| The only data that computers understand is on and off. This data is referred to as a “bit” (binary digit). Computers can tell if it’s on or off depending on the bit. Each bit has an electric gate or switch. 1 refers to being open or on and 2 refers to being closed or off. So if the electricity can get through then it is open or 1 and if the electricity is blocked/cannot get through then the it is closed or 0. | | Bits can be grouped together to allow more complex data. Eight bits of data grouped together form a “byte”. This creates 256 different combinations of 1/0. | | | Note: The abbreviation for bit is a lowercase “b”; the abbreviation for byte is an uppercase “B”. | | Computer data is normally measured in binary code which is expressed in exponents of two. The prefix for multiples is based on the metric system. | | The nearest binary number to 1,000 is 2^10, or 1,024; 1024 bytes became known as the “kilobyte”. A binary kilo equals 1024 and a kilo based off the metric system equals 1000. So (one kilobyte = 1024 bytes) and (one kilogram = 1,000 grams) just so you’re not confused… or are you? Hah. | | The International Electrotechnical Commission (IEC) changed the IEC International Standard in 1998. Instead of using the metric prefixes for multiples in binary code, the new IEC standard invented specific prefixes for binary multiples made up of only the first two letters of the metric prefixes and adding the first two letters of the word “binary”. So instead of Kilobyte (KB) or Gigabyte (GB), it would be kibibyte (KiB) or gibibyte (GiB). | |
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| Old Standard | | bit |
b | 0 or 1 | | byte |
B | 8 bits | | kilobit |
kb | 1000 bits | | Kilobyte (binary) |
KB | 1024 bytes | | Kilobyte (decimal) |
KB | 1000 bytes | | Megabit |
Mb | 1000 kilobits | | Megabyte (binary) |
MB | 1024 Kilobytes | | Megabyte (decimal) |
MB | 1000 Kilobytes | | Gigabit |
Gb | 1000 Megabits | | Gigabyte (binary) |
GB | 1024 Megabytes | | Gigabyte (decimal) |
GB | 1000 Megabytes | | Terabit |
Tb | 1000 Gigabits | | Terabyte (binary) |
TB | 1024 Gigabytes | | Terabyte (decimal) |
TB | 1000 Gigabytes | | Petabit |
Pb | 1000 Terabits | | Petabyte (binary) |
PB | 1024 Terabytes | | Petabyte (decimal) |
PB | 1000 Terabytes | | Exabit |
Eb | 1000 Petabits | | Exabyte (binary) |
EB | 1024 Petabytes | | Exabyte (decimal) |
EB | 1000 Petabytes |
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| IEC Standard | | bit |
bit | 0 or 1 | | byte |
B | 8 bits | | kibibit |
Kibit | 1024 bits | | kilobit |
kbit | 1000 bits | | kibibyte (binary) |
KiB | 1024 bytes | | kilobyte (decimal) |
kB | 1000 bytes | | megabit |
Mbit | 1000 kilobits | | mebibyte (binary) |
MiB | 1024 kibibytes | | megabyte (decimal) |
MB | 1000 kilobytes | | gigabit |
Gbit | 1000 megabits | | gibibyte (binary) |
GiB | 1024 mebibytes | | gigabyte (decimal) |
GB | 1000 megabytes | | terabit |
Tbit | 1000 gigabits | | tebibyte (binary) |
TiB | 1024 gibibytes | | terabyte (decimal) |
TB | 1000 gigabytes | | petabit |
Pbit | 1000 terabits | | pebibyte (binary) |
PiB | 1024 tebibytes | | petabyte (decimal) |
PB | 1000 terabytes | | exabit |
Ebit | 1000 petabits | | exbibyte (binary) |
EiB | 1024 pebibytes | | exabyte (decimal) |
EB | 1000 petabytes |
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When used to describe Memory Size, or Data Storage, bits/bytes are generally
calculated as some exponent of two: |
|
Old Standard | | 1 | bit | (b) | | | 1 | byte | (B) | = 8 bits | | 1 | Kilobyte | (K / KB) | = 2^10 bytes = 1,024
bytes | | 1 | Megabyte | (M / MB) | = 2^20 bytes = 1,048,576 bytes | | 1 | Gigabyte | (G / GB) | = 2^30 bytes =
1,073,741,824 bytes | | 1 | Terabyte | (T / TB) | = 2^40 bytes =
1,099,511,627,776 bytes | | 1 | Petabyte | (P / PB) | = 2^50 bytes =
1,125,899,906,842,624 bytes | | 1 | Exabyte | (E / EB) | = 2^60 bytes =
1,152,921,504,606.846,976 bytes | | 1 | Zettabyte | (Z / ZB) | = 2^70 bytes =
1,180,591,620,717,411,303,424 bytes | | 1 | Yottabyte | (Y / YB) | = 2^80 bytes =
1,208,925,819,614,629,174,706,176 bytes |
| | Note: In the metric system the “k” or “kilo” prefix is always lowercase but since these binary uses are not properly metric, it has become standard to use an uppercase “K” for the binary form. |
