Reads a file called grades.txt with 20 grades, one on each line, and outputs the average of all the numbers.

calcGrades.cpp

#include <iostream>
#include <fstream>
using namespace std;

const int STUDENTS = 20;

double findAvg(int[]);

int main() {
    int grades[STUDENTS] ;
    
    ifstream in;
    in.open("grades.txt");
    int currLine;
    int cnt = 0;
    while (in >> currLine) {
        if (cnt>STUDENTS) {
            cout << "Error: excess number of grades.";
            break;
        }
        grades[cnt] = int(currLine);
        cnt++;
    }
    in.close();
    
    cout << findAvg(grades) << endl;
}

double findAvg(int grades[]) {
    int sum = 0;
    double avg = 0;
    for (int i = 0; i < STUDENTS; i++) {
        sum+=grades[i];
    }
    avg = double(sum) / double(STUDENTS);
    return avg;
}