//This program will take ten donations and count the average.
//If the user enters a number, then it will stop asking for numbers.
//Also, it will count the average of all numbers until the letter, if entered.

#include <iostream>
#include <cctype>

using namespace std;

const int ArSize = 10;

int main(void)
{

	//Variables:
	double donation[ArSize];
	double average = 0;
	int size = 0;
	int index;
	int wrong;
	
	//Loop for entering:
	for (index = 0; index < ArSize; index++)
	{
		cout << "Write number " << index + 1 << '\n';
		cin >> donation[index];
		if (isalpha(donation[index]))
		{
			cin.clear();
			donation[index] = 0;
			wrong = index;
			break;
		}
	}

	//Loop for counting:
	for (index = 0; index < ArSize; index++)
	{
		if (index == wrong)
			break; 
		average = average + donation[index];
		size = index + 1;
	}

	//End:
	average = average / size;
	cout << "The average is " << average;
	return 0;
}

if(!(cin >> donation[index])) {  // Oops, there's something at the beginning of the input stream  // which can't be interpreted as a double.  // First, make cin "recover" so that we can read more data  cin.clear();  // Skip past the garbage data, until a new line  cin.ignore(std::numeric_limits<INT_MAX>, '\n'); // <-- I think that's right...  // "Cancel the input" as you say  donation[index] = 0;  // In this case, the poster telling you to initialize the array  // is not on the right track; with this setup, something valid  // will get written to each array element.}

size = 0repeat 10 times:  try to assign input to donation[size]  if successful: size = size + 1  otherwise: recover cin and ignore the input  # there is no longer a need for a "wrong" variable# After every iteration of the loop, "size" points at the first# slot that hasn't been written to yet, so you won't overwrite# things or skip array slots. It's also equal to the number of# assigned slots, so after the loop, it tells you how many slots# are assigned. This is why 0-based indexing is a Good Thing :)sum = 0# So now, we need to loop size-many times, to grab all the# assigned values, and add them up:repeat with i from 0 to (size - 1):  sum = sum + donation# and now that we have the sum, and number of elements,# getting the average is easy:print (sum / size)