Decimal Data Type (Visual Basic)
Holds signed 128-bit (16-byte) values representing 96-bit (12-byte) integer numbers scaled by a variable power of 10. The scaling factor specifies the number of digits to the right of the decimal point; it ranges from 0 through 28. With a scale of 0 (no decimal places), the largest possible value is +/-79,228,162,514,264,337,593,543,950,335 (+/-7.9228162514264337593543950335E+28). With 28 decimal places, the largest value is +/-7.9228162514264337593543950335, and the smallest nonzero value is +/-0.0000000000000000000000000001 (+/-1E-28).
The Decimal data type provides the greatest number of significant digits for a number. It supports up to 29 significant digits and can represent values in excess of 7.9228 x 10^28. It is particularly suitable for calculations, such as financial, that require a large number of digits but cannot tolerate rounding errors.
The default value of Decimal is 0.
Precision. Decimal is not a floating-point data type. The Decimal structure holds a binary integer value, together with a sign bit and an integer scaling factor that specifies what portion of the value is a decimal fraction. Because of this, Decimal numbers have a more precise representation in memory than floating-point types (Single and Double).
Performance. The Decimal data type is the slowest of all the numeric types. You should weigh the importance of precision against performance before choosing a data type.
Widening. The Decimal data type widens to Single or Double. This means you can convert Decimal to either of these types without encountering a System.OverflowException error.
Trailing Zeros. Visual Basic does not store trailing zeros in a Decimal literal. However, a Decimal variable preserves any trailing zeros acquired computationally. The following example illustrates this.
Dim d1, d2, d3, d4 As Decimal d1 = 2.375D d2 = 1.625D d3 = d1 + d2 d4 = 4.000D MsgBox("d1 = " & CStr(d1) & ", d2 = " & CStr(d2) _ & ", d3 = " & CStr(d3) & ", d4 = " & CStr(d4))
The output of MsgBox in the preceding example is as follows:
d1 = 2.375, d2 = 1.625, d3 = 4.000, d4 = 4
Type Characters. Appending the literal type character D to a literal forces it to the Decimal data type. Appending the identifier type character @ to any identifier forces it to Decimal.
Framework Type. The corresponding type in the .NET Framework is the System.Decimal structure.
You might need to use the D type character to assign a large value to a Decimal variable or constant. The following example illustrates this.
Dim bigDec1 As Decimal = 9223372036854775807 ' No overflow. Dim bigDec2 As Decimal = 9223372036854775808 ' Overflow. Dim bigDec3 As Decimal = 9223372036854775808D ' No overflow.
The compiler interprets a literal as Long unless it is followed by a literal type character. The declaration for bigDec1 does not produce an overflow because its value is within the range for Long. However, the value for bigDec2 is too large for Long, so the compiler generates an error. The literal type character D solves the problem for bigDec3 by forcing the compiler to interpret the literal as Decimal.