A picture is represented in the document text stream as a special character, an ASCII 1 whose CHP has the fSpec bit set to 1. The file location of the picture in the Word binary file is stored in the character's CHP in chp.fcPic. The fcPic is a byte offset into the data stream. Beginning at the position recorded in chp.fcPic, a header data structure, the PIC, will be stored. If the picture is a reference to a TIFF file, a Picture file or an Office shape file, the name of the file will be recorded immediately following the PIC in a Pascal style string. If the picture is an Office shape, a Window's metafile or a bitmap, the shape, metafile or bitmap will immediately follow the PIC. Pictures that are a reference to an Office shape file will include both the filename and the shape in that order. Pictures inserted with Word97 are in the new Office shape format (documented elsewhere). However, pictures can be copied from older files into newer ones and their old format will persist until the picture is edited or displayed.
Some files (including all files created by Word for the Macintosh) may store Macintosh PICT pictures as well. In this case, the PIC structure is immediately followed by a standard Windows metafile depicting a large "x", so that older readers expecting only a metafile after the PIC will just display this "x". If a reader detects this standard "x" metafile, it can extract the sizes of the standard "x" metafile and the Macintosh PICT picture that follows it from an early portion of this "x" metafile. Please see Appendix B for a discussion of this technique.