Kilo, Mega, Giga, Tera, Peta, Exa, Zetta belong to the list of binary prefixes used to indicate quantity or capacity, such as a byte or bit in computing and telecommunications. These prefixes are sometimes called prefix multipliers and are also used in electronics and physics. Each multiplier consists of a one-letter abbreviation and the prefix it represents.

In communications, electronics, and physics, multipliers are defined
in powers of ten from 10 ^{-24} to 10 ^{24} in
increments of three orders of magnitude - 10 ^{3} or 1,000. In
IT and data storage, multipliers are defined in powers of two from 2 ^{10} to
2 ^{80}, in increments of 10 orders of magnitude - 2 ^{10} or
1,024.

Examples of quantities or phenomena where powers of ten multipliers
are applied are frequency—including computer clock speeds—physical mass,
power, energy, voltage, and current. Multipliers to a power of 10 are
also used to define binary data speeds. For example, 1 kilobit per
second (kbps) equals 10 ^{3} or 1,000 bits per second
(bps); 1 megabit per second (Mbps) equals 10 ^{6} or 1,000,000
bps. The lowercase k is the technically correct symbol for kilo when
standing for 10 ^{3}, although the capital K is commonly used.

When binary data is stored in memory or on a fixed medium such as a
hard disk or drive, magnetic tape, or CD-ROM, power-of- two
multipliers are used. Technically, the capital K should be used for kilo
when it stands for 2 ^{10}. Therefore, 1 kilobyte (KB or KByte)
equals 2 ^{10} or 1,024 bytes; 1 megabyte (MB or MByte) equals
2 ^{20} or 1,048,576 bytes.

The choice of multipliers in powers of 10 or powers of 2 may appear random. It is helpful to remember that multiples of bits are almost always expressed in powers of 10, while multiples of bytes are usually expressed in powers of two. Data speed is rarely expressed in bytes per second, and data storage or storage is rarely expressed in bits.

The prefix kilo (1,000) was first introduced between 1865 and 1870. Although nowadays "mega" means "extremely good, big or successful", the scientific meaning is 1 million.

Giga comes from the Greek word for giant, and the term is said to have first been used at the 1947 conference of the International Union of Pure and Applied Chemistry. Tera (1 trillion) comes from the Greek word teras or teratos, meaning "wonder or monster," and has been in use since about 1947.

The prefixes exa (1 quintillion) and peta (1 quadrillion) were added to the International System of Units (SI) in 1975. However, the origin and history of the Peta with the measurement data is unclear. Zetta (1 sextillion) was added to SI metric prefixes in 1991.

When the prefixes are added to the term byte, they create units of measure ranging from 1,000 bytes (kilobytes) to 1 sextillion bytes (zettabytes) of data storage capacity. According to the IBM Dictionary of Computing, one megabyte corresponds to 1 million bytes of data storage capacity.

A gigabyte (GB or GByte) is approximately 1 billion bytes. There are two standards for measuring the number of bytes in a gigabyte: base-10 and base-2. Base-10 uses the decimal system to show that 1 GB is the 10th power of bytes, or 1 billion bytes. This is the standard used by most data storage manufacturers and consumers today. Computers typically use the base-2 or binary form of measurement. Base 2 is 1 GB, which is 1,073,741,824 bytes. The discrepancy between base 10 and base 2 measurements became more apparent as manufacturers began to produce larger capacity data storage media.

A terabyte (TB or TByte) is approximately 1 trillion bytes or 1,024 GB. A petabyte (PB or PByte) is two to the power of 50 bytes. A PB contains 1,024 TB, and approximately 1,024 PB equals 1 exabyte (EB or EByte). A zettabyte is approximately 1,000 EB or 1 billion TB.

When it comes to quantifying how much data storage capacity is offered in kilobytes, megabytes, etc., consider the table below.

Futurist Raymond Kurzweil, in his book The Singularity is Near, estimated the capacity of a human's functional memory at 1.25 TB. That means 800 people's memories fit into 1 PB of storage space.

If average MP3 encoding is about 1 MB per second (MBps) and an average song lasts about four minutes, then a petabyte of songs could play continuously for more than 2,000 years. If the average smartphone camera photo is 3MB and the average printed photo is 8.5 inches wide, a petabyte of side-by-side photos would be more than 48,000 miles long. That's almost long enough to wrap around the equator twice. According to Wes Biggs, CTO at Adfonic, 1 PB can store the DNA of the entire population of the United States and then clone it twice.

If you counted all the bits in 1 PB of storage at a rate of 1 bps, it would take 285 million years, according to data analysts at Deloitte Analytics. A bit is a binary digit, either a 0 or a 1; a byte is eight binary digits long. If you counted 1 bps, it would take 35.7 million years.

The future of data storage could be the yottabyte. It is a measure of storage capacity, roughly equal to 1,000 zettabytes, 1 trillion terabytes, one million trillion megabytes, or 1 septillion byte.

Written in decimal form, a yottabyte looks like this: 1,208,925,819,614,629,174,706,176. The prefix yotta is based on the Greek letter iota. According to Paul McFedries' book Word Spy, it would take 86 trillion years to download a 1 yottabyte file; for comparison, the entire content of the Library of Congress would only be 10 TB.

According to a 2010 Gizmodo article, storing a yottabyte of data on terabyte-sized disk drives would require 1 billion block-sized city data centers, which is a combination of the states of Rhode Island and Delaware. By the end of 2016, the storage density had increased to the point where one yottabyte could be stored on SDX cards, which correspond to around 800,000 cubic meters (approx. 11,834 large shipping containers).

Learn everything about Kibi, Mebi, Gibi, Tebi, Pebi in the video (English); the relatively new prefixes meant to express the power of two.

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