0x100000000ULL

0x100000000ULL is a hexadecimal literal used in C and C++ to represent the unsigned long long value 4294967296, which is 2^32. The suffix ULL specifies the type unsigned long long, ensuring the constant has at least 64 bits and cannot overflow when used in expressions with smaller integers.

In decimal, 0x100000000 equals 4,294,967,296. In hexadecimal notation, it is 1 followed by eight zeros (1 0000 0000). This value sits just beyond the 32-bit unsigned maximum, which is 0xFFFFFFFF (4,294,967,295), and it commonly marks the 32-bit boundary often associated with 4 GiB of address space.

Common uses of 0x100000000ULL include representing memory sizes or boundaries in code that must remain portable across platforms, performing 64-bit arithmetic without overflow, and as a convenient expression for shifting by 32 bits (for example, (1ULL << 32) evaluates to 0x100000000ULL). The ULL suffix helps ensure consistent type width on platforms where unsigned long long is 64 bits (such as both LP64 and LLP64 architectures), providing predictable behavior in constant expressions.

Related concepts include 0xFFFFFFFF (the 32-bit unsigned maximum) and 1ULL << 32 as an alternative way to express the same value. 0x100000000ULL is a compact tool for working with 32-bit boundaries within 64-bit contexts in systems programming and low-level software.