Numeric Data Types
Visual Basic supplies several numeric data types for handling numbers in various representations. Integral types represent only whole numbers (positive, negative, and zero), and nonintegral types represent numbers with both integer and fractional parts.
For a table showing a side-by-side comparison of the Visual Basic data types, see Data Type Summary (Visual Basic).
Integral Numeric Types
Integral data types are those that represent only numbers without fractional parts.
The signed integral data types are SByte Data Type (Visual Basic) (8-bit), Short Data Type (Visual Basic) (16-bit), Integer Data Type (Visual Basic) (32-bit), and Long Data Type (Visual Basic) (64-bit). If a variable always stores integers rather than fractional numbers, declare it as one of these types.
The unsigned integral types are Byte Data Type (Visual Basic) (8-bit), UShort Data Type (Visual Basic) (16-bit), UInteger Data Type (32-bit), and ULong Data Type (Visual Basic) (64-bit). If a variable contains binary data, or data of unknown nature, declare it as one of these types.
Performance
Arithmetic operations are faster with integral types than with other data types. They are fastest with the Integer and UInteger types in Visual Basic.
Large Integers
If you need to hold an integer larger than the Integer data type can hold, you can use the Long data type instead. Long variables can hold numbers from -9,223,372,036,854,775,808 through 9,223,372,036,854,775,807. Operations with Long are slightly slower than with Integer.
If you need even larger values, you can use the Decimal Data Type (Visual Basic). You can hold numbers from -79,228,162,514,264,337,593,543,950,335 through 79,228,162,514,264,337,593,543,950,335 in a Decimal variable if you do not use any decimal places. However, operations with Decimal numbers are considerably slower than with any other numeric data type.
Small Integers
If you do not need the full range of the Integer data type, you can use the Short data type, which can hold integers from -32,768 through 32,767. For the smallest integer range, the SByte data type holds integers from -128 through 127. If you have a very large number of variables that hold small integers, the common language runtime can sometimes store your Short and SByte variables more efficiently and save memory consumption. However, operations with Short and SByte are somewhat slower than with Integer.
Unsigned Integers
If you know that your variable never needs to hold a negative number, you can use the unsigned typesByte, UShort, UInteger, and ULong. Each of these data types can hold a positive integer twice as large as its corresponding signed type (SByte, Short, Integer, and Long). In terms of performance, each unsigned type is exactly as efficient as its corresponding signed type. In particular, UInteger shares with Integer the distinction of being the most efficient of all the elementary numeric data types.
Nonintegral Numeric Types
Nonintegral data types are those that represent numbers with both integer and fractional parts.
The nonintegral numeric data types are Decimal (128-bit fixed point), Single Data Type (Visual Basic) (32-bit floating point), and Double Data Type (Visual Basic) (64-bit floating point). They are all signed types. If a variable can contain a fraction, declare it as one of these types.
Decimal is not a floating-point data type. Decimal numbers have a binary integer value and an integer scaling factor that specifies what portion of the value is a decimal fraction.
Floating-point (Single and Double) numbers have larger ranges than Decimal numbers but can be subject to rounding errors. Floating-point types support fewer significant digits than Decimal but can represent values of greater magnitude.
Nonintegral number values can be expressed as mmmEeee, in which mmm is the mantissa (the significant digits) and eee is the exponent (a power of 10). The highest positive values of the nonintegral types are 7.9228162514264337593543950335E+28 for Decimal, 3.4028235E+38 for Single, and 1.79769313486231570E+308 for Double.
Performance
Double is the most efficient of the fractional data types, because the processors on current platforms perform floating-point operations in double precision. However, operations with Double are not as fast as with the integral types such as Integer.
Small Magnitudes
For numbers with the smallest possible magnitude (closest to 0), Double variables can hold numbers as small as -4.94065645841246544E-324 for negative values and 4.94065645841246544E-324 for positive values.
Small Fractional Numbers
If you do not need the full range of the Double data type, you can use the Single data type, which can hold floating-point numbers from -3.4028235E+38 through 3.4028235E+38. The smallest magnitudes for Single variables are -1.401298E-45 for negative values and 1.401298E-45 for positive values. If you have a very large number of variables that hold small floating-point numbers, the common language runtime can sometimes store your Single variables more efficiently and save memory consumption.
See Also
Tasks
How to: Hold Integers in a Variable
How to: Hold Fractions in a Variable
How to: Hold the Largest Possible Number in a Variable
How to: Optimize Storage of Positive Integers With Unsigned Types
How to: Call a Windows Function that Takes Unsigned Types
How to: Hold the Most Significant Digits in a Variable
How to: Hold Money Values in a Variable