double Double-precision floating-point number occupies 8 bytes in the machine and is described by 64-bit binary.
Floating-point numbers are represented in the machine with an exponential type, and are broken down into four parts: number sign, mantissa, exponent sign, and exponent.
The number sign occupies 1 bit binary, which indicates the sign of the number.
The exponent sign is a 1-bit binary, indicating the sign of the exponent.
The mantissa represents a floating-point number with significant digits, 0.xxxxxxx, but no leading zeros and dots are stored.
Significant figures of the index deposit index.
How many digits the exponent occupies and how many digits the mantissa occupies is determined by the computer system.
It could be 24 digits plus mantissa, 8 digits plus exponent-float.
The number symbol plus the mantissa occupies 48 bits, and the index symbol plus the exponent occupies 16 bits-double.
Knowing the placeholders of these four parts, the size range is estimated in binary, and then converted to decimal, which is the numerical range you want to know.