A fallback font is a reserve typeface containing symbols for as many Unicode characters as possible. When a display system encounters a character that is not part of the repertoire of any of the other available fonts, a symbol from a fallback font is used instead. Typically, a fallback font will contain symbols representative of the various types of Unicode characters. Systems that do not offer a fallback font typically display black or white rectangles, question marks, the Unicode Replacement Character (U+FFFD), or nothing at all, in place of missing characters. Placing one or more fallback fonts at the end of a list of preferred fonts ensures that there are no missing characters. Unicode BMP Fallback font 0 0 2 0 The Unicode BMP Fallback font is a Unicode font that was originally created for debugging purposes. It contains a glyph for every character in the Unicode Basic Multilingual Plane. Each glyph consists of a box containing the four hexadecimal digits corresponding to the Unicode value. The example to the left is a mock-up of the glyph for a space character (U+0020). Unlike the Unicode Last Resort font, the Unicode BMP Fallback font displays a different glyph for each different Unicode character, but cannot display all Unicode characters. Because four hexadecimal digits can only represent 64K characters (0000=0, FFFF=65,535) the Unicode BMP Fallback is limited to the 64K characters in the Unicode Basic Multilingual Plane. Unicode Last Resort font As of Unicode version 5.0, the Unicode consortium provides a fallback font to represent types of Unicode characters. This is a version of the macOS Last Resort system font, modified to work on non-Apple platforms and made available by Apple via the Unicode Consortium. The symbols provided by the Unicode Last Resort font place glyphs into categories based on their location in the Unicode system and provide a hint to the user about which font or script is required to view the unavailable characters. The symbols provided by the Unicode Last Resort font are square with rounded corners with a bold outline. In the left and right sides of the outline, the Unicode range that the character belongs to is given using hexadecimal digits. Top and bottom are used for one or two descriptions of the Unicode block. A symbol representative of the block is centered inside the square. Unlike the Unicode BMP Fallback font or the GNU Unifont, the Unicode