Conversion from 4 Gibioctets to Octets

Information about the Gibioctet (Gio)

The gibioctet is a unit of digital information equal to 1,073,741,824 octets, which is 1,024 mebioctets. Its symbol is Gio. It is the binary counterpart of the gigaoctet, and the 7.4 per cent difference between them is the single most common cause of confusion about data units.

This is the unit in which computer memory is actually sold, whatever the packaging says. A module labelled 8 GB holds 8 gibioctets, which is 8.59 gigaoctets. It could not hold anything else: memory addressing is binary, and a module with a decimal capacity would leave part of its address range unpopulated. The label is a convenient shorthand rather than a measurement.

Storage, by contrast, is genuinely decimal. A drive sold as 500 gigaoctets holds five hundred thousand million octets, and the operating system divides that by 1,024 three times and reports 465.7 gibioctets. The two figures describe the same hardware. Neither party is being dishonest; they are simply counting in different bases, and the labelling convention differs by industry.

Cloud computing has made the distinction visible in contracts. Virtual machine sizes, container memory limits and the parameters that control how much memory a program may use are all specified in gibioctets, because they map onto real memory pages. A limit of 4 GB set in a decimal-minded tool and 4 GiB set in a binary one differ by nearly three hundred megaoctets, which is enough to change whether a program runs.

For everyday scale, a gibioctet holds about a thousand books as plain text, a few hundred photographs, or twenty minutes of high-definition video. It is roughly what a modern web browser occupies in memory with a dozen pages open, which is a fair illustration of how the standard for what counts as a small amount has moved.

The correct symbol is Gio, and it appears in system tools, in virtualisation documentation and in standards. Where a document writes GB for memory, the safe reading is gibioctets; where it writes GB for a disc or a network, the safe reading is gigaoctets. The habit of checking which is meant costs a second and prevents a seven per cent error.

One gibioctet equals 1,073,741,824 octets, 1,024 mebioctets, 8 gibibits, or about 1.074 gigaoctets.

Information about the Octet (octet)

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.