Byte, kilobyte, megabyte, gigabyte, terabyte & petabyte
1 Byte (B) = 8 bits (b) which can describe 256 discrete values (brightness, colour, etc.).
Traditionally, just as computer-folk like to start counting from zero, they also ascribe 2 raised to the power 10, 20, 30 etc. (210,220,230 etc.) to the values kilo, mega, giga, etc. which become, 1,024, 1,048,576, 1,073,741,824 etc. This can be difficult to handle for those drilled only in base-10 mathematics. Fortunately, disk drive manufacturers, who have to deal in increasingly vast numbers, describe their storage capacity in powers of 10, so a 20 GB drive has 20,000,000,000 bytes capacity. Observation suggests both systems are continuing in use… which could lead to some confusion.
Currently 3.5-inch hard disk drives store from 20-180 GB. Solid-state store chips, DRAMs, increment fourfold in capacity every generation, hence the availability of 16, 64, and now 256 Mb chips (ie 256 x 220).
A full frame of digital television, sampled at 8 bits according to ITU-R BT.601, requires just under 1 MB of storage (830 kB for 625 lines, 701 kB for 525 lines). HDTV frames are around 5–6 times larger and 2k digital film frames sampled at 10 bits are 12 MB.