What is the encoding of the file? Assuming byte-oriented: If UTF-8 then the character is 2 bytes. If ISO-8859-1 (also known as Latin-1) then the character is only 1 byte. Those are the two most likely byte-oriented encodings, though not the only ones.
No matter: You must know the file's encoding, and then know your language's string encoding. There are several ways to do this, but all require that you are aware of the encoding.
I have seen tools that cause confusion. For example, my Linux shell is UTF-8 encoded. But if I load an ISO-8859-1 encoded file and then save it, GNU Emacs reads it correctly and coverts it to UTF-8, changing the encoding out from under me and causing me to think my Latin-1 converter was broken.
A hex editor (bvi is one of many) is invaluable for helping track down these types of issues.