C++ :: Using Isalpha With String Converted To Char Array

I am new to C++ and I have a two player word guessing game working well. However, I would like to be able to validate whether the word entered by player 1 is a completely alphabetic word using isalpha.

The error I am getting right now is as follows:

"error: array must be initialized with a brace-enclosed initializer
char str[100]=hiddenwordtwo;"

/* isalpha portion of code */
#include <stdio.h>
#include <ctype.h>
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <string>
#include <cstring>
using namespace std;

int main () {
char hiddenwordtwo[100];

[Code] .....