Alphabetical characters. Help.

[JulyZerg]

ok i am almost done with this program, but i am stuck, well sort of. i need help with compressing, i guess you can say, the program.
examples of the program i want to finish:
ex1: Julio.
Valid name

ex2: julio123
your name cannot contain: 1
your name cannot contain: 2
your name cannot contain: 3
Invalid name

and as of now i have done everything, but right now my program outputs everything like. J is a valid name, u is a valid name etc. and when it encounters a 1, invalid name, your name cannot contain: 1. but it will output the rest of the letters. i want it to not output the "valid name" for each of the alphabetical letters, but just output what is wrong with the name. i think i am just babbling at this point. the examples should tell you what must be done.
and this is my code so far.

#include <iostream>
#include <cstring>
using namespace std;

int main()
{
    char first_name[100];

    cout << "What's your first name?" << endl;
    cin >> first_name;

    for(int i = 0; i < first_name[i] != '\0'; i++)
    {
        if (first_name[i] >= 'A' && first_name[i] <= 'Z' || first_name[i] >= 'a' && first_name[i] <= 'z')
        {
            cout << "Valid name." << endl;

            if (first_name[i] <= '0' && first_name[i] >= '64' || first_name[i] <= '91' && first_name[i] >= '96' || first_name[i] <= '123' && first_name[i] >= '127')
            {
                cout << "invalid name." << endl;
            }

        }
        else
        {
            cout << "Your name cannot contain: " << first_name[i] << endl;
            cout << "Invalid name." << endl;

        }

    }
    //cout << "Valid name." << endl; <--Ignore.

}

[keskiverto]

http://www.cplusplus.com/reference/cctype/isalpha/

bool Valid = true
LOOP over the characters
  IF character is not ok
  THEN set Valid false and break

IF Valid is still true after the loop
THEN no character was bad