0UL

0uL is a numeric literal used in the C and C++ programming languages. It represents the value zero as an unsigned long integer. The literal is formed by the digits 0 followed by the suffixes 'u' (unsigned) and 'l' or 'L' (long). The letters can appear in either order, so 0uL, 0Ul, 0UL, and 0Lu are all valid and equivalent in value and type.

The type of 0uL is unsigned long. This distinguishes it from 0 (an int), 0L (a long), or 0UL (another valid form with the same meaning). Using 0uL can be useful to force an expression to be evaluated with unsigned long semantics, which can affect overload resolution, template deduction, or arithmetic behavior, especially in code that must avoid signed overflow or must match function parameters that expect unsigned long.

Portability notes: the width of unsigned long varies by platform (for example, 32-bit on some Windows platforms and 64-bit on many Unix-like systems). While the value remains zero, the underlying type may differ, which can influence binary interfaces and certain arithmetic operations.

Example: unsigned long a = 0uL; unsigned long b = a + 1; In both cases the constants are of type unsigned long, ensuring consistency with related code that uses unsigned arithmetic.