Help with the << input in parentheis

[Blackhart98]

Im having a very hard time understanding this (cin >> x). Im just getting into c++ and im reading accelerated c++. In the book its a program on making a student grade chart this is the code.

while (cin >> x) 

This is the code im having a extremely hard time understanding. So is x going into the input of cin?? if so what is cin this is the full code..

#include <iomanip>
#include <ios>
#include <iostream>
#include <string>
using namespace std;

int main()
{
    //ask for and read the student's name
    cout << "Please enter your name ";
    string name;
    cin >> name;
    cout << "Hello " << name << "!" << endl;
    //ask for and read the midterm and final grades
    cout << "Please enter your midterm and final exam grades: ";
    double midterm , final;
    cin >> midterm >> final;
    //ask for homework grades
    cout << "enter all your homework grades, "
    "followed by end-of-file: ";
    // the number and sum of grades read so far
    int count = 0;
    double sum = 0;
    // a variable into which to read
    double x;
    //invariant
    //we have to read count grades so far , and
    // sum is the sum of the first count grades
    while (cin >> x) {

    ++count;
    sum+= x;
    }
    /// write the result
    streamsize prec = cout.precision();
    cout << "Your final grade is" << setprecision(3)
    << 0.2 *midterm + 0.4 * final + 0.4 * sum / count
    << setprecision (prec) << endl;
    return 0;
}

It runs perfectly because I copied it from the book I just don't understand what the hell does that mean. I just don't get it im assuming that cin is the last output ,but what >> does. Is it like cout << or what it is really confusing me right now please respond.

[jlb]

The line while(cin >> x) will try to extract a value into the variable until an error occurs. This error is triggered by either eof() or trying to insert something that the variable can't accommodate. For example trying to enter a character for a numeric entry.

The C++ streams can return a Boolean type of value that indicates success or failure.