MS Word Doc format is a family of formats used by older versions of MS Word (they now use DOCX as a default as of Office 2007).
Wikipedia says the following four types exist
- Word for DOS
- Word 1 & Word 2 for MS Windows, and Word 4 & 5 for Mac
- Word 6 & Word 95 for MS Windows, and Word 6 for Mac
- Word 97, 2000, 2002, 2003, 2007 & 2010 for MS Windows, and Word 98, 2001, X, & 2004 for Mac
What's up, DOC?
But just because the file you stumbled onto has a DOC extension doesn't mean it is necessarily actually a MS Word file, though if it's not that old it probably is. Older files, like from the 1980s or 1990s, might be something else entirely. Several other word processors in that era used .DOC file extensions, even though their format was nothing like MS Word's. Also, it was fairly common for people to save plain text files with that extension when they were DOCumenting something, like the instructions for a program that was packed up in an ARC or ZIP file for download on a bulletin board system (BBS). But you might still try opening them with Word (as will normally happen in Windows if you have Word installed and double-click on a DOC file), since it will open plain-text files all right (even ancient ones).