RTF

RTF (usually referred to as such) stands for Rich Text Format, a file format developed by Microsoft that most text processing program are able to read and write.

External links:

Official RTF Spec via FTP - in many formats including HQX, manpages, rtf, PS. Also info on RTF to something translators. Includes versions 1.3 and 1.5.

RTF Spec via Web (Same as above)

RTF Spec for Word 97 features - you will also need the full version 1.4 of the RTF spec.

A link to the RTF v1.3 spec

Online version of spec (HTML)