a04sol.cpp

#include <iostream>
using namespace std;
int main()
{
    int month, day;
    int maxdays;
    cout << "Enter month: ";
    cin >> month;
    if(month < 1 || month > 12)
    {
        cout << "ERROR: Invalid month\n";
        return 0;
    }
    switch(month)
    {
        case 2: maxdays = 29; break;
        case 4: case 6: case 9: case 11:
            maxdays = 30; break;
        default:
            maxdays = 31;
    }
    cout << "Enter day: ";
    cin >> day;
    if(day < 1 || day > maxdays)
    {
        cout << "ERROR: Invalid day\n";
    }
    else {
        cout << day;
        switch(day)
        {
            case 1: 
            case 21: case 31:
                cout << "st";
                break;
            case 2: case 22:
                cout << "nd";
                break;
            case 3: case 23:
                cout << "rd";   
                break;
            default: cout << "th";
        }
    }
    return 0;
}

loops.cpp

#include <iostream>
using namespace std;
int main()
{
    int i, j, n;
    cout << "How many stars? ";
    cin >> n;
    // Print N stars across
    // Print N rows
    i = 1; // outer loop: each row
    while(i <= n)
    {
        j = 1; // inner loop: each column
        while(j <= n)
        {
            if(i == j || i+j == n+1) { cout << "*"; }
            else { cout << " "; }
            cout << i << "," << j << "   ";
            j = j + 1;
        }
        cout << "\n";
        i = i + 1;
    }

    return 0;
}