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→top: follow up to page move – Denormal number → Subnormal number |
Add largest and smallest values to table, for explicitness, and update to use Maths Equations for visual formatting. |
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In [[computing]], a '''normal number''' is a non-zero number in a [[floating point|floating-point representation]] which is within the balanced range supported by a given floating-point format: it is a floating point number that can be represented without leading zeros in its [[significand]].
The magnitude of the '''smallest normal number''' in a format is given by
<math display="block">b^{\text{emin}}</math>
Similarly, the magnitude of the largest normal number in a format is given by ▼
where ''b'' is the base (radix) of the format (like common values 2 or 10, for binary and decimal number systems), and ''emin'' depends on the size and layout of the format.
▲Similarly, the magnitude of the '''largest normal number''' in a format is given by
:<math display="block">b^{\text{emax}}\cdot\left(b - b^{1-p}\right)</math>
where ''p'' is the precision of the format in [[numerical digit|digit]]s and ''emax'' is (−''emin'')+1.
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}}</ref>
{| class="wikitable" | style="text-align: right;"
|+Smallest and Largest Normal Numbers for common numerical Formats
!Format!!b!!p!!emin!!emax
!Smallest Normal Number
!Largest Normal Number
|-
|binary16||2||11||−14||15
|<math>2^{-14} \equiv 0.00006103515625</math>
|<math>2^{15}\cdot\left(2 - 2^{1-11}\right) \equiv 65504</math>
|-
|binary32||2||24||−126||127
|<math>2^{-126} \equiv \frac{1}{2^{126}}</math>
|<math>2^{127}\cdot\left(2 - 2^{1-24}\right)</math>
|-
|binary64||2||53||−1022||1023
|<math>2^{-1022} \equiv \frac{1}{2^{1022}}</math>
|<math>2^{1023}\cdot\left(2 - 2^{1-53}\right)</math>
|-
|binary128||2||113||−16382||16383
|<math>2^{-16382} \equiv \frac{1}{2^{16382}}</math>
|<math>2^{16383}\cdot\left(2 - 2^{1-113}\right)</math>
|-
|decimal32||10||7||−95||96
|<math>10^{-95} \equiv \frac{1}{10^{95}}
</math>
|<math>10^{96}\cdot\left(10 - 10^{1-7}\right) \equiv 9.999999 \cdot 10^{96}</math>
|-
|decimal64||10||16||−383||384
|<math>10^{-383} \equiv \frac{1}{10^{383}}
</math>
|<math>10^{384}\cdot\left(10 - 10^{1-16}\right)</math>
|-
|decimal128||10||34||−6143||6144
|<math>10^{-6143} \equiv \frac{1}{10^{6143}}
</math>
|<math>10^{6144}\cdot\left(10 - 10^{1-34}\right)</math>
|}
For example, in the smallest decimal format in the table (decimal32), the range of positive normal numbers is 10<sup>−95</sup> through 9.999999 × 10<sup>96</sup>.
Non-zero numbers smaller in magnitude than the smallest normal number are called [[subnormal number|'''subnormal''']] '''numbers''' (or ''denormal numbers'').
== See also ==
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