txt From the 70's to 2007 the open source .txt filename extension format commonly referred to plain text documents encoded using the ASCII character set. To support internationalization and localization, .txt text documents are today text files encoded using the UTF-8 or UTF-16LE standard which is a superset of the ASCII character set. Text documents of type .txt typically have minimal formatting for example no support for bold or italic characters or support for bullet points etc. This allows .txt documents to use minimum storage space and be platform independent as long as the operating system supports the underlying encoding character set used to create the .txt document. On windows .txt file support has existed since 1985 when Windows 1.0 was released and since then has been mostly associated with the notepad application on Microsoft Windows.
lrf The LRF format is a proprietary format developed by Sony in collaboration with Canon, as a document and text encoding standard for the Broad Band eBook file format. The format specifically targeted Sony portable eBook readers and was capable of encoding both text, pagination, and images. Being unencrypted, LRF encoded files do not enforce DRM. This is in contrast to the LRX format which is also part of the BBeB eBook file format which does support encryption for DRM files. The Sony eBook store announced in July 2010 a discontinuation of support for the LRF format in favor of the public and open EPUB format.