DOUBLE

DOUBLE variables are 64-bits floating point numerical values up to sixteen digits precision (see IEEE 754 Double precision).

Syntax

Explicit declaration: DIM variable AS DOUBLE 'AS type variant; DIM variable# 'type suffix variant (#)
Implicit for a specific letter range: DEFDBL D-E '(legacy variant) all variables beginning with D(d) or E(e); _DEFINE D-E AS DOUBLE 'new variant in QB64(PE)
Implicit without declaration: variable# 'simply always use the type suffix

Values can range up to 16 digits. Decimal point accuracy depends on whole value places taken.
The suffix # can also be placed after a literal numerical value to designate the value as DOUBLE.
Values may be given as real number (123.456) or scientific notation using D as exponent marker (1.23456D+2).
PRINT usually takes the shorter of both notations (depending on the value) to output the numbers. In alternative you may use PRINT USING to designate your desired output format.
Floating decimal point numerical values cannot be _UNSIGNED.
Values can be converted to 8-bytes STRING values using _MKD$ and back to numbers with _CVD.

Some useful constants are available since QB64-PE v4.0.0

_SIZE_OF_DOUBLE = 8 'in bytes
_DOUBLE_MIN# = -1.797693134862315D+308 'smallest normal number
_DOUBLE_MAX# = 1.797693134862315D+308 'largest normal number
_DOUBLE_MIN_FRAC# = 2.225073858507201D-308 'smallest normal number closest to zero