为什么我的while语句没有结束？

Question

I've created this program to calculate scores of peoples tests and count the number of grades. What i want to happen is that when the user enters "//" when the program asks "Enter student Name", the while statement should end, or that's what i assume should happen. What actually happens is that i type "//" then the program asks for the score, then the while statement ends. Why is this and what should i do to fix it?

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;

int main()
{
    string name, grade;
    int score;
    int count1 = 0;
    int acount = 0;
    int bcount = 0;
    int ccount = 0;
    int dcount = 0;
    int fcount = 0;
    while (name != "//") {
        cout << "Enter Student Name \n";
        cin >> name;
        cout << "Enter Student Score \n";
        cin >> score;
        count1 += 1;
        if (score >= 90) {
            grade = "A";
            acount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 80) {
            grade = "B";
            bcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 70) {
            grade = "C";
            ccount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 60) {
            grade = "D";
            dcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score <= 59) {
            grade = "F";
            fcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
    };
    cout << "Summary Report \n" << "Total Students Count: " << count1 << endl;
    cout << "A student count: " << acount << endl;
    cout << "B student count: " << bcount << endl;
    cout << "C student count: " << ccount << endl;
    cout << "D student count: " << dcount << endl;
    cout << "F student count: " << fcount << endl;
    return 0;
}

Answer 1

Most of the things have been already said in the comments:

Your problem is, that you expect the loop to check its condition continuously, which it does not.

while(name != "//") // here the condition is evaluated
{
    name = "//";    // here it is not 
     // the following code is executed, independent of the current name value
} // here the program jumps back to the loop condition, which is now false and it will not enter another time.

Like mentioned in the comments, a working alternative could be:

while(true)
{
    std::cin >> name;
    if(name == "//")
        break;
    else
        evaluateScore();
}

Answer 2

Try this:

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;

int main()
{
    string name, grade;
    int score;
    int count1 = 0;
    int acount = 0;
    int bcount = 0;
    int ccount = 0;
    int dcount = 0;
    int fcount = 0;
    while (true) {  // keep running the loop
        cout << "Enter Student Name \n";
        cin >> name;
        if(name == "//")  // if "//" found, break the loop
            break;
        cout << "Enter Student Score \n";
        cin >> score;
        count1 += 1;
        if (score >= 90) {
            grade = "A";
            acount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 80) {
            grade = "B";
            bcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 70) {
            grade = "C";
            ccount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score >= 60) {
            grade = "D";
            dcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
        else if (score <= 59) {
            grade = "F";
            fcount += 1;
            cout << name << " " << score << " " << grade << endl;
        }
    };
    cout << "Summary Report \n" << "Total Students Count: " << count1 << endl;
    cout << "A student count: " << acount << endl;
    cout << "B student count: " << bcount << endl;
    cout << "C student count: " << ccount << endl;
    cout << "D student count: " << dcount << endl;
    cout << "F student count: " << fcount << endl;
    return 0;
}