Bit

From Memory Alpha, the free Star Trek reference

A bit (an acronym standing for Binary digIT) is a unit of information storable in a computer. It is commonly represented as a zero (0) or one (1).

The Soong-type android Data was built with the ultimate storage capacity of eight hundred quadrillion (800 x 10¹⁵) bits. (TNG: "The Measure Of A Man")

At 8 bits per byte, it can be calculated that Data has 100 petabytes of memory.