例: 输入个数不确定的成绩
#include <iostream>
using namespace std;
int main( )
{
float grade;
cout<<"enter grade:";
while(cin>>grade)//能从cin流读取数据
{
if(grade>=85)
cout<<grade<<" GOOD!"<<endl;
if(grade<60)
cout<<grade<<" fail!"<<endl;
cout<<"enter grade:";
}
cout<<"The end."<<endl;
return 0;
}
用于字符输入的流成员函数——get函数
（1）不带参数的get函数
#include <iostream>
using namespace std;
int main( )
{
int c;
cout<<"enter a sentence:"<<endl;
while((c=cin.get())!=EOF)
cout.put(c);
return 0;
}
(2) 有一个参数的get函数
#include <iostream>
using namespace std;
int main( )
{
char c;
cout<<"enter a sentence:"<<endl;
while(cin.get(c)) //读取一个字符赋给字符变量c，如果读取成功，cin.get(c)为真
cout.put(c);
cout<<"end"<<endl;
return 0;
}
(3) 有3个参数的get函数
#include <iostream>
using namespace std;
int main( )
{
char ch[20];
cout<<"enter a sentence:"<<endl;
cin.get(ch,10,'/');//指定‘/’符号为终止字符
cout<<ch<<endl;
return 0;
}
用于输入一行字符的流成员函数——getline函数
#include <iostream>
using namespace std;
int main( )
{
char ch[20];
cout<<"enter a sentence:"<<endl;
cin>>ch;
cout<<"The string read with cin is:"<<ch<<endl;
cin.getline(ch,20,'/');//读19个字符或遇'/'结束
cout<<"The second part is:"<<ch<<endl;
cin.getline(ch,20); //读19个字符或遇'/n'结束
cout<<"The third part is:"<<ch<<endl;
return 0;
}
判断输入(文件)是否结束——eof函数
#include <iostream>
using namespace std;
int main( )
{
char c;
while(!cin.eof( )) //eof( )为假表示未遇到文件结束符
if((c=cin.get( ))!=' ') //检查读入的字符是否为空格字符
cout.put(c);
return 0;
}
输入流其他函数——
#include <iostream>
using namespace std;
int main( )
{
char c[20];
int ch;
cout<<"please enter a sentence:"<<endl;
cin.getline(c,15,'/');
cout<<"The first part is:"<<c<<endl;
ch=cin.peek( ); //取当前字符
cout<<"next character: "<<char(ch)<<endl;
cin.putback(c[0]); //插入c[0]
cin.getline(c,15,'/');
cout<<"The second part is:"<<c<<endl;
return 0;
}
