// Torrez, Elaine                           CS1A                     Chapter 5 P. 294, #1
 
/******************************************************************************************
 * 
 * Sum of Numbers
 * 
 * --------------------------------------------------------------------------------
 * This program asks the user for a positive integer value. The program uses a loop 
 * to calculate the sum of all integers from 1 up to the number entered.
 * --------------------------------------------------------------------------------
 * 
 * INPUT
 *      number       : A positive integer entered by the user
 * 
 * OUTPUT
 *      sum          : The total sum of all integers from 1 to the entered number
 * 
 *******************************************************************************************/
 
#include <iostream>
using namespace std;
 
int main ()
{
    int number;    // INPUT - A positive integer entered by the user
    int sum = 0;   // OUTPUT - Sum of all numbers from 1 to 'number'
 
    // Prompt user for a positive integer
    cout << "Enter a positive integer: ";
    cin >> number;
 
    // Input Validation: must be positive
    while (number <= 0)
    {
        cout << "Error! Please enter a positive integer: ";
        cin >> number;
    }
 
    // Loop to calculate the sum
    for (int i = 1; i <= number; i++)
    {
        sum += i;
    }
 
    // OUTPUT: Display the result
    cout << "\nThe sum of numbers from 1 to " << number << " is " << sum << endl;
 
    return 0;
}
 

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