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In computer typography, modern outline fonts describe printable characters (glyphs) by cubic or quadratic mathematical curves with control points. Nevertheless, bitmap fonts are still in use. Converting outlines requires filling them in; converting to bitmaps is not trivial, because bitmaps often don't have sufficient resolution to avoid "stairstepping" ("aliasing"), especially with smaller visible character sizes. Processing outline character data in a sophisticated fashion to create satisfactory bitmaps for rendering is called "hinting". Although the term implies suggestion, the process is deterministic and done by executable code, essentially a special-purpose computer language. While automatic hinting is possible, results can be inferior to that done by experts.