Grading Program and Boolean Variable Confusion!

[sadelbrid]

Okay Im a newbie and Im working on a program that allows the user to enter a grade (0-100) and then the console returns to the user the grade and the letter of the grade. This is what i have and so far I have only programmed grades 70 and up. Here's my problem: if the grade is 90 or above, the console displays "A".. which is fine. But when I enter a grade that is less than 90 and above 80, the console displays "AB".. then when I enter a grade above 70 and less than 80 the console displays "ABC".. this program is supposed to return grades, not teach me my ABCs. Please help and let me know if I am approaching this program completely wrong. Here's what I got:

#include <iostream>

using namespace std;

int main()
{
    bool P, A, B, C, D, F;
    P = false;
    A = false;
    B = false;
    C = false;

    int grade;
    cout << "Enter Grade:\n";
    cin >> grade;
    if (grade == 100)
    {
        P = true;
        if (P = true)
        {
            cout << "Perfect Score!";
        }
    }
    if (grade >= 90, grade < 100)
    {
        A = true;
        if (A = true)
        {
            cout << "A";
        }
    }
    if (grade >= 80, grade < 90)
    {
        B = true;
        if (B = true)
        {
            cout << "B";
        }
    }
    if (grade >= 70, grade < 80)
    {
        C = true;
        if (C = true)
        {
            cout << "C";
        }
    }

    return 0;
}

[Stewbond]

Replace
if (grade >= 90, grade < 100)
with
if (grade >= 90 && grade < 100)

The comma gets you to do two seperate operations. It doesn't replace the AND operator.

Note:
if (B = true) is probably not doing what you think it is doing. it is setting B equal to true (not comparing) and then returning that value (which is true).
Note 2:
Why would you set B = true; then if (B == true)? It seems unnessesary since the only times that you'll enter the for loop is if the line in front of it is called which always happens.

[vlad from moscow]

Also you can simplify your code for example

    if (grade >= 90, grade < 100)
    {
        A = true;
        if (A = true)
        {
            cout << "A";
        }
    }

the following way


if ( A = ( grade >= 90 && grade < 100 ) ) cout << "A";