which can contain any 8-bit values. Human readability RTF is a data format for saving and sharing documents, not a markup language; it is not intended for intuitive and easy typing. Nonetheless, unlike many word processing formats, RTF code can be human-readable. When an RTF file containing mostly Latin characters without diacritics is viewed as a plain text file, the underlying ASCII text is readable, provided that the author has kept formatting concise. When RTF was released, most word processors used binary file formats; Microsoft Word, for example, used the .DOC file format. RTF was unique in its simple formatting control which allowed non-RTF aware programs like Microsoft Notepad to open and provide readable files. Today, most word processors have moved to XML-based file formats (Word has switched to the .docx file format). Regardless, these files contain large amounts of formatting code, so are often ten or more times larger than the corresponding plain text. To be standard-compliant RTF, non-ASCII characters must be escaped. Thus, even with concise formatting, text that uses certain dashes and quotation marks is less legible. Latin languages with many diacritics are particularly difficult to read in RTF, as they result in substitutions like \'f1 for ñ and \'e9 for é. Non-Latin scripts are illegible in RTF — \u21563, for example, is used for 吻. From the beginning, RTF has also supported Microsoft OLE embedded objects and Macintosh Edition Manager subscriber objects, which are not human-readable. Common uses and interoperability Most word processing software support either RTF format importing and exporting for some RTF specification or direct editing, which makes it a "common" format between otherwise incompatible word processing software and operating systems. Most applications that read RTF files silently ignore unknown RTF control words. These factors contribute to its interoperability, though it is still dependent on the specific RTF version in use. There are several consciously designed or accidentally born RTF dialects. RTF is the internal markup language used by Microsoft Word. Since 1987, RTF files have been able to be transferred back and forth between many old and new computer systems (and now over the Internet), despite differences between operating systems and their versions. This makes it a useful format for basic formatted text documents such as instruction manuals, résumés, letters, and modest information documents. These documents, at minimum, support bold, italic and underline text formatting. Also typically supported are left-, center- and right-aligned