Display menu, Calculate sum of odd numbers, Calculate pay, Draw triangle

/*---------------------------------------------------------------------------------------------------------------------
            Author : =-=[ccoder]=-=-
            Compiler : Microsoft Visual Studio 2008
            Purpose : Display menu, Calculate sum of odd numbers, Calculate pay, Draw triangle
            Limitations : No validation provided
----------------------------------------------------------------------------------------------------------------------*/
#include
#include
#include
using namespace std;

int main()
{
    char choice;
    char display_menu();
    void pay_caculation();
    void triangle_pattern();
    void scaffold();
    int odd_num_sum_cal();
   

    do
    {
        choice = toupper(display_menu());        // call function to display menu
        switch (choice)
        {
        case 'A':                                // select procedure to follow
            scaffold();
            break;
        case 'B':
            pay_caculation();
            break;
        case 'C':
            triangle_pattern();
            cout << endl << "C selected" << endl;
            break;
        case 'X':
            break;
        default:
            cout << endl << "Invalid choice -- try again" << endl;
        }
    }while (choice != 'X');                        // continue until exit selected
    return 0;
}

char display_menu()
{
    char choice;
                                        // display menu
    cout << endl << endl << "    MAIN MENU" << endl << endl;
    cout << "A. Sum of odd numbers " << endl;
    cout << "B. Calculate pay " << endl;
    cout << "C. Display Triangle Patterns " << endl;
    cout << "X. Exit " << endl << endl;
    cout << "Enter your choice : ";
    cin >> choice;
    return choice;
}

void scaffold()
{
    char answer = 'y';
    int number = 0;
    int sum_of_odd = 0;
    int odd_num_sum_cal(int number,int sum_of_odd);

    do
    {
        int sum_of_odd = 0;
        cout << "Please enter a number :";
        cin >> number;
        sum_of_odd = odd_num_sum_cal(number,sum_of_odd);
        cout << "\n" << "The sum of the odd numbers is : " << sum_of_odd;
        cout << "\n" << "Do you want to enter another number (Y/N) ?";
        cin >> answer;
    }while (toupper(answer)== 'Y');
}

int odd_num_sum_cal(int number,int sum_of_odd)
{
    for (int x=1; x <= number ; x++)
    {
        if (x % 2 == 1)
        {
            sum_of_odd = sum_of_odd + x;
        }
    }
    return sum_of_odd;
}

void pay_caculation()
{
    int number_days = 0;
    const int MAX = 20;
    double day_salary = 0.01;
    double total_pay = 0.01;
    int x = 1;
   
    cout << "Enter number of days: ";
    cin >> number_days;
   
    if (number_days <= MAX && number_days > 0)
    {
        cout << "DAY" << setw(19) << "PAY" << setw(25) << "TOTAL PAY" << endl;
        do
        {   
            cout << setprecision(2) << fixed;
            cout << setw(3)<< x << setw(19) << day_salary << setw(25) << total_pay << endl;
            day_salary = day_salary * 2;
            total_pay = total_pay + day_salary;
            x++;
        }while(x <= number_days && x <= MAX);
        cout << endl << "Number of days worked: " << number_days << endl;
    }
    else
    {
        cout << "Enter a number of worked days from 1 to 20 days max !" << endl;
    }
    system("pause");
}

void triangle_pattern()
{   
    char letter;
    char input_letter;

    cout << "Enter a letter: ";
    cin >> input_letter;
    input_letter = toupper(input_letter);

    for (int row = 0; row <= (input_letter - 'A'); row++)               
    {                                               
        letter = input_letter;
        for (int col = 0; col <= row; col++)                   
        {   
            cout << letter;
            letter = letter-1;   
        }   
        cout << endl;
    }
    system("pause");
}