Solution of #1:

#include <iostream>
#include <fstream>
#include <ctime>
#include <string>
using namespace std;
int main()
{
	int n, i;
	ofstream outFile;
	string fileName;
	cout << "Enter a positive intger: ";
	cin >> n;
	cout << "Enter file's name: ";
	cin >> fileName;
	outFile.open(fileName.c_str());
	srand(time(0));
	for (i = 1; i <= n; i++)
	{
		outFile << rand() % 101 << endl;
	}
	outFile.close();
	return 0;
}


Solution of #2:

#include <iostream>
#include <fstream>
#include<string>
using namespace std;
int main()
{
	int n, i = 0, grade, count = 0, a[100];
	ifstream inFile;
	string fileName;
	cout << "Enter file's name: ";
	cin >> fileName;
	inFile.open(fileName.c_str());
	if (!inFile)
	{
		cout << Cant opne file:\n;
		return 1;
	}
	inFile >> grade;
	while(inFile && i < 100)
	{
		a[i] = grade;
		if (grade == 87)
			count++;
		i++;
		inFile >> grade;
	}
	inFile.close();
	n = i;
	for (i = 0; i < n; i++)
		cout << a[i] << \t;
	cout << endl;
	return 0;
}

Solution of #3:

#include <iostream>
#include <fstream>
#include<string>
using namespace std;
int main()
{
	int i, n, a[100], max, sum = 0;
	cout << "Enter the actual size of the array: ";
	cin >> n;
	if (n > 0)
	{
		for (i = 0; i < n; i++)
		{
			cout << "Enter an integral grade: ";
			cin >> a[i];
		}
		max = a[0];
		sum = a[0];
		for (i = 1; i < n; i++)
		{
			sum += a[i];
			if (a[i] > max)
				max = a[i];
		}
		cout << "\n\tThe average is: " << sum / float(n) << endl;
		cout << "\tThe maximum is: " << max << endl << endl;
	}
	else
		cout << "You have to eneter a positive integr.\n";
	return 0;
}