| Exbibits (Eibit) | Octets (octet) |
|---|---|
| 1 Exbibit | 1.44115188076 × 1017 octet |
| 2 Exbibits | 2.88230376152 × 1017 octet |
| 3 Exbibits | 4.32345564228 × 1017 octet |
| 4 Exbibits | 5.76460752303 × 1017 octet |
| 5 Exbibits | 7.20575940379 × 1017 octet |
| 10 Exbibits | 1.44115188076 × 1018 octet |
| 20 Exbibits | 2.88230376152 × 1018 octet |
| 25 Exbibits | 3.6028797019 × 1018 octet |
| 50 Exbibits | 7.20575940379 × 1018 octet |
| 100 Exbibits | 1.44115188076 × 1019 octet |
| Reference | Exbibits (Eibit) | Octets (octet) |
|---|---|---|
| A plain text message (160 characters) | 1.11022 × 10-15 Eibit | 160 octet |
| A three-minute MP3 | 2.08167 × 10-11 Eibit | 3000000 octet |
| A smartphone photo | 2.77556 × 10-11 Eibit | 4000000 octet |
| A high-definition film | 0.0000000277556 Eibit | 4 × 109 octet |
| A dual-layer Blu-ray disc | 0.000000346945 Eibit | 5 × 1010 octet |
The exbibit is a unit of digital information equal to two to the sixtieth power bits, which is 1,024 pebibits. Its symbol is Eibit. It is the binary counterpart of the exabit, and the two now differ by 15.3 per cent.
Two to the sixtieth is a number with a particular importance in computing, because sixty is close to the sixty-four bits of a modern processor address. A 64-bit machine can address sixteen exbioctets of memory, and that figure — 16 EiB — is the theoretical ceiling of the entire architecture. It appears in processor manuals, in operating system documentation and in the specification of every 64-bit filesystem.
No machine comes close to using that range. Current processors implement only forty-eight or fifty-seven of those sixty-four address bits, because wiring the full width would cost silicon for an address space nobody can fill. The unused bits are reserved, and widening the implementation is a straightforward matter whenever memory sizes make it worthwhile, which is the point of having chosen sixty-four in the first place.
An exbibit is 144,115,188,075,855,872 octets, or 128 pebioctets. That is more storage than any single organisation holds, and comparable to the combined annual output of a large part of the storage industry. As with all the larger binary units, it describes limits and capacities in specifications rather than anything that has been built.
The unit is also where filesystem designers set their maximum sizes. Filesystems built around 64-bit block pointers naturally have limits at exact powers of two, and several widely deployed ones specify maximum volume sizes in exbioctets. Those numbers are not aspirations; they are the arithmetic consequence of the pointer width, and they will hold until the architecture changes.
Reading the symbol correctly matters here. Eibit is the exbibit; Ebit is the exabit; EB and EiB are the octet forms of each. In a document where a fifteen per cent difference is significant — and at this scale it always is — the presence or absence of the lowercase i carries the entire meaning.
One exbibit equals 1,024 pebibits, 144,115,188,075,855,872 octets, or about 1.153 exabits.
The octet is a unit of digital information equal to exactly eight bits. Its symbol is octet, and its name comes from the Latin for a group of eight. It is the unit in which nearly all stored data is counted, and the reason it is called an octet rather than a byte is worth knowing.
A byte was originally the number of bits a machine used to hold one character, and that number was not fixed. Early computers used six-bit bytes, some used seven, and a few used nine. The IBM System/360 of 1964 settled on eight and its commercial success made eight the norm, but the word byte kept its older, machine-dependent meaning in specifications where ambiguity was dangerous.
The networking world therefore adopted octet. When a protocol standard says a header field is four octets long, no reader anywhere can interpret that as anything but thirty-two bits. The internet standards published by the IETF use octet throughout for exactly that reason, and French, Romanian and several other languages adopted the word for ordinary use as well, so that a hard disc sold in France is measured in gigaoctets.
Eight bits hold 256 distinct values, which is why so many things come in units of 256. A colour channel runs from 0 to 255. An IPv4 address is four octets, written as four numbers each between 0 and 255. The original ASCII character set used seven bits, leaving one spare, and the various eight-bit extensions that followed each filled that spare bit with a different set of accented letters — the mess that Unicode eventually replaced.
Modern text encoding still counts in octets. UTF-8 uses one octet for the unaccented Latin alphabet, two for most European accented letters and Greek and Cyrillic, three for Chinese, Japanese and Korean, and four for the rest. That is why the same sentence occupies different amounts of storage in different languages, and why a text-length limit measured in octets is not a limit on characters.
Storage capacity, file sizes, memory and network payloads are all quoted in octets or their multiples. Transmission rates are the exception, being quoted in bits per second, and the factor of eight between the two conventions is the single most common source of confusion in the field.
One octet equals 8 bits, 0.008 kilobits, or 0.001 kilooctets.