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Double Data Type (Visual Basic) 

Holds signed IEEE 64-bit (8-byte) double-precision floating-point numbers ranging in value from -1.79769313486231570E+308 through -4.94065645841246544E-324 for negative values and from 4.94065645841246544E-324 through 1.79769313486231570E+308 for positive values. Double-precision numbers store an approximation of a real number.

The Double data type provides the greatest and smallest possible magnitudes for a number.

The default value of Double is 0.

Programming Tips

  • Precision. When you work with floating-point numbers, keep in mind that they do not always have a precise representation in memory. This could lead to unexpected results from certain operations, such as value comparison and the Mod operator. For more information, see Troubleshooting Data Types.

  • Trailing Zeros. The floating-point data types do not have any internal representation of trailing 0 characters. For example, they do not distinguish between 4.2000 and 4.2. Consequently, trailing 0 characters do not appear when you display or print floating-point values.

  • Type Characters. Appending the literal type character R to a literal forces it to the Double data type. Appending the identifier type character # to any identifier forces it to Double.

  • Framework Type. The corresponding type in the .NET Framework is the System.Double structure.