Assignment due in 1 day (Not showing valid) ISBN errors also.

Hey guys i really need help ASAP..

Code:

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#include <iostream>
#include <limits>

void draw_menu()
{
    std::cout << "******************************************************************\n"
              << "* choose an entry from 1 to 3.  *\n"
              << "* [1] validate modulus 11 number  *\n"
              << "* [2] validate data  *\n"
              << "* [3] quit  *\n"
              << "******************************************************************\n";
}

int get_number() // read a valid number from stdin
{
    int number ;
    if( std::cin >> number ) return number ;

    // invalid input, inform the user, clear the input buffer and try again
    std::cout << "invalid number. please re-enter\n" ;
    std::cin.clear() ;
    std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
    return get_number() ;
}

int get_choice() // display the menu, return valid choice entered by the user
{
    draw_menu() ;

    const int choice = get_number() ;
    if( choice >= 1 && choice <= 3 ) return choice ; // valid choice

    return get_choice() ; // invalid choice, try again
}

bool valid_date( int dd, int mm, int yy )
{
    // *** TO DO: validate that dd/mm/yy forms a valid date
    //            if valid, return true

    return false ;
}

bool valid_modulo_11( int number )
{
    // *** TO DO: validate that number is a valid modulo 11 number
    //            if valid, return true

    return false ;
}

int main()
{
    bool quit = false ;

    do
    {
        const int choice = get_choice() ;

        switch(choice)
        {
            case 1:
            {
                std::cout << "enter modulo 11 number: " ;
                const int number = get_number() ;

                if( valid_modulo_11(number) ) std::cout << "yes, valid modulo 11 number\n" ;
                else std::cout << "that is not a valid modulo 11 number\n" ;

                break ;
            }

            case 2:
            {
                std::cout << "enter day: " ;
                const int dd = get_number() ;
                std::cout << "enter month: " ;
                const int mm = get_number() ;
                std::cout << "enter year: " ;
                const int yy = get_number() ;

                if( valid_date( dd, mm, yy ) ) std::cout << "valid date\n" ;
                else std::cout << "invalid date\n" ;

                break ;
            }

            case 3: quit = true ;
        }

    } while( !quit ) ;
}

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You don't have any code that would validate the number. Have you been given an algorithm do to it?

Please be a bit more specific about what's wrong.

Your code at present will always say that any number is not a valid modulo 11 number as the function always returns false! You need to provide the code for valid_modulo_11().