Changes When Uppercased

Changes When Uppercased is a binary character attribute that indicates whether a given character’s uppercase mapping differs from its original code point. For most letters, this is true, as they have distinct uppercase forms, but it is also true for certain characters like the Greek final sigma, which becomes a standard sigma, or characters with no simple uppercase counterpart, such as some modifiers or digits. The property is used in case-insensitive matching and text normalization, ensuring that operations like case folding or searching ignore cases correctly. When false, the character remains unchanged under uppercase conversion, meaning its uppercase equivalent is itself. This distinction is crucial for accurately implementing locale‑independent algorithms, as it helps identify characters that require transformation versus those that do not, without relying on external casing rules.