求解释C++的read函数？？

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
const int num=10;
struct people 
{
 char name[num];
 int age;
 float pay;
};
int main()
{
 people pp={"陈涛",25,945.34f};
 ofstream fout("people.txt",ios::out|ios::binary);
 fout.write((char*)&pp,sizeof pp);
 fout.close();
 people pp1={"李力持",45,1065.58f};
 fout.open("people.txt",ios::in|ios::out|ios::binary);
 fout.seekp(sizeof pp,ios::beg);
 fout.write((char*)&pp1,sizeof pp1);
 fout.close();
  people pp2={"刘伟",40,1060.58f};
 fout.open("people.txt",ios::in|ios::out|ios::binary);
int a=(sizeof pp)+(sizeof pp1);
 fout.seekp(a,ios::beg);
 fout.write((char*)&pp2,sizeof pp2);
 fout.close();

  fstream InOut; 
InOut.open("people.txt",ios::in|ios::out|ios::binary);
int count=0;
  fout.seekp(a,ios::beg);
  while (InOut.read((char*)&pp,sizeof pp))
{
cout<<count++<<":"<<setw(num)<<pp.name<<":"
<<setprecision(0)<<setw(12)<<pp.age
<<setprecision(2)<<setw(16)<<pp.pay<<endl;
}
InOut.close();
cout<<"完成\n";
 return 0;
}
其中的InOut调用read函数为什么可以把PP,PP1，PP2读出来，

read()和cin相似啊，只不过是从文件中读取。第二个参数表示一次读取的缓冲区大小

msdn看一下方法