Microsoft Office/Things to Know When Saving

There are a menagerie of ways you can save a file in Microsoft Office, each with their own features and limitations. However, on a default windows installation, you might not be able to necessarily see the difference. This necessitates the enabling of file extensions, which represent the different types of file formats a Word, Excel, or PowerPoint document can be saved as. Think of these as a form of language your computer's word processor reads to spit out English back to you.

What's a file extension?

A quick summary

Text

.doc - The old Microsoft Word file format.
.docx - The new Microsoft Word file format. Saves by default.
.docm - The new Microsoft Word file format with macros enabled. Dangerous.
.odt - The OpenDocument format, used by OpenOffice, and its successor, LibreOffice.

Slideshows

.ppt - The old Microsoft PowerPoint file format.
.pptx - The new Microsoft PowerPoint file format. Saves by default.
.pptm - The new Microsoft PowerPoint file format with macros enabled. Dangerous.
.pps - The old Microsoft PowerPoint file format with automatic slideshows.
.ppsx - The new Microsoft PowerPoint file format with automatic slideshows.

Spreadsheets

.xls - The old Microsoft Excel file format.
.xlsx - The new Microsoft Excel file format. Saves by default.
.xlsm - The new Microsoft Excel file format with macros enabled. Dangerous.
.xlsb - The Excel binary format. More information to come...

Macros

In the past, it used to be a roll of the die whether a document received had viruses or not. Starting with Office 2000, Microsoft restricted running macros by default, but they were still easily enabled. With the release of Office 2007, Microsoft further locked down macro access; the new .docx, .pptx, and .xlsx files do not support macros. Instead, the corresponding macro-enabled OOXML-transitional Office document files now end in .docm, .pptm, and .xlsm.

But wait: What's OOXML? For that, we have to walk through the history of the standardization of word processor documents.

A brief history

For the sake of simplicity, we won't be covering obsolete, or uncommon file formats like those from WordPerfect or Lotus. However, Microsoft Word and Excel should be able to read and convert most of these files. No promises that there won't be errors though; these old, proprietary formats are not standardized whatsoever.

XML extensions for Office 2003

OASIS OpenDocument

Sun Microsystems had purchased a relatively obscure alternative Office suite called StarOffice. However, in an effort to stay competitive with Microsoft Office, Sun Microsystems opened up the StarOffice formats for use by everyone. Hence the rise of .odt and the standardization of OpenDoucment as an ISO format.

Currently, the most up-to-date Office suite using OpenDocument as its primary file format is LibreOffice.

OOXML Office 2007 "transitional"

... However, due to the fact that Microsoft was unable to release a version of Office compatible with the official ISO spec, Microsoft added OpenDocument support with the release of Service Pack 2 for Office 2007.

OOXML Office 2013 "strict"

Office 2013 was the first version of Office to support the official ISO OOXML specification, here called "OOXML-strict". However, due to the proliferation of "OOXML-transitional" documents, as well as the need to maintain comparability with Office 2007 and Office 2010, it isn't chosen as the default file format whenever an Office document is saved.