need some help Bool and loops

Ok I am making a program that the user has to enter up to 8 digits to make a binary number so it they have to be 0 or 1. I need help in 2 spots how do I limit cin to only allow user to input up to 8 characters. and cant get my loops to work right. Please help me =)

Code:

// InvalidBinDr.cpp

#include<iostream>
#include<string>
#include<cctype>
using namespace std;

// FILL IN InvalidBin PROTOTYPE:


int main()
{
// Variables local to main
bool inValid=true; // True if an invalid binary # is entered
string strVal; // The user entered string



cout << "Please enter a string." << endl;
cin >> strVal;

if(inValid)
cout << strVal << " is not a binary number." << endl;
else
cout << strVal << " is a binary number." << endl;
while(strVal=="0" || strVal=="1")


return 0;
}

// FUNCTION InvalidBin RETURNS TRUE IF THE STRING ENTERED BY THE
// USER DOES NOT REPRESENT A VALID 8-BIT BINARY NUMBER OTHERWISE
// IT RETURNS FALSE, (i.e. the string has 8 bits that are 1's or
// 0's only).

ok have gotten this far now. now I cant get my loop to work correct. anyone help I bad at loops.

Code:

// InvalidBinDr.cpp 

#include<iostream>
#include<string>
#include<cctype>
using namespace std;

// FILL IN InvalidBin PROTOTYPE: 

 
int main()
{
	// Variables local to main
	bool inValid=true;	// True if an invalid binary # is entered
	char strVal;	// The user entered string



string input;
while (true) {
    cout << "Enter a binary number (8 digits or less): ";
    getline(cin, input);
    if (input.size() <= 8) break;
    cerr << "You entered more than 8 digits.  Please re-enter your number." << endl;
}
cin >> strVal;


	if(inValid)
		cout << strVal << " is not a binary number." << endl;
	else
		cout << strVal << " is a binary number." << endl;



	return 0;
}

// FUNCTION InvalidBin RETURNS TRUE IF THE STRING ENTERED BY THE
// USER DOES NOT REPRESENT A VALID 8-BIT BINARY NUMBER OTHERWISE
// IT RETURNS FALSE, (i.e. the string has 8 bits that are 1's or 
// 0's only).

ok I corrected a few mistakes. But still cant get my loop to work right..

Code:

// InvalidBinDr.cpp 

#include<iostream>
#include<string>
#include<cctype>
using namespace std;

// FILL IN InvalidBin PROTOTYPE: 

 
int main()
{
	// Variables local to main
	bool inValid=true;	// True if an invalid binary # is entered
	string input;// The user entered string

while (true) {
    cout << "Enter a binary number (8 digits or less): ";
    getline(cin, input);
    if (input.size() <= 8) break;
    cerr << "You entered more than 8 digits.  Please re-enter your number." << endl;
}



	if(inValid)
		cout << input << " is not a binary number." << endl;
	else
		cout << input << " is a binary number." << endl;



	return 0;
}

// FUNCTION InvalidBin RETURNS TRUE IF THE STRING ENTERED BY THE
// USER DOES NOT REPRESENT A VALID 8-BIT BINARY NUMBER OTHERWISE
// IT RETURNS FALSE, (i.e. the string has 8 bits that are 1's or 
// 0's only).

Help anyone?

I don't see any loop that actually tries to determine if the input is a binary number. Once you have obtained input that satisfies you, you'll have to loop to inspect each character of the string in turn and set inValid to false if the current character is not '0' or '1'.