The format, commonly identified by the .doc file extension, served as the primary standard for digital word processing for nearly a decade. While superseded by the modern XML-based .docx format, it remains a critical legacy format for archiving and cross-version compatibility. Understanding the .doc Binary Format
Unlike modern text files, the format is a complex binary interchange file format . It uses a structured OLE 2.0 compound file system, essentially acting like a "file within a file" that contains various streams for text, formatting, and metadata. [MS-DOC]: Word (.doc) Binary File Format - Microsoft Learn microsoft office word 97 - 2003 document (.doc) download