JIS X 0208 - Code Structure - Unassigned Code Points

Among the 2-byte codes, rows 9 to 15 and 85 to 94 are unassigned code points (空き領域, aki ryōiki?); that is, they are code points with no characters assigned to them. Also, some cells in other rows are also essentially unassigned code points.

These empty areas contain code points that should basically not be used. Except when there is prior agreement among the relevant parties, characters (gaiji) for information interchange should not be assigned to the unassigned code points.

Even when assigning characters to unassigned code points, graphic characters defined in the standard should not be assigned to them, and the same character should not be assigned to multiple unassigned code points; characters should not be duplicated in the set.

Furthermore, when assigning characters to unassigned code points, it is necessary to be cautious of unification in regards to kanji glyphs. For example, row 25 cell 66 corresponds to the kanji meaning “high” or “expensive”; both the form with the character meaning “mouth” (口) in the middle (高) and the less common form with a ladder-like construction (髙) are subsumed into the same code point. Consequently, limiting point 25-66 to the “mouth” form and assigning the latter “ladder” form to an unassigned code point would technically be in violation of the standard.

Read more about this topic:  JIS X 0208, Code Structure

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