Visual Basic Data Types

Visual Basic and Visual Basic for Applications support the following data types: Boolean

Indicates the presence of logical data that can contain either of two values, True or False. The keywords True and False are constants that are predefined in VBA, so you can make use of them in your code when you want to assign a value to a Boolean variable, as the following code fragment shows:

varl = True var2 = False

Many of the properties of ActiveX controls have possible values of True or False. In addition, within programs, Boolean variables often serve as flags to control program flow, as the following example, which toggles (or reverses) the value of myBool within the If...Else...End If construct, shows:

If myBool = False Then myVar = 4 myBool = True Else myVar = 5 myBool = False End If

Storage required Two bytes

Range

True or False

Default value False

Byte

The smallest numeric subtype available in VBA. Because only one byte holds a number ranging from 0 to 255 (or 00 to FF in hexadecimal), there is no room for the sign, and so only positive numbers can be held in a Byte data type. Attempting to assign a negative number or a number greater than 255 to byte data results in a runtime error.

Storage required One byte

Range

0 to 255

Default value 0

Currency

Provides a special numeric format for storing monetary values.

Storage required Eight bytes

Range

-922,337,203,685,477.5808 to 922,337,203,685,477.5807

Default value 0

Date

Contains a specially formatted number that represents the date or time.

Storage Required Eight bytes

Range

1 January 100 to 31 December 9999

Default value 00:00:00

Decimal

A variant subtype (and not a separate data type) that contains decimal numbers scaled by a power of 10. Variants of subtype Decimal can only be created by the CDec conversion function.

Storage required 14 bytes

Range

With no decimal point:

Visual Basic Data Types 27

With up to 28 decimal places: +/- 7.9228162514264337593543950335

Default value 0

Double

Stores a double precision floating point number; basically, it's the industrial strength version of the Single data type.

Storage required Eight bytes

Range

Negative values: -1.79769313486232E308 to -4.94065645841247E-324

Positive values: 1.79769313486232E308 to 4.94065645841247E-324

Default value 0

Integer

A whole number that ranges from -32,768 to 32,767. One bit represents the sign (either positive or negative). Attempting to assign a value outside its range results in a runtime error.

Storage required two bytes

Range

-32,768 to 32,767

Default value 0

Long

A signed integer stored in four bytes of memory. One bit represents the sign.

Storage required Four bytes

Range

-2,147,483,648 to 2,147,486,647

Default value 0

Object

Contains a reference to (i.e., the address of) an object. The object can be an OLE automation object such as an ActiveX component, or it can be a class object within your project. When you use the generic Object data type, rather than a more specific object type, you automatically use late binding. For more information about using the Object data type, see Chapter 4, Class Modules.

Storage required Four bytes

Range

Any object reference

28 Chapter 3 - VBA Variables and Data Types

Default value Nothing*

A single precision number that represents fractional numbers, numbers with decimal places, or exponential numbers.

Storage required Four bytes

Range

Negative values: -3.402823E38 to -1.401298E-45

Positive values: 1.401298E-45 to 3.402823E38

Default value 0

String (fixed length)

Popular in VB applications when memory and disk storage was at a premium and programmers had to spend most of their time optimizing the size of applications, fixed-length strings are now rarely used. To declare a fixed-length string, use the syntax:

Dim|Private|Public varname As String * stringlength

Storage required

Length of string

Range

1 to 65,400 characters

Default value

A number of spaces equal to the length of the string

String (variable length)

String data type that expands and contracts dynamically to store as many characters as required, up to somewhere in the neighborhood of two billion. To declare a variable-length string, simply use the String keyword: Dim variablename As String

VBA includes many useful intrinsic functions for handling and manipulating string data. The list of string functions has been expanded in VB6, as many of the string-manipulation functions introduced into VBScript have now made their way into the full language.

Storage required

10 + length of the string

Range

0 to 2 billion characters

Default value

Zero-length string ("")

* Nothing and Empty are special Variant data subtypes and do not have the same meaning. For more information, see the section about the Variant data type later in this chapter.

Visual Basic Data Types 29

User-defined type

A user-defined type allows you to create a single data type consisting of a combination of intrinsic VB data types, arrays, objects, or other user-defined types. User-defined types are created using the Type statement. The following snippet shows how to declare a user-defined type:

Type udtCustomer Name As String Code As Long Orders(20) As udtOrders RenewalDate As Date End Type

User-defined types are important data structures in VB and are often essential when interfacing with the Windows API. For more information on user-defined types, see the section "User-Defined Types" later in this chapter and the entry for the Type statement in Chapter 7, The Language Reference.

Storage required

Sum of storage size of the individual elements

Range

Same range as data type of individual elements

Default value

The default value of the individual elements

Variant (character)

The variant string subtype is very much like a variable-length string data type. All VB string functions can accept variant strings, and many have two versions that return either a strongly typed string data type or a variant string subtype. For example, the Left function—which returns the leftmost n characters of a string—has two variations, Left$ (which returns a string data type) and Left (which returns a variant of subtype string).

Storage required

22 bytes + length of string

Range

Same as variable length string

Default value Empty*

Variant (numeric)

The variant numeric subtype holds any numeric value. As with all variant data, memory allocation changes dynamically to accommodate the numeric value. The variant also includes a special Decimal subtype that doesn't have an intrinsic equivalent, and allows you to hold very large numbers in a variety of formats.

Storage required 16 bytes

* Nothing and Empty are special Variant data subtypes and don't have the same meaning. For more information, see the section about the Variant data type later in this chapter.

30 Chapter 3 - VBA Variables and Data Types

Range

Same as Double

Default Value Empty*

Was this article helpful?

0 -1

Post a comment