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In computing, quad precision is a computer numbering format that occupies four storage locations in computer memory at address, address+1, address+2, and address+3. A quad-precision number, sometimes simply a quad, may be defined to be an integer, fixed point, or floating point.
Pedantic usage note: When using quad-precision as an adjective, as in quad-precision number, hyphenate it. When using it as a noun ("Double precision differs from quad precision."), do not hyphenate it.
In the IEEE 754r proposed revised floating point standard, this is the third basic binary floating
point format, together with 64 bits double precision and the 32 bit single precision formats.
Quad precision memory format
Sign bit: 1
Exponent width: 15
Significand precision: 113
The format is written with an implicit integer bit with value 1 unless the written exponent is all zeros. Thus only 112 bits of the fraction appear in the memory format.
syyy yyyy yyyy yyyy xxxx xxxx xxxx xxxx … xxxx xxxx (112 xs)
Exponent encodings
Emin (0x0001) = -16382
Emax (0x7ffe) = 16383
Exponent bias (0x3fff) = 16383
The true exponent = written exponent - exponent bias
0x0000 and 0x7fff are reserved exponents
0x0000 is used to represent zero and denormals
0x7fff is used to represent infinity and NaNs
All bit patterns are valid encodings.
Quad precision examples in hexadecimal
3fff 0000 0000 0000 0000 0000 0000 0000 = 1
c000 0000 0000 0000 0000 0000 0000 0000 = -2
7fef ffff ffff ffff ffff ffff ffff ffff ~ 2.37946299071446353017 x 104932 (Max Quad)
3ffe aaaa aaaa aaaa aaaa aaaa aaaa aaab ~ 1/3
(1/3 rounds up like double precision, because of the odd number of bits in the significand.)
0000 0000 0000 0000 0000 0000 0000 0000 = 0
8000 0000 0000 0000 0000 0000 0000 0000 = -0
7f80 0000 0000 0000 0000 0000 0000 0000 = Infinity
ff80 0000 0000 0000 0000 0000 0000 0000 = -Infinity
See also
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