ISO Error...

[compman9902]

I'm sorry for wasting your time with this question, but I just can't figure it out.
Every time I run my program in the DEV-C++ 4.9.9.2 compiler, it gives me this error:
ISO C++ forbids comparison between pointer and integer
Here is my code:

// ...
length = original.length();
cout << length;
position = 1;
while (position != length + 1)
{
   original[position] = letter;
   if (letter == "a")
   {
      std:stringstream out;
      out << a;
      string originalTwo(out.str());
      encryptedString += originalTwo;
   }
   position = position + 1;
}
// ...

Thank you for your time and help.

[Roonie]

. . . it would be useful to see how you declare the variables you are using.

. . . just a little more context please.

[compman9902]

. . . it would be useful to see how you declare the variables you are using.

. . . just a little more context please.

Thank You For Everything, But the Issue Has Been Resolved.