uint64

uint64 is an unsigned 64-bit integer type used in several programming languages. It stores non-negative whole numbers in a fixed width of 64 bits, allowing values from 0 to 2^64−1. The exact type name varies by language (for example uint64 in Go, u64 in Rust and Zig). In C and C++, a 64-bit unsigned integer is typically provided as uint64_t via the stdint.h header.

On modern hardware, it occupies eight bytes of memory. The value range is 0 to 18,446,744,073,709,551,615. In binary, these values correspond to all patterns from all-zeroes to all-ones. Endianness affects how the bytes are laid out in memory or in network serialization, not the abstract value.

Arithmetic on uint64 values is generally modulo 2^64, so adding one to the maximum value wraps to zero. Subtraction, multiplication, and division follow the same wraparound behavior in typical implementations. Some languages provide overflow checks in debug mode or offer explicit checked arithmetic. Conversions from signed integers or floating-point numbers may require explicit casting and can lose information if out of range, and moving from a larger unsigned type to a smaller one can truncate data.

Common uses include counters, array indices, file sizes, protocol fields, and unique identifiers where a large non-negative range is required. When interoperating with other systems, it is important to agree on endianness and to use a standard representation such as 64-bit unsigned integers in network byte order where appropriate. Related types include uint32 and other fixed-width unsigned integers, and the signed counterpart int64 in languages that distinguish signed and unsigned forms.