For a fixed pitch font, this width translates to a display width of either one half or a whole unit width. It is customarily the height of the letter 'M', but since in East Asian fonts the standard character cell is square, it is the same as the unit width . Further, the same information is useful in creating correct transcoding tables for East Asian character sets. This Unicode Technical Report does not provide rules or specifications of how this property might be used in font design or line layout, since, while a useful property for this purpose, it is only one of several character properties that would need to be considered. In the Unicode Standard, no such distinction is made, but understanding the distinction is often necessary when interchanging data with legacy systems, especially when fixed size buffers are involved.
Some characters behave differently in East Asian context than in non-East Asian content.
Their default width property is considered ambiguous and needs to be resolved into an actual width property based on context. For any given operation, these six default properties resolve into only two property values narrow and wide, depending on context. All terms not defined here shall be as defined in the Unicode Standard. East Asian Width - in the context of interoperating with East Asian legacy character encodings and implementing East Asian typography, character width is an abstract concept. It can take on two values, narrow and wide .