print each character in string and some useful functions

This is example source code for how to print and access each character in string.
And using this function, I made some useful functions.
Thank you.


...

void printAndCountAllCh(string str)
{
    int count = 0;
    for (std::string::iterator it = str.begin(); it != str.end(); ++it) {
        std::cout << count << ": " << *it << endl;
        count++;
    }
}

string changeAtoB(string str, char A, char B)
{
    int count = 0;
    for (std::string::iterator it = str.begin(); it != str.end(); ++it) {
        if (string(1, *it) == string(1, A))
        {
            *it = B;
        }
    }

    return str;
}

string deleteA(string str, char A)
{
    string rstr;
    int count = 0;
    for (std::string::iterator it = str.begin(); it != str.end(); ++it) {
        if (string(1, *it) != string(1, A))
        {
            rstr.push_back(*it);
        }
    }

    return rstr;
}


int countNotCH(string str, char CH)
{
    int count = 0;
    for (std::string::iterator it = str.begin(); it != str.end(); ++it) {
        if (string(1, *it) != string(1, CH))
            count++;
    }
    return count;
}

int main()
{

    string str = "A_B CD_EF GH_I";
    int count;

    printAndCountAllCh(str); //print each char and count
    std::cout << endl;

    string abc = changeAtoB(str, ' ', '_'); //A_B CD_EF GH_I -> A_B_CD_EF_GH_I
    std::cout << abc << endl << endl;

    string bbb = deleteA(str, ' '); //A_B CD_EF GH_I -> A_BCD_EFGH_I
    std::cout << bbb << endl << endl;

    count = countNotCH(str, '_'); //A_B CD_EF GH_I -> 11
    std::cout << count << endl << endl;

    return 0;
}

...