Access Database Design and Programming, Second Edition

Variables and Data Types

A variable can be thought of as a memory location that can hold values of a specific type. The value in a variable may change during the life of the program—hence the name variable.

In VBA, each variable has a specific data type , which indicates which type of data it may hold. For instance, a variable that holds text strings has a String data type and is called a string variable. A variable that holds integers (whole numbers) has an Integer data type and is called an integer variable. For reference, Table 10.1 shows the complete set of VBA data types, along with the amount of memory that they consume and their range of values. We will discuss a few of the more commonly used data types in a moment.

Table 10-1. VBA Data Types

Type	Size in Memory	Range of Values
Byte	1 byte	0 to 255
Boolean	2 bytes	True or False
Integer	2 bytes	–32,768 to 32,767
Long (long integer)	4 bytes	–2,147,483,648 to 2,147,483,647
Single (single-precision real)	4 bytes	Approximately –3.4E38 to 3.4E38
Double (double-precision real)	8 bytes	Approximately –1.8E308 to 4.9E324
Currency (scaled integer)	8 bytes	Approximately –922,337,203,685,477.5808 to 922,337,203,685,477.5807
Date	8 bytes	1/1/100 to 12/31/9999
Object	4 bytes	Any Object reference
String	Variable length: 10 bytes + string length; Fixed length: string length	Variable length: <= about 2 billion (65,400 for Win 3.1) Fixed length: up to 65,400
Variant	16 bytes for numbers 22 bytes + string length ...