one question on vector 's size

Hi~
 you guys
 look at my code below:
////////////////////////////////////////////////////////////////////////////
////////////
#include<string>
#include<vector>
#include<iostream>
#include<fstream>
using namespace std;

int main()
{
    vector<char> vch;
    cout<<vch.size()<<endl;
    ifstream fin("test.txt");
    while(!fin.eof())
    {
            char c;
                //cin also the same , if you add Ctrl+Z at the end of
your input
        fin>>c;
        vch.push_back(c);
        cout<<vch.size()<<endl;
    }
    for(size_t i=0;i!=vch.size();++i)
        cout<<vch[i]<<endl;
}
//use Dev C++ 4.9.9.2 beta edition
////////////////////////////////////////////////////////////////////////////
///////////////
At first ,I put in the int num from keyboard.
and after pressing the key-Enter,I put in Ctrl+Z as the signal of end.
but the output shows that the size of vch is 5 and each element is
's'.

Then I tried the ifstream.
for simple,the "test.txt" content: ssss
just 4 characters
and the result is the same.

What is wrong ?

Thanx!

p.s. My English is so ...bad ! :-P
    If you find some wrong in syntax,you might point out it.I will
appreciate you !

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