Unicode input

Unicode input is the insertion of a specific Unicode character on a computer by a user; it is a common way to input characters not directly supported by a physical keyboard. Unicode characters can be inserted in three ways: from the screen by means of an applet from which one can select the character, by pasting from the operating system's clipboard, or by typing a certain sequence of keys on a physical keyboard. Unicode is similar to ASCII, but provides many more options and can store more signs.

A Unicode input system needs to provide a large repertoire of characters, ideally all valid Unicode code points. This is different from a keyboard layout which defines keys and their combinations only for a limited number of characters appropriate for a certain locale.

Unicode characters are distinguished by code points, which are conventionally represented by the letter U followed by four or five hexadecimal digits, for example U+00AE or U+1D310. Characters in the Basic Multilingual Plane (BMP), containing modern scripts – including many Chinese and Japanese characters – and many symbols, have a 4-digit code. Historic scripts, but also many modern symbols and pictographs (such as emoticons, playing cards and many CJK characters) have 5-digit codes.

In some applications on Microsoft Windows, particularly those using the RichEdit control, decimal Unicode code points (for example, 256 for U+0100) are supported with Alt codes.

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