0U

0u is a decimal integer literal that uses a type-suffix to indicate unsigned value. In languages that support numeric literal suffixes, the letter u (or U) after a numeric literal designates an unsigned type. The value of 0u is zero, but its type is unsigned int by default in languages like C and C++, unless a wider unsigned type suffix is added (for example 0uL for unsigned long).

In practical use, 0u is used to ensure unsigned arithmetic or to make constant expressions match an unsigned type in assignments, templates, or function overloads. This can affect how arithmetic and comparisons behave, particularly in edge cases involving overflow or sign promotion. For example, using 0u in expressions with signed integers can prevent accidental promotion to signed types.

Common variations include different suffix combinations to select wider unsigned types, such as 0u for unsigned int, 0uL for unsigned long, or 0uLL for unsigned long long in languages that support these forms. The exact width associated with each suffix depends on the language standard and the target platform.

Other languages with similar conventions may use the same or different suffix letters. While 0 by itself is a signed zero in many contexts, 0u is explicitly unsigned, making its behavior explicit in mixed-type expressions or tightly scoped constant definitions. See also numeric literals, unsigned integers, and literal suffixes.