Trial-Use Standard for Prefixes for Binary Multiples
|Publication Date:||11 December 2002|
Modern computers use binary logic for computation and addressing, and binary logic inevitably leads to addresses expressed in binary arithmetic. The size of such an address space is inevitably a power of two. Thus, when computer memories and disks were tiny (in terms of capacity), it became common practice to use "kilo" as a prefix denoting multiplication by 1024 (= 210 ). In the 1960s and 1970s this created no problem because there is not much difference between 1000 and 1024, and within the community of persons who used computers, everybody understood what was meant. Thus decimal prefixes came to be applied on the grounds that it would have been senseless, in the computer field, to interpret them as anything other than binary multiples, i.e., it would have seemed illogical to size a small memory in multiples of 1000 when the size of the address space was 1024. As the capacity of memories and disks has grown larger, the issue of correspondence with the size of the address space became less important than the issue of total capacity requirements. In addition, the disparity between binary and decimal multiples is larger with the larger prefixes. Data storage specialists now work with terabytes. If one purchases a terabyte of storage, can one store 1012 bytes or 240 bytes? The difference is roughly 10%.
Personal computers have become ubiquitous in the twenty-first century, and the use of decimal prefixes where binary multiplication is intended causes real confusion. Most computer users today are not specialists. They know that a kilometer is 1000 meters and, having no familiarity with powers of 2, assume that a kilobyte is 1000 bytes. The result is confusion and occasional misunderstanding. This IEEE standard defines new prefixes for binary multiples and thereby makes precise and unambiguous communication possible. A similar standard, IEC 60027-2 [B1], has already been adopted by the International Electrotechnical Commission.
This standard defines names and letter symbols for prefixes that denote multiplication of a unit by the binary multiplier 210n, where n = 1, 2, 3, 4, 5, or 6. Although the prefixes may be used with all units in all fields where multiplication by a binary multiplier is found to be appropriate, their primary use is in the field of information technology. The prefixes given here have also been adopted by the International Electrotechnical Commission, IEC 60027-2 [B1].1