From QB64.org wiki
_FLOAT numerical values offer the maximum floating-point decimal precision available using QB64.
- DIM variable AS _FLOAT
- QB64 always allocates 32 bytes to store this value.
- It is safe to assume this value is at least as precise as DOUBLE.
- Under the current implementation it is stored in a 10-byte floating point variable.
- _FLOAT variables can also use the ## variable name type suffix.
- Values returned may be expressed using exponential or scientific notation using E for SINGLE or D for DOUBLE precision.
- According to IEEE-754 this can store a value of up to 1.1897E+4932 compared to a DOUBLE which goes up to 1.7976E+308.
- Floating decimal point numerical values cannot be _UNSIGNED.
- Values can be converted to 32 byte ASCII strings using _MK$ and back with _CV.
- When a variable has not been assigned or has no type suffix, the value defaults to SINGLE.
- Note: OpenGL's _GL_FLOAT constant is a SINGLE (4 byte) floating point number, while a native QB64 _FLOAT is a 10-byte floating point number.