Quadruple-precision floating-point format

In computing, quadruple precision (or quad precision) is a binary floating-point–based computer number format that occupies 16 bytes (128 bits) with precision at least twice the 53-bit double precision. This 128-bit quadruple precision is designed for applications needing results in higher than double precision, and as a primary function, to allow computing double precision results more reliably and accurately by minimising overflow and round-off errors in intermediate calculations and scratch variables.

Source: Wikipedia — Quadruple-precision floating-point format (CC BY-SA 4.0)