80bit

80-bit refers to a data size equal to 80 bits, i.e., 10 bytes. It is not a common fixed-width integer in mainstream modern architectures, but it appears in specialized computing contexts where ten-byte fields or extended precision representations are needed, such as certain floating-point formats and legacy cryptographic materials.

The most notable 80-bit format is the x87 extended precision floating-point representation used by Intel x86 CPUs. It encodes numbers with 1 sign bit, 15 exponent bits, and an explicit 1-bit integer part plus 63 fraction bits, totaling 80 bits. This yields a 64-bit significand precision. Values can be kept in 10-byte registers, but when stored in memory or passed to languages that do not support extended precision, they are often converted to 64-bit doubles, which reduces the precision to fit standard types.

In cryptography, some legacy systems used 80-bit keys or parameters. While adequate in earlier times, 80-bit security is widely considered insufficient today, and modern standards favor 128-bit or higher security margins. Consequently, 80-bit keys are typically deprecated in new designs and protocols.

In programming and data formats, 80-bit values are uncommon; most languages support 8-, 16-, 32-, 64-, or 128-bit widths. Ten-byte fields may occur in file formats or network protocols to store certain numeric values or identifiers, reflecting the 80-bit size but not a native integer type.

The term 80-bit is sometimes used to refer to ten bytes of data or to the 80-bit floating-point format, and it contrasts with other fixed sizes (8, 16, 32, 64, 128).