From Mac Guides
TextEdit is a text editor included with Mac OS X. It is much more powerful than its predecessor, SimpleText, and its Windows counterpart, NotePad, yet lacks the advanced features of a commercial word processor. Many of its numerous features are gained simply by being written in Cocoa, such as spell checking, a ruler and even an elementary WYSIWYG html editor. TextEdit can read and write plain text files, Rich Text Format (RTF), HTML, Word format and Word XML format.
TextEdit's source code is included with the Mac OS X Developer Tools. As of Mac OS X 10.4 (Tiger), the project files are located in /Developer/Examples/AppKit/TextEdit/ when the Developer Tools are installed.
- By default, TextEdit saves documents in rich text format. This is unsuitable for some situations, such as when creating a hand-coded html file. As a solution, a document can be converted to plain text by choosing Format > Make Plain Text. Alternatively, you can set TextEdit to create all new documents as plain text by setting the new document format to "Plain Text" in the preferences.