| Kilooctets (ko) | Exbibits (Eibit) |
|---|---|
| 1 Kilooctet | 6.93889390391 × 10-15 Eibit |
| 2 Kilooctets | 1.38777878078 × 10-14 Eibit |
| 3 Kilooctets | 2.08166817117 × 10-14 Eibit |
| 4 Kilooctets | 2.77555756156 × 10-14 Eibit |
| 5 Kilooctets | 3.46944695195 × 10-14 Eibit |
| 10 Kilooctets | 6.93889390391 × 10-14 Eibit |
| 20 Kilooctets | 1.38777878078 × 10-13 Eibit |
| 25 Kilooctets | 1.73472347598 × 10-13 Eibit |
| 50 Kilooctets | 3.46944695195 × 10-13 Eibit |
| 100 Kilooctets | 6.93889390391 × 10-13 Eibit |
| Reference | Kilooctets (ko) | Exbibits (Eibit) |
|---|---|---|
| A plain text message (160 characters) | 0.16 ko | 1.11022 × 10-15 Eibit |
| A three-minute MP3 | 3000 ko | 2.08167 × 10-11 Eibit |
| A smartphone photo | 4000 ko | 2.77556 × 10-11 Eibit |
| A high-definition film | 4000000 ko | 0.0000000277556 Eibit |
| A dual-layer Blu-ray disc | 50000000 ko | 0.000000346945 Eibit |
The kilooctet is a unit of digital information equal to one thousand octets, and therefore to eight thousand bits. Its symbol is ko. It is the smallest of the everyday storage units, and for two decades it was the unit in which the whole capacity of a computer was described.
A kilooctet holds a thousand characters of unaccented text, which is about two hundred words, or a third of a page. The plain-text file of a short letter is a few kilooctets. Almost nothing else in modern computing is this small: an empty document from a word processor is already tens of kilooctets, because the file format carries formatting, fonts and metadata around the text.
The historical importance of the unit is hard to overstate. The Apple II shipped with 4 kilooctets of memory, the Commodore 64 was named for its 64, and the first IBM personal computer could address 640. Programs of real complexity — spreadsheets, word processors, games with graphics and sound — were written to fit inside those numbers, which required a discipline that has largely disappeared.
The kilooctet is also where the decimal and binary confusion began. Memory came in 1,024-octet units because addressing is binary, and everyone called that a kilooctet. Disc manufacturers counted in true thousands. The two conventions differ by 2.4 per cent, which was negligible at this scale, but the same error compounds at each step upward and reaches 10 per cent by the teraoctet.
The IEC resolved the ambiguity in 1998 by defining the kibioctet as 1,024 octets and leaving the kilooctet at exactly 1,000. Operating systems have adopted this unevenly: some report file sizes in true kilooctets, others still divide by 1,024 while writing ko, and a few now write Kio correctly.
Where the unit still appears daily is in network protocols and in the sizes of small resources on the web. A web page's stylesheet, an icon, a certificate, a configuration file, a database index page — all of these are measured in kilooctets, and the standard memory page on most processors is 4 kibioctets, close enough to 4 kilooctets for casual conversation but not for arithmetic.
One kilooctet equals 1,000 octets, 8,000 bits, 8 kilobits, or about 0.9766 kibioctets.
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.