Files with the DOC extension and those with the DOCX file extension are products of Microsoft Word. A file extension is the second part of a computer file name, coming after the dot (“.”). The intention of these file extensions is to give a quick idea of the format of the contents of files and the applications that open them.
DOC File Extension
DOC is an abbreviation for “document.” Earlier versions of Microsoft Word used the file extension to store user files created in the application. The file was stored in a binary format. The DOC file extension is not only used by Microsoft Word. It is also used by DisplayWrite 4, Interleaf, Palm Pilot, Samna Word and Adobe FrameMaker all of which employ the file extension to denote document files.
DOCX File Extension
Word is included in Microsoft Office. With the release of Office 2007, Microsoft changed the output format of all the suite's component programs. Instead of storing files in a binary format, Word now uses an Open XML format. The DOCX file extension was created to distinguish files with the new format from the old DOC binary format. The additional X signifies XML. Open XML is a version of the Extensible Markup Language. This is a plain text format with layout and text formatting instructions written in tags, which are signified by angle brackets. The XML file is compressed to form the DOCX file type.
Microsoft promotes the Open XML format for all of its programs. It sees the format as a neutral method for passing data between incompatible applications. It particularly intends its Office suite components to be able to exchange data with Open XML formats. The binary format of DOC files could only be opened by Word, or other applications with a Word adapter. Versions of Word since Office 2007 are still able to open the old DOC format files.
Apart from the format in which the files are stored, there is another major difference between DOC and DOCX files. A DOC file is capable of storing macros, a DOCX file cannot. A macro is a recorded sequence of commands that automate the population of template fields. Microsoft introduced a different file extension to signify macro-enabled files. This is the DOCM file extension. DOCM files are also stored in a compressed XML format.