A graphic file format developed by Aldus and Microsoft, it's used for still-image bitmaps. TIFs are stored in tagged fields, and programs use the tags to accept or ignore fields, depending on the application. You may encounter a TIF if someone e-mails you a picture in that format. (Other file types include BMP, EPS, GIF, JPG, PCT, PSD.) The shorter file extension, TIF (without the second "F"), is used for PC-based TIFF files. TIFF stands for "Tagged Image File Format."