double (C# Reference)
The double keyword signifies a simple type that stores 64-bit floating-point values. The following table shows the precision and approximate range for the double type.
.NET Framework type
±5.0 × 10−324 to ±1.7 × 10308
By default, a real numeric literal on the right side of the assignment operator is treated as double. However, if you want an integer number to be treated as double, use the suffix d or D, for example:
double x = 3D;
You can mix numeric integral types and floating-point types in an expression. In this case, the integral types are converted to floating-point types. The evaluation of the expression is performed according to the following rules:
If one of the floating-point types is double, the expression evaluates to double, or bool in relational or Boolean expressions.
A floating-point expression can contain the following sets of values:
Positive and negative zero.
Positive and negative infinity.
Not-a-Number value (NaN).
The finite set of nonzero values.
For more information about these values, see IEEE Standard for Binary Floating-Point Arithmetic, available on the IEEE Web site.
For more information, see the following sections in the C# Language Specification:
1.3 Types and Variables
4.1.5 Integral Types