Some keyboards have a "mode" key to switch between different forms of writing. This of course would only be the case on keyboards that contain more than one set of Japanese symbols. Hiragana, katakana, halfwidth katakana, halfwidth Roman letters, and fullwidth Roman letters are some of the options. A typical Japanese character is square while Roman characters are typically variable in width. Since all Japanese characters occupy the space of a square box, it is sometimes desirable to input Roman characters in the same square form in order to preserve the grid layout of the text. These Roman characters that have been fitted to a square character cell are called fullwidth, while the normal ones are called halfwidth. In some fonts these are fitted to half-squares, like some monospaced fonts, while in others they are not. Often, fonts are available in two variants, one with the halfwidth characters monospaced, and another one with proportional halfwidth characters. The name of the typeface with proportional halfwidth characters is often prefixed with "P" for "proportional".