C、C++中的文本输入输出

#include <iostream>
#include <fstream>
#include <string>


using namespace std;


//输出空行
void OutPutAnEmptyLine()
{
    cout<<"\n";
}


//读取方式: 逐词读取, 词之间用空格区分
//read data from the file, Word By Word
//when used in this manner, we'll get space-delimited bits of text from the file
//but all of the whitespace that separated words (including newlines) was lost. 
void ReadDataFromFileWBW()
{
    ifstream fin("data.txt");  
    string s;  
    while( fin >> s ) 
    {    
        cout << "Read from file: " << s << endl;  
    }
}


//读取方式: 逐行读取, 将行读入字符数组, 行之间用回车换行区分
//If we were interested in preserving whitespace, 
//we could read the file in Line-By-Line using the I/O getline() function.
void ReadDataFromFileLBLIntoCharArray()
{
    ifstream fin("data.txt"); 
    const int LINE_LENGTH = 100; 
    char str[LINE_LENGTH];  
    while( fin.getline(str,LINE_LENGTH) )
    {    
        cout << "Read from file: " << str << endl;
    }
}


//读取方式: 逐行读取, 将行读入字符串, 行之间用回车换行区分
//If you want to avoid reading into character arrays, 
//you can use the C++ string getline() function to read lines into strings
void ReadDataFromFileLBLIntoString()
{
    ifstream fin("data.txt");  
    string s;  
    while( getline(fin,s) )
    {    
        cout << "Read from file: " << s << endl; 
    }
}


//带错误检测的读取方式
//Simply evaluating an I/O object in a boolean context will return false 
//if any errors have occurred
void ReadDataWithErrChecking()
{
    string filename = "dataFUNNY.txt";  
    ifstream fin( filename.c_str());  
    if( !fin ) 
    {   
        cout << "Error opening " << filename << " for input" << endl;   
        exit(-1);  
    }
}


int main()
{
    ReadDataFromFileWBW(); //逐词读入字符串 
    OutPutAnEmptyLine(); //输出空行


    ReadDataFromFileLBLIntoCharArray(); //逐词读入字符数组
    OutPutAnEmptyLine(); //输出空行


    ReadDataFromFileLBLIntoString(); //逐词读入字符串
    OutPutAnEmptyLine(); //输出空行


    ReadDataWithErrChecking(); //带检测的读取
    return 0;

}

//※计算两个数相加，用文件输入输出，这个是肯定正确的。
#include<cstdio> 
int main() 
{ 
      /*请务必于代码开头加入以下两行*/ 
      freopen("input.txt","r",stdin);             //关键代码，文件输入
      freopen("output.txt","w",stdout);       //关键代码，文件输出
      int a,b; 
      scanf("%d%d",&a,&b); 
      printf("%d\n",a+b); 
      return 0; 
  }