c13-16.cpp

这我们老师对是面向对象程序设计（清华大学出版社）一书制作的PPT

#include <fstream>
using namespace std;
struct student
{int num;
 char name[20];
 float score;
};
int main()
{int i;
 student stud[5]={1001,"Li",85,1002,"Fun",97.5,1004,"Wang",54,
                  1006,"Tan",76.5,1010,"ling",96};
 fstream iofile("stud.dat",ios::in|ios::out|ios::binary);
 if(!iofile)
  {cerr<<"open error!"<<endl;
   abort();
  }
 for(i=0;i<5;i++)
   iofile.write((char *)&stud[i],sizeof(stud[i]));
 student stud1[5];
 for(i=0;i<5;i=i+2)
   {iofile.seekg(i*sizeof(stud[i]),ios::beg);
    iofile.read((char *)&stud1[i/2],sizeof(stud1[i]));
    cout<<stud1[i/2].num<<" "<<stud1[i/2].name<<" "<<stud1[i/2].score<<endl;
   }
 cout<<endl;
 stud[2].num=1012;
 strcpy(stud[2].name,"Wu");
 stud[2].score=60;
 iofile.seekp(2*sizeof(stud[0]),ios::beg);
 iofile.write((char *)&stud[2],sizeof(stud[2]));
 iofile.seekg(0,ios::beg);
 for(i=0;i<5;i++)
   {iofile.read((char *)&stud[i],sizeof(stud[i]));
    cout<<stud[i].num<<" "<<stud[i].name<<" "<<stud[i].score<<endl;
   }
 iofile.close();
 return 0;
}