How to Declare Variables and Data Types - VBA Tutorial

Declaring variables is an essential part of programming in VBA. Declaring properly will help you avoid errors and improve the overall quality of your code.

What Does Declaring a Variable Mean?

Declaring a variable in VBA (or any programming language) means to specify the name and data type of the variable, so that the compiler or interpreter knows how to allocate memory for the variable and how to interpret the data stored in it. For example, if you declare a variable called "name" as a string data type, the compiler or interpreter will know that the variable is used to store text data in a string, and it will allocate the appropriate amount of memory to hold the value of the variable. This is an important step in the development of any program, as it helps to ensure that the code is efficient, readable, and maintainable.

How to Declare a Variable in VBA

In VBA, you can declare a variable using the Dim (short for Dimension) keyword, followed by the name of the variable and its data type. For example, to declare a variable called "name" that is a string data type, you would use the following code:

Dim name As String

You can also declare multiple variables at the same time by separating them with commas, like this:

Dim name As String, age As Integer, date As Date

It is generally considered good practice to explicitly declare variables in VBA, as it can help avoid potential errors and improve the readability of your code. You can also specify the scope of a variable using the Private, Public, or Global keywords, depending on where you want the variable to be available within your code. For example:

Private Dim name As String

This would declare a variable called "name" that is only accessible within the current module or procedure.

Why Should You Declare Your Variables?

There are several reasons why you should declare a variable in a program, including:

To allocate the appropriate amount of memory for the variable, based on its data type. This ensures that the program has enough memory to store and manipulate the data stored in the variable.
To explicitly state the name and data type of the variable, which can make the code more readable and maintainable. This can help other people who are reading or working with your code to understand what the variable is used for and how it is intended to be used.
To avoid errors or bugs in your code. For example, if you try to use a variable that has not been declared, the compiler or interpreter may throw an error or warning, indicating that the variable does not exist.
To enforce good coding practices and standards. In some programming languages, such as VBA, explicitly declaring variables is required in order to use them in your code. This helps to ensure that variables are properly defined and used consistently throughout the program.

Do All Variables Need to be Declared?

It is generally considered good practice to explicitly declare all variables that you plan to use in your code. This can help to prevent accidental or unintentional use of undeclared variables, which can lead to errors or bugs in your code.

What is Option Explicit?

Option Explicit is a default setting in VBA (Visual Basic for Applications) that requires all variables to be declared before they can be used in the code. This means that if you want to use a variable in your VBA code, it must be declared:

Dim name As String

Enabling the Option Explicit setting can help to prevent errors or bugs in your code, as it ensures that all variables are properly defined and used consistently throughout the program. It also makes the code more readable and maintainable, as it explicitly states the name and data type of each variable.

How to use Option Explicit in VBA to help declaring variables

To enable the Option Explicit setting in VBA, you can add the following line at the top of your code module:

Option Explicit

This will tell the compiler or interpreter to check for undeclared variables and throw an error if it encounters any. By default, the Option Explicit setting is enabled in VBA, so you only need to add this line if you have disabled it in your code.

Data Types

Data types are used to define the kind of information that a variable can store, as well as the operations that can be performed on it. VBA has a set of built-in data types, which are used to represent different kinds of data and determine how it is stored and manipulated within the program.

While it is good practice to declare every variable with a relevant data type, if a data type is not explicitly declared, it will default as a variant.

Numeric Data Types

List of all Numeric VBA data types, the related storage size, and the value range

Byte - Used to store small, positive whole numbers (numbers without decimal points). It can store numbers from 0 to 255

Integer - Used to store whole numbers (numbers without decimal points)

Long - Similar to the Integer data type, but it can store larger numbers

Single - Used to store numbers with decimal points

Currency - Used to store numbers that represent currency values. It is similar to the Decimal data type, but it has a fixed number of decimal places (four) and it is optimized for financial calculations

Double - Similar to the Single data type, but it can store larger numbers with decimal points

Decimal - Used to store numbers with decimal points. It is similar to the Single and Double data types, but it has a higher precision and a smaller range.

Non-Numeric Data Types

Fixed-length String - Used to store text values of a fixed length. When you declare a variable with a fixed-length String data type, you must specify the length of the string, and the variable will always be that length, even if the string it contains is shorter

Variable-length String - Used to store text values of a variable length. When you declare a variable with a variable-length String data type, you do not need to specify the length of the string, and the variable will automatically adjust its length to fit the string it contains

Boolean - Used to store values that can only be either True or False

Date - This data type is used to store date and time values

Variant - This data type can store any type of data, including numbers, text, and objects

Object - Object data type is used to store objects, which are instances of classes. An object can contain data and code that can be used to manipulate that data

Numeric Variant - This data type is a special type of Variant data type that can only store numeric values (including numbers with decimal points and numbers in exponential notation)

Variant Text - This data type is a special type of Variant data type that can only store text values