Error Detection Based on Check Digit Schemes

// checksum6.cpp
//
#include "stdafx.h"

#include <iostream>
#include <string>
#include <assert.h>

#include "convert.h"

int main(int argc, char* argv[])
{
    // _tstring number = _T("0823");               // c = 5
    _tstring number = _T("276616973212561");    // c = 5

    _tcout << _T("number: ") << number << endl;

    unsigned int c = 10;

    for( _tstring::iterator it  = number.begin();
                            it != number.end(); it++ )
    {
        // Consume non digits
        while( it != number.end() && false == isdigit( *it ) ) { it++; }
        if(    it == number.end() ) { break; }

        c += CharToNumber( *it );

        if( c > 10 ) { c -= 10; }

        c *= 2;

        if( c >= 11 ) { c -= 11; }
    }

    c = 11 - c;

    if( 10 == c ) { c = 0; }

    _tcout << _T("check digit is: ") << c << endl;

    return 0;
}