u64

u64 is a name used for a 64-bit unsigned integer type in several programming languages, most commonly associated with Rust, where it denotes a distinct primitive type. It represents non-negative integers and is used when a value must range from zero up to the maximum of 2^64 minus one. In other languages the corresponding type may be named uint64_t, unsigned long long, or simply u64 depending on the language.

Size, range, and representation: as an 8-byte value, u64 can hold integers from 0 to 18,446,744,073,709,551,615. In memory the value is stored as binary data; the byte order in memory is subject to the machine’s endianness, while the logical value is endianness-agnostic for arithmetic.

Operations and behavior: u64 supports standard arithmetic and bitwise operations. Overflow behavior is language-specific: some environments wrap around modulo 2^64, while others may detect overflow and raise an error or panic. Conversions between u64 and other numeric types typically require explicit casting or conversion functions to prevent data loss or sign confusion.

Usage and considerations: u64 is well suited for large counters, IDs, timestamps in nanoseconds, or bit-field manipulations where non-negative values are required. It is often chosen over smaller widths to avoid overflow in extensive computations. When interoperating with external data formats or languages, care is needed to maintain consistent endianness and to handle conversions from signed or larger integers.

See also: u32, u128, uint64_t, unsigned integer, endianness.