TXT is a file format that contains the text, organized in rows. Text files opposed binaries that contain data that is not intended for interpretation as a text (encoded sound or image). The text file can contain both formatted and unformatted text. Since the very simple text files, they are frequently used for storing data.
DOC is a file extension for word processing documents. It is associated mainly with Microsoft Word application. DOC files can also contain charts and tables, videos, images, sounds and diagrams. It supports almost all the Operating Systems.