Early prefixes There are several
numeral prefixes in the English language that are binary prefixes, such as
bi-,
semi-,
hemi-,
di-,
tetra- and
octo-. The original
metric system adopted by France in 1795 included two binary prefixes named
double- (2×) and
demi- (×).
Ubuntu, and
Debian, have been updated to use "MB" and "GB" to denote decimal prefixes when displaying disk drive capacities and file sizes. Some manufacturers, such as
Seagate Technology, have released recommendations stating that properly-written software and documentation should specify clearly whether prefixes such as "K", "M", or "G" mean binary or decimal multipliers. The 5.25-inch diskette sold with the
IBM PC AT could hold = bytes, and thus was marketed as "1200 KB" with the binary sense of "KB". However, the capacity was also quoted "1.2 MB", which was a hybrid decimal and binary notation, since the "M" meant 1000 × 1024. The precise value was (decimal) or (binary). The 5.25-inch
Apple Disk II had 256 bytes per sector, 13 sectors per track, 35 tracks per side, or a total capacity of bytes. It was later upgraded to 16 sectors per track, giving a total of = bytes, which was described as "140KB" using the binary sense of "K". The most recent version of the physical hardware, the "3.5-inch diskette" cartridge, had 720 512-byte blocks (single-sided). Since two blocks comprised 1024 bytes, the capacity was quoted "360 KB", with the binary sense of "K". On the other hand, the quoted capacity of "1.44 MB" of the High Density ("HD") version was again a hybrid decimal and binary notation, since it meant 1440 pairs of 512-byte sectors, or = . Some operating systems displayed the capacity of those disks using the binary sense of "MB", as "1.4 MB" (which would be ≈ ). User complaints forced both Apple and Microsoft A common source of confusion was the discrepancy between the capacities of hard drives specified by manufacturers, using those prefixes in the decimal sense, and the numbers reported by operating systems and other software, that used them in the binary sense, such as the
Apple Macintosh in 1984. For example, a hard drive marketed as "1 TB" could be reported as having only "931 GB". The confusion was compounded by fact that RAM manufacturers used the binary sense too.
Legal disputes The different interpretations of disk size prefixes led to class action lawsuits against digital storage manufacturers. These cases involved both flash memory and hard disk drives.
Early cases Early cases (2004–2007) were settled prior to any court ruling with the manufacturers admitting no wrongdoing but agreeing to clarify the storage capacity of their products on the consumer packaging. Accordingly, many flash memory and hard disk manufacturers have disclosures on their packaging and web sites clarifying the formatted capacity of the devices or defining MB as 1 million bytes and 1 GB as 1 billion bytes. The
International Bureau of Weights and Measures (BIPM), which maintains the
International System of Units (SI), expressly prohibits the use of SI prefixes to denote binary multiples, and recommends the use of the IEC prefixes as an alternative since units of information are not included in the SI. == Other uses ==