A yottabyte (derived from the SI prefix yotta-) is a unit of information or computer storage equal to one septillion (one long scale quadrillion or 1024) bytes. It is commonly abbreviated YB. As of 2008, no computer has yet achieved one yottabyte of storage. In fact, the combined space of all the computer hard drives in the world does not amount to even one zettabyte. According to one study, all the world's computers stored approximately 160 exabytes in 2006, with nearly 1 zettabyte projected by 2010. When used with byte multiples, the SI prefix may indicate a power of either 1,000 or 1,024, so the exact number may be either:
128-bit processors could become prevalent when 16 exbibytes of addressable memory is no longer enough (128-bit processors would allow for 274,877,906,944 yottabytes of memory).