text, font specification and document margins. Font and margin defaults, style presets and other functions vary according to program defaults. There may also be incompatibilities between different RTF versions, e.g. between RTF 1.0 1987 and later specifications, or between RTF 1.0-1.4 and RTF 1.5+ in use of Unicode characters. And though RTF supports metadata like title and author, not all implementations support this. Nevertheless, the RTF format is consistent enough to be considered highly portable and acceptable for cross-platform use. Objects Microsoft Object Linking and Embedding (OLE) objects and Macintosh Edition Manager subscriber objects allow embedding of other files inside the RTF, such as tables or charts from spreadsheet application. However, since these objects are not widely supported in programs for viewing or editing RTF files, they also limit RTF's interoperability. If software that understands a particular OLE object is not available, the object is displayed using a picture of the object which is embedded along with it. Pictures RTF supports inclusion of JPEG, PNG, Enhanced Metafile (EMF), Windows Metafile (WMF), Apple PICT, Windows device-dependent bitmap, Windows device-independent bitmap and OS/2 Metafile picture types in hexadecimal (the default) or binary format in a RTF file. Not all of these picture types are supported in all RTF readers, however. When a RTF document is opened in software that does not support the picture type of an inserted picture, the picture is not displayed. RTF writers usually either convert an inserted picture in an unsupported picture type to one in a supported picture type, or do not include picture at all. For better compatibility with Microsoft products, some RTF writers include the same picture in two different picture types in one RTF file: one supported picture type to display, and one uncompressed WMF copy of the original picture to improve compatibility with some Microsoft applications like Wordpad. This method increases the RTF file size dramatically. The RTF specification does not require this method, and several implementations do not include the WMF copy (e.g. Abiword or Ted). For Microsoft Word, it is also possible to set a specific registry value ("ExportPictureWithMetafile=0") to prevent Word from saving the WMF copy. Fonts RTF supports embedding of fonts used in the document, but this feature is not widely supported in software implementations. RTF also supports generic font family names used for font substitution: roman (serif), Swiss (sans-serif), modern (monospace), script, decorative and technical. This feature is