/* Program to process exam grades and illustrate passing an array to a function */
#include <iostream>
#include <fstream>
#include <cstdlib>          //needed to use exit() function
using namespace std;

const int SIZE = 50;

/* Function Prototypes */
void readdata(int [], int &);
int sumarray(int [], int);
double avgarray(int [], int);

int main()
{
    int num;
    int mark[SIZE];
    double avgmark;

    // call function to read the marks
    readdata(mark,num);

    // print the mark array
    cout << endl << endl << "The values of the array are:" << endl;
    for (int count = 0; count < num; count++)
        cout << "mark[" << count << "]=" << mark[count] << endl;

    // find and print the average mark
    avgmark = avgarray(mark,num);
    cout << endl << "The average is " << avgmark << endl;
//  system("pause");    //un-comment when using DevC++
    return 0;
}

/* Function sumarray()
 * Input:
 *  numbers - an array of integers
 *  n - the number of elements in the array
 * Process:
 *  finds the sum of the first n elements in the numbers array.
 * Output:
 *  returns the sum to the calling function.
 */
int sumarray(int numbers[], int n)
{
    int sum=0;

    for (int count = 0; count < n; count++)
        sum += numbers[count];
    return(sum);
}

/* Function avgarray()
 * Input:
 *  numbers - an array of integers
 *  n - the number of elements in the array
 * Process:
 *  calls sumarray to find the sum of the first n elements
 *  and then divides by n to find the average.
 * Output:
 *  returns the average to the calling function.
 */
double avgarray(int numbers[], int n)
{
    return ((double)sumarray(numbers,n)/n);
}

/* Function readdata()
 * Input:
 *  numbers - an array to be filled
 *  n - a reference to the number of elements in the array
 *  the parameters are uninitialized upon entry
 * Process:
 *		reads n and reads n values into the array
 * Output:
 *  the filled numbers array
 *  n - the number of elements in the array
 */
void readdata(int numbers[], int &n)
{
    //un-comment to redirect cin to a file
    //ifstream cin("c:\\bc\\CISC1110\\pgms\\chapter7\\myinput.txt");

    cout << "Enter the number of marks: ";
    cin >> n;

    if (n > 0 && n <= SIZE)
        cout << endl << "There are " << n << " marks" << endl << endl;
    else
    {
        cout << "Invalid number of marks" << endl;

//      system("pause");    //un-comment when using DevC++
        exit(1);
    }

    // enter the marks
    for (int count = 0; count < n; count++) {
        cout << "Enter a mark: ";
        cin >> numbers[count];
    }
    return;
}