OpenOffice.org BASIC Guide - OpenOffice.org wiki

[First Name] = "Andrew"
[DéjàVu] = 2
Working With Variables
Implicit Variable Declaration
Overview of a Basic Program
Basic languages are designed to be easy to use. As a result, OpenOffice.org Basic enables the creation of a variable
through simple usage and without an explicit declaration. In other words, a variable exists from the moment that
you include it in your code. Depending on the variables that are already present, the following example declares
up to three new variables:
a = b + c
Declaring variables implicitly is not good programming practice because it can result in the inadvertent
introduction of a new variable through, for example, a typing error. Instead of producing an error message, the
interpreter initializes the typing error as a new variable with a value of 0. It can be very difficult to locate errors of
this kind in your code.
Explicit Variable Declaration
To prevent errors caused by an implicit declaration of variables, OpenOffice.org Basic provides a switch called:
Option Explicit
This must be listed in the first program line of each module and ensures that an error message is issued if one of
the variables used is not declared. The Option Explicit switch should be included in all Basic modules.
In its simplest form, the command for an explicit declaration of a variable is as follows:
Dim MyVar
This example declares a variable with the name MyVar and the type variant. A variant is a universal variable that
can record all conceivable values, including strings, whole numbers, floating point figures, and Boolean values.
Here are a few examples of Variant variables:
MyVar = "Hello World" ' Assignment of a string
MyVar = 1 ' Assignment of a whole number
MyVar = 1.0 ' Assignment of a floating point number
MyVar = True ' Assignment of a Boolean value
The variables declared in the previous example can even be used for different variable types in the same program.
Although this provides considerable flexibility, it is best to restrict a variable to one variable type. When
OpenOffice.org Basic encounters an incorrectly defined variable type in a particular context, an error message is
generated.
Use the following style when you make a type-bound variable declaration:
Dim MyVar As Integer ' Declaration of a variable of the integer type
The variable is declared as an integer type and can record whole number values. You can also use the following
style to declare an integer type variable:
Dim MyVar% ' Declaration of a variable of the integer type
The Dim instruction can record several variable declarations:
Dim MyVar1, MyVar2
If you want to assign the variables to a permanent type, you must make separate assignments for each variable:
Dim MyVar1 As Integer, MyVar2 As Integer
If you do not declare the type for a variable, OpenOffice.org Basic assigns the variable a variant type. For
Chapter 2 · The Language of OpenOffice.org BASIC 11