贺老师的教学链接  本课讲解

示例：将数据写入ASCII文件

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main( )
{int a[10];ofstream outfile("f1.dat",ios::out);//定义文件流对象，打开磁盘文件"f1.dat"if(!outfile)                        //如果打开失败，outfile返回0值{cerr<<"open error!"<<endl;exit(1);}cout<<"enter 10 integer numbers:"<<endl;for(int i=0; i<10; i++) //向磁盘文件"f1.dat"输出数据{cin>>a[i];outfile<<a[i]<<" ";}cout<<"The numbers have been writen to file. "<<endl;outfile.close();       //关闭磁盘文件"f1.dat"return 0;
}

示例：从ASCII文件读入数据

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main( )
{int a[10],max,i,order;ifstream infile("f1.dat",ios::in);//定义输入文件流对象，以输入方式打开磁盘文件f1.datif(!infile){cerr<<"open error!"<<endl;exit(1);}for(i=0; i<10; i++){infile>>a[i];  //从磁盘文件读入10个整数，顺序存放在a数组中cout<<a[i]<<" ";}          //在显示器上顺序显示10个数cout<<endl;max=a[0];order=0;for(i=1; i<10; i++)if(a[i]>max){max=a[i];                //将当前最大值放在max中order=i;                 //将当前最大值的元素序号放在order中}cout<<"max="<<max<<endl<<"order="<<order<<endl;infile.close();return 0;
}

示例：读写ASCII文件

#include<iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void save_to_file( );
void get_from_file();
int main( )
{save_to_file( );get_from_file( );return 0;
}
void save_to_file( )
{ofstream outfile("f2.dat");if(!outfile){cerr<<"open f2.dat error!"<<endl;exit(1);}char c[80];cin.getline(c,80);for(int i=0; c[i]!=0; i++) if(c[i]>='a' && c[i]<='z')outfile.put(c[i]);    outfile.close();
}
void get_from_file()
{char ch;ifstream infile("f2.dat",ios::in);if(!infile) {cerr<<"open f2.dat error!"<<endl;exit(1);}ofstream outfile("f3.dat");if(!outfile){cerr<<"open f3.dat error!"<<endl;exit(1);}while(infile.get(ch))outfile.put(ch-32);     infile.close( );     outfile.close();
}

示例：在显示器上输出文件

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
void display_file(char *filename);int main( )
{display_file("f3.dat");return 0;
}
void display_file(char *filename)
{ifstream infile(filename,ios::in);if(!infile){cerr<<"open error!"<<endl;exit(1);}char ch;while(infile.get(ch))cout.put(ch);cout<<endl;infile.close();
}