One thing you may have noticed by now is that the normally metric prefixes (kilo-, mega-, giga-, and tera-) have mysteriously turned into binary prefixes. This has been the conventional naming all along, so gradually, people got used to it. Nonetheless, many non-geeks have been baffled by the unusual prefix use. To clear up the confusion, the International Electrotechnical Commission (IEC) approved a set of new prefixes for binary multiples:
| Metric name | Metric abbr. | Definition | IEC name | IEC abbr. | Definition |
|---|---|---|---|---|---|
| Kilobyte | KB | 103B=1000B | Kibibyte | Ki | 210 B=1024B |
| Megabyte | MB | 106B=1000KB | Mebibyte | Mi | 220 B=1024Ki |
| Gigabyte | GB | 109B=1000MB | Gibibyte | Gi | 230 B=1024Mi |
| Terabyte | TB | 1012B=1000GB | Tebibyte | Ti | 240 B=1024Gi |
Under the new definitions, kilo-, mega-, giga- and tera- retain their metric definitions, while kibi-, mebi-, gibi- and tebi- represent the base-two values. The idea never caught on... well, nearly never. Many companies insist on using the new definitions to make the memory sizes of their devices look larger. When you see a 1 TB devices, chances are, it's only 1012B and not 240B.