打印出错误的值

Question

I'm trying to write a program that takes the grades and prints out the following:

ID:123 NAME:John GRADE:78

but instead I'm getting:

ID:-842150451 NAME: GRADE: 78

Can you guys help me and give me some extra tips to make my code cleaner since I'm fairly new to C++.

Student.h

#ifndef STUDENT_H
#define STUDENT_H
#include <iostream>
#include <string>
using namespace std;

class Student {
public:
    Student(int num, string text);
    int getID();
    void setExamGrade(int a, int b);
    int getOverallGrade();
    void display();
    string getName();
    string name;
    int id;
    int exams[3];
    int sum;
    int average;
};

#endif

Student.cpp

#ifndef STUDENT_CPP
#define STUDENT_CPP
#include "Student.h"
#include <iostream>
#include <string>
using namespace std;

Student::Student(int num, string text)
{
    num = id;
    text = name;

    exams[0, 1, 2] = 0;
}

int Student::getID() {
    return id;
}

string Student::getName() {
    return name;
}

void Student::setExamGrade(int a, int b) {
    exams[a] = b;
}

int Student::getOverallGrade() {
    sum = exams[0] + exams[1] + exams[2];
    average = sum / 3;
    return average;
}

void Student::display() {
    cout << "ID: " << getID();
    cout << " NAME: " << getName();
    cout << " GRADE: " << getOverallGrade() << endl;
}
#endif

gradebook.cpp

#ifndef GRADEBOOK_CPP
#define GRADEBOOK_CPP
#include "Student.h"
#include <iostream>
using namespace std;

int main() {

    Student *s = new Student(123, "John");
    s->setExamGrade(0, 80);
    s->setExamGrade(1, 60);
    s->setExamGrade(2, 95);
    s->display();
    delete s;

    return 0;
}

#endif

Answer 1

You never assign to id in the constructor, hence it's uninitialized and you will have undefined behavior when you print it.

Change

num = id;

to

id = num;

Same with the name .

---

Also, the statement

exams[0, 1, 2] = 0;

doesn't do what you expect it to do, it only initializes exams[2] to sero, and leaves the rest uninitialized. The expression 0, 1, 2 uses the comma operator .

Either assign to all members of the array separately, or use a constructor member initializer list (which I recommend for all the initialization).