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IEC Standard | | 1 | bit | (bit) | | | 1 | byte | (B) | = 8 bits | | 1 | kibibyte | (KiB) | = 2^10 bytes = 1,024 bytes | | 1 | mebibyte | (MiB) | = 2^20 bytes = 1,048,576 bytes | | 1 | gibibyte | (GiB) | = 2^30 bytes = 1,073,741,824
bytes | | 1 | tebibyte | (TiB) | = 2^40 bytes = 1,099,511,627,776
bytes | | 1 | pebibyte | (PiB) | = 2^50 bytes =
1,125,899,906,842,624 bytes | | 1 | exbibyte | (EiB) | = 2^60 bytes =
1,152,921,504,606.846,976 bytes | | 1 | zebibyte | (ZiB) | = 2^70 bytes =
1,180,591,620,717,411,303,424 bytes | | 1 | yobibyte | (YiB) | = 2^80 bytes =
1,208,925,819,614,629,174,706,176 bytes |
| | Note: For consistency with the other prefixes for binary multiples, the initial “K” used in the abbreviation for kibibyte (2^10) has been capitalized. |
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Decimal System Although data storage capacity is generally expressed in binary code, many hard
drive manufacturers (and some newer BIOSs) use a decimal system to express
capacity: |
|
Old Standard | | 1 | bit | (b) | | | 1 | byte | (B) | = 8 bits
| | 1 | Kilobyte | (K / KB) | = 10^3 bytes = 1,000 bytes
| | 1 | Megabyte | (M / MB) | = 10^6 bytes = 1,000,000 bytes
| | 1 | Gigabyte | (G / GB) | = 10^9 bytes = 1,000,000,000 bytes
| | 1 | Terabyte | (T / TB) | = 10^12 bytes = 1,000,000,000,000
bytes | | 1 | Petabyte | (P / PB) | = 10^15 bytes = 1,000,000,000,000,000
bytes | | 1 | Exabyte | (E / EB) | = 10^18 bytes =
1,000,000,000,000,000,000 bytes | | 1 | Zettabyte | (Z / ZB) | = 10^21 bytes =
1,000,000,000,000,000,000,000 bytes | | 1 | Yottabyte | (Y / YB) | = 10^24 bytes =
1,000,000,000,000,000,000,000,000 bytes |
| | Note: A third definition of Megabyte is that used in formatting floppy disks: 1 Megabyte = 1,024,000 bytes. |
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IEC Standard | | 1 | bit | (bit) | | | 1 | byte
| (B)
| = 8 bits
| | 1 | kilobyte
| (kB) | = 10^3 bytes = 1,000 bytes | | 1 | megabyte | (MB) | = 10^6 bytes =
1,000,000 bytes
| | 1 | gigabyte | (GB) | = 10^9 bytes = 1,000,000,000 bytes | | 1 | terabyte | (TB) | = 10^12 bytes = 1,000,000,000,000 bytes | | 1 | petabyte | (PB)
| = 10^15 bytes = 1,000,000,000,000,000 bytes | | 1 | exabyte | (EB) | = 10^18 bytes = 1,000,000,000,000,000,000 bytes | | 1 | zettabyte | (ZB) | = 10^21 bytes = 1,000,,000,000,000,000,000,000
bytes | | 1 | yottabyte | (YB) | = 10^24 bytes =
1,000,000,000,000,000,000,000,000 bytes |
| | Note: Note the use of a lowercase “k” in the abbreviation for kilobyte, in keeping with the metric system. |
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| When used to describe Data Transfer Rate, bits/bytes are calculated as in the metric system: |
Old Standard | | 1 | bit | (b) | = 0 or 1 = one binary digit | | 1 | kilobit | (kb / Kb / K) | = 10^3 bits = 1,000 bits | | 1 | Megabit | (Mb) | = 10^6 bits = 1,000,000 bits | | 1 | Gigabit | (Gb) | = 10^9 bits = 1,000,000,000 bits | | 1 | Terabit | (Tb) | = 10^12 bits = 1,000,000,000,000
bits | | 1 | Petabit | (Pb) | = 10^15 bits =
1,000,000,000,000,000 bits | | 1 | Exabit | (Eb) | = 10^18 bits =
1,000,000,000,000,000,000 bits | | 1 | Zettabit | (Zb) | = 10^21 bits =
1,000,000,000,000,000,000,000 bits | | 1 | Yottabit | (Yb) | = 10^24 bits =
1,000,000,000,000,000,000,000,000 bits |
| | Note: Kilobits per second is usually shortened to kbps or Kbps. Although technically speaking, the term kilobit should have a lowercase initial letter, it has become common to capitalize it in abbreviation (e.g. “56 Kbps” or “56K”). The simple “K” might seem ambiguous but, in the context of data transfer, it can be assumed that the measurement is in bits rather than bytes unless indicated otherwise. |
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IEC Standard | | 1 | bit | (bit) | = 0 or 1 = one binary digit | | 1 | kilobit | (kbit) | = 10^3 bits = 1,000 bits | | 1 | megabit | (Mbit) | = 10^6 bits = 1,000,000 bits | | 1 | gigabit | (Gbit) | = 10^9 bits = 1,000,000,000 bits | | 1 | terabit | (Tbit) | = 10^12 bits = 1,000,000,000,000
bits | | 1 | petabit | (Pbit) | = 10^15 bits =
1,000,000,000,000,000 bits | | 1 | exabit | (Ebit) | = 10^18 bits =
1,000,000,000,000,000,000 bits | | 1 | zettabit | (Zbit) | = 10^21 bits =
1,000,000,000,000,000,000,000 bits | | 1 | yottabit | (Ybit) | = 10^24 bits =
1,000,000,000,000,000,000,000,000 bits |
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