| Exbioctets (Eio) | Kilobits (kbit) |
|---|---|
| 1 Exbioctet | 9.22337203685 × 1015 kbit |
| 2 Exbioctets | 1.84467440737 × 1016 kbit |
| 3 Exbioctets | 2.76701161106 × 1016 kbit |
| 4 Exbioctets | 3.68934881474 × 1016 kbit |
| 5 Exbioctets | 4.61168601843 × 1016 kbit |
| 10 Exbioctets | 9.22337203685 × 1016 kbit |
| 20 Exbioctets | 1.84467440737 × 1017 kbit |
| 25 Exbioctets | 2.30584300921 × 1017 kbit |
| 50 Exbioctets | 4.61168601843 × 1017 kbit |
| 100 Exbioctets | 9.22337203685 × 1017 kbit |
| Reference | Exbioctets (Eio) | Kilobits (kbit) |
|---|---|---|
| A plain text message (160 characters) | 1.38778 × 10-16 Eio | 1.28 kbit |
| A three-minute MP3 | 2.60209 × 10-12 Eio | 24000 kbit |
| A smartphone photo | 3.46945 × 10-12 Eio | 32000 kbit |
| A high-definition film | 0.00000000346945 Eio | 32000000 kbit |
| A dual-layer Blu-ray disc | 0.0000000433681 Eio | 400000000 kbit |
The exbioctet is a unit of digital information equal to two to the sixtieth power octets, which is 1,024 pebioctets. Its symbol is Eio. It is the binary counterpart of the exaoctet, and the two differ by 15.3 per cent.
One number involving this unit is quoted more than any other: sixteen exbioctets, the size of the address space a 64-bit processor can reach. Two to the sixty-fourth octets is 16 EiB, and that figure is the theoretical ceiling on the memory of every machine built on the architecture that has dominated computing since the mid-2000s.
The same limit reappears in filesystems. A filesystem that numbers its blocks with 64-bit values can address 16 exbioctets of blocks, and several modern designs state exactly that as their maximum volume size. Others state 8 exbioctets, having reserved one bit for a sign or a flag — a detail that halves the limit and is worth knowing when reading a specification.
Nothing approaches these sizes in practice. The largest storage systems in the world hold exaoctets, and the total of all data held by humanity is a few hundred zettaoctets, which is tens of thousands of exbioctets. The 64-bit ceiling was chosen precisely so that it would not be reached, and the transition from 32 bits, whose four-gibioctet limit was reached within a decade, is why the designers left so much room.
An exbioctet is 1,152,921,504,606,846,976 bits and 128 pebioctets. It is a quantity that exists in specifications, in address arithmetic and in the design documents of large systems, and nowhere else. Describing it in terms of photographs or films is not useful, because no collection of either comes close.
The symbol Eio and its decimal sibling Eo differ by more than an eighth, which is far too much to leave to inference. When a document writes EB in the context of an address space, it almost certainly means EiB, because address spaces are powers of two by construction; when it writes EB about stored data, it almost certainly means the decimal unit.
One exbioctet equals 1,024 pebioctets, 1,152,921,504,606,846,976 octets, 8 exbibits, or about 1.153 exaoctets.
The kilobit is a unit of digital information equal to one thousand bits. Its symbol is kbit. The lowercase k matters: it marks the decimal kilo of the metric system, one thousand exactly, as distinct from the binary 1,024 that the capital K sometimes indicated in older computing usage.
That distinction was fought over for decades. Memory is built in powers of two, so a chip holding 1,024 bits was called a kilobit chip, and the name stuck even though the number was wrong by 2.4 per cent. Storage and transmission, meanwhile, always counted in true thousands. The IEC settled the matter in 1998 by naming the binary quantity a kibibit, leaving the kilobit to mean one thousand and nothing else.
For a sense of scale, a kilobit holds 125 octets, which is about 125 characters of unaccented text — roughly a long sentence, or the length of a short social-media post. A single low-resolution photograph is thousands of times larger. The kilobit is a unit for things that were once considered generous and are now considered trivially small.
Its historical home was the telephone modem. Dial-up connections were rated in kilobits per second, and the numbers marked the era precisely: 300 bits per second in the late 1970s, then 1.2, 2.4, 9.6, 14.4, 28.8 and finally 56 kilobits per second, the last of which pushed an ordinary voice line to its theoretical ceiling. Anyone who used the internet before broadband measured their experience in these numbers.
The kilobit survives in audio and video encoding, where bit rates are quoted in kilobits per second. Speech codecs used in telephony run from 8 to 64. Music encoded at 128 kilobits per second was the early standard for portable players, 192 and 256 are common now, and 320 is the practical ceiling for the older lossy formats. Video runs a decimal order higher, in megabits.
Memory chip capacities are still occasionally described in kilobits, particularly for small serial memories used in embedded devices, where a 64-kilobit part holds 8 kilooctets of configuration data. In those specifications the figure is usually the binary one, so the datasheet is worth reading carefully.
One kilobit equals 1,000 bits, 125 octets, or about 0.9766 kibibits.