Maximus Maximus - 1 year ago 87
Javascript Question

What's the bit pattern for minimal value in double 64 bit

I assumed that the minimal positive value that can be put into double floating point is this

0 0000000000 00000000000000000000000000000000000000000000000000000

And in scientific form it's this:

1 x 2^{-1023}

However, this article states that:

As mentioned above, zero is not directly representable in the straight
format, due to the assumption of a leading 1 (we'd need to specify a
true zero mantissa to yield a value of zero). Zero is a special value
denoted with an exponent field of all zero bits, and a fraction field
of all zero bits.

So what's the pattern for minival positive value?

Answer Source

When the exponent part is all zero, the numbers are subnormals or denormals, where the implicit digit is 0 instead of 1 (the exponent is the same as the smallest normal float). Therefore

0 00000000000 0000000000000000000000000000000000000000000000000000

is zero, and the next number

0 00000000000 0000000000000000000000000000000000000000000000000001

is the smallest positive number, being equal to

0.00000000000000000000000000000000000000000000000000012×2-1022 = 2-1074 ≈ 5.0×10-324

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