Stored bits — click any bit to toggle it64 bits · big-endian, sign first
Sign — 1 bit. 0 = positive, 1 = negative.
Exponent — 11 bits. Scales the value by a power of two (bias-encoded).
Mantissa — 52 bits. The fraction after an implied leading 1.
Decoded valuenormal
0.1
17 significant digits: 0.10000000000000001
Sign (s)
0 → +
Exponent
raw 1019 − 1023 bias = −4
Mantissa (1.f)
1.6
Reconstructed from the bits
Nearest representable doubles (the gap around this value)
prev (bits − 1)—
current—
next (bits + 1)—
The famous demo
Each row shows the value JavaScript prints, its 17-digit truth, and the actual
64 bits. Watch how the bits of 0.1 + 0.2 differ from the bits of
0.3 by exactly one position.