Variables

            Store information temporarily

            Have a short easy to remember name used by the programmer

Dim Statement

Used to declare a variable – gives the variable a name, reserves room in memory, tells the compiler what kind (type) of data it will hold (also called variable typing).

Usually done at the top of a procedure or code module

Dim LastName as String

Later the variable can have contents deposited to it with the assignment statement

LastName=”Jefferson”

And later still, the variables contents can be dropped into a VB control

Label1.Text = LastName

Or passed as an argument to a procedure or function.  The variable Prompt is passed to the InputBox function.  The results as assigned to the FullName variable.

Dim FirstName as String

MsgBox("Mr. " & LastName “please enter your first name.”)

FirstName = InputBox(Prompt)

Variable Name Rules

• Start with a letter or underscore

• Contain letters, underscores, numbers – no special characters, no punctuation

• Limit is 255 characters, but 33 is more reasonable

• Don’t use VB keywords, objects or properties as variable names

• “Camel Casing” is common – use more than one word, but capitalize the first letter of each

• Use of a prefix is common – strLastName says the variable is a string

Variable Types

Here are the most common types to start out with.  There are many others.

 String – treat data as separate characters.  No math will be done with this.

Integer – positive whole numbers.

Single – numbers with places right of the decimal point, positive and negative.

Declare More Than One Variable In A Single Statement

You can declare more than one variable in a single statement as long as they are the same type, and if you separate the names with a comma. 

Dim LastName, FirstName as String

Constants

Constants are variables with a set value which will never change. Examples include Pi.  These are given the type Const.

 Const Pi as Double = 3.14159265

 When they are declared Public, they are available to all objects, functions and code modules. 

Public Const Pi as Double = 3.14159265

UDTs

You can make your own data type as well, which is called a User-Defined Type.  These are used when a set of variables are often used together.

Structure FullName

     Dim First as String

     Dim Middle as String

     Dim Last as String

The lines above define a user defined type named FullName.  This data type store the three variables under it.

Dim Student as FullName

     Student.First = “John”

 The lines above create a new variable called Student.  This variable has the type FullName which is a user defined type consisting of three variables.  The second statement assigns the variable First which is part of Student with the word John.

It’s just another way of working with variables that might be helpful in certain cases.