Double(double-precision floating-point) variables are stored as IEEE 64-bit
(8-byte) floating-point numbers ranging in value from -1.79769313486232E308 -4.94065645841247E-324 for negative values and from 4.94065645841247E-324 to 1.79769313486232E308 for positive values. The type-declaration character for Double is #.
CDbl Function, Data Type Summary, Deftype Statements, Single Data Type.