Yb

The symbol for ytterbium. See also ytterbium.

A septillion (10 24 ) bytes. In computing and storage systems, a YB (YottaByte) is exactly 1,208,925,819,614,629,174,706,176 (2 80 ) bytes, since the measurement is based on a base 2, or binary, number system.The term YB comes from the fact that 1,208,925,819,614,629,174,706,176 is nominally, or approximately, 1,000,000,000,000,000,000,000,000, which suggests that mathematicians consider a difference of 208,925,819,614,629,174,706,176 to be a rounding error. See also byte.