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Double precision

In computing, double precision is a computer numbering format that occupies two storage locations in computer memory at address and address+1. A double precision number, sometimes simply a double, may be defined to be an integer, fixed point, or floating point.

Modern computers with 32-bit stores (single precision) provide 64-bit double precision. Double precision floating point is an IEEE 754 standard for encoding floating point numbers that uses 8 bytes.

Double precision memory format

The format is written with an implicit integer bit with value 1 unless the written exponent is all zeros. Thus only 52 bits of the fraction appear in the memory format.

Exponent encodings

The true exponent = written exponent - exponent bias

All bit patterns are valid encodings.

Double precision examples

(1/3 rounds down instead of up like single precision, because of the odd number of bits in the significand.)

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In baseball, a double is a two-base hit. See double (baseball).