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 ► KB ► Computer Tech ► Software
From the May 2008 Issue of Prestwood eMag
 Tech Software:bit, kilobit, Byte, PetaByte: What's what?
Posted 12 years ago on 4/1/2008
Take Away: From bit to exabyte, know your quantities.

#### KB100978

Confused by megabit versus megabyte versus a Terabyte? These are actually pretty easy to understand if you break them down into units and prefixes. The units are bit and byte. The prefixes we'll focus on or kilo, mega, giga, tera, peta, and exa.

### Bit and Byte

Bit (lowercase "b")
A binary digit, a single, basic unit of information, used in connection with computers and information theory.  A bit is usually represented by a 0 or 1 but can also be represented by anything that can represent on and off. For example, the divits in the surface of a CD.

Byte (uppercase "B")
Adjacent bits, usually eight, processed by a computer as a unit. The combination of bits used to represent a particular letter, number, or special character. Early in computer science history (in the 1950s), computers used 3 and 6 bit bytes. The standard 8-bit byte standardized starting in the late 50s.

### Common Units Table

Now that you understand the fundamentals, the following table will make better sense to you.

 Unit Abbrev. In Bits Formal Informal Notes Bit b 1 N/A A binary digit, a single, basic unit of information, used in connection with computers and information theory.  A bit is usually represented by a 0 or 1 but can also be represented by anything that can represent on and off. For example, the divits in the surface of a CD. kilobit kb 1000 x 1 megabit mb Byte B 8 x 1 bit 1 Adjacent bits, usually eight, processed by a computer as a unit. The combination of bits used to represent a particular letter, number, or special character. KiloByte KB 210 x 8 bits 1,024 bytes 1,000 bytes Sometimes used loosely and imprecisely as 1000 bytes. Megabyte MB 220 x 8 bits 1,024 kilobytes. 1,000 kilobytes Sometimes used loosely and imprecisely as 1 million bytes. In computer science and industry usage, the prefix mega- often does not have its standard scientific meaning of 1,000,000, but refers instead to the power of two closest to 1,000,000, which is 220, or 1,048,576. Gigabyte GB 230 x 8 bits 1,024 megabytes. 1,000 megabytes Also known as 1,000 Megabytes. Sometimes used loosely and imprecisely as 1 billion bytes. Roughly the amount of data required to encode a human gene sequence (including all the redundant codons). Terabyte TB 240 x 8 bits 1,024 gigabytes. 1,000 gigabytes Also known as 1,000 Gigabytes. Sometimes used loosely and imprecisely as 1 trillion bytes. Petabyte PB 250 x 8 bits 1,024 Terabytes 1,000 petabytes Also known as 1,000 Terabytes. Sometimes used loosely and imprecisely as 1 quadrillion bytes. Exabyte EB 260 x 8 bits 1,024 petabytes 1,000 petabytes

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