Simple text-to-binary converter written in C++

I am learning C++ on my own and was hoping for some feedback on this simple text-to-binary converter. The program runs and I haven't encountered any errors with it yet. Any input is welcome.

#include 
#include 
#include 

using namespace std;

int main()
{
char letter = ' ', playAgain = 'y';
string word = " ";

cout  binary(letter);

        cout > playAgain;

    if (playAgain != 'y'){
        cout << "\n\nExiting program.";
        playAgain = 'n';
        }
        cin.ignore();
}

return 0;
}

As already mentioned, your code is looking okay. Here are my additions:

-
It's best not to use using namespace std.

-
Variables should be declared/initialized on their own line:

char letter = ' ';
char playAgain = 'y';

-
You don't need a newline between every line of code. This will just make your program appear longer and harder to read. Just separate lines into groups based on purpose.

-
Variable declarations/initializations should be placed as close in scope as possible to where they will be first used:

std::cout << "Please enter a character, word, or phrase: ";
std::string word; // declaration is first used here
getline(std::cin, word, '\n');

-
Your main loop could use for (;;). This is essentially an infinite loop, but it should do a break at the end if the user inputs a value other than 'Y':

for (;;)
{
    // do stuff

    std::cout > playAgain;
    std::cin.ignore();

    if (playAgain != 'Y')
    {
        break;
    }

    // playAgain is 'y', so do stuff again
}

-
Prefer to use std::string::size_type for the inner for-loop as it's the type returned from std::string::size().

Or if you have C++11, use a range-based for loop instead:

for (auto iter& : word)
{
    letter = iter;

    // ...
}

StackExchange Code Review Q#2661, answer score: 11