cmath>
//using namespace std;
#include<iostream.h>
#include<math.h>
struct Complex                 //声明一个名为Complex的结构体 
{
 double real;                  //数据成员，复数的实部 
 double imag;                  //数据成员，复数的虚部 
 void init(double r,double i)  //成员函数init，给real和imag赋给初值 
 {
  real = r;
  imag = i;
 }
 double abscomplex()           //成员函数，求复数的绝对值 
 {
  double t;
  t = real*real+imag*imag;
  return sqrt(t);
 }
};
 int main()
 {
  Complex A;              //定义结构体Complex的成员变量A
  A.init(1.1,2.2);        //调用成员函数init，给real和imag赋给初值 
  cout<<"复数的绝对值是:"<<A.abscomplex()<<endl; //调用成员函数abscomplex 
  return 0; 
 }

复数的绝对值是:2.45967
Program ended with exit code: 0