Arithmetic: Creating Expressions With Variables And Operators

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Microsoft Visual Studio 2005/.NET Framework 2.0

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Microsoft Visual Studio 2008/.NET Framework 3.5

Visual Basic Language Concepts

Arithmetic: Creating Expressions With Variables And Operators

In this lesson, you will learn how to create expressions to perform arithmetic and then return values.

An expression is a segment of code that performs arithmetic and then returns a value. For example, a simple addition expression is shown below.

5 + 4

The expression 5 + 4 returns the value 9 when evaluated and is made up of two parts: the operands (5 and 4), which are the values that the operation is performed on, and the operator (+), which specifies the operation to be performed.

Using Values Returned by Expressions

For an expression to be useful, you must do something with the value that is returned. The most common thing to do is to assign it to a variable, as shown below.

Visual Basic

Dim anInteger As Integer = 5 + 4

This example declares a new Integer variable called anInteger and assigns the value returned by 5 + 4 to it.

Arithmetic Operators

A common use for expressions is to perform arithmetic on variables: addition, subtraction, multiplication, or division. The following table describes the operators commonly used for arithmetic.

Operator	Description	Example
+ (addition)	Returns the sum of two operands	5 + 4
- (subtraction)	Returns the difference of two operands	5 - 4
* (multiplication)	Returns the product of two operands	5 * 4
/ (division)	Returns the quotient of two operands	5 / 4

The kind of variable that you use when performing arithmetic can affect the result. Dividing two numbers often results in a return value that is not a whole number. For example, when you divide 3 by 2, the result is 1.5. If you assigned the return value of that expression to an Integer variable, it would be rounded to the nearest whole number, 2. When performing division, you should use a Double variable to store the return value.

Note
You can also convert a variable from one data type to another by using the conversion functions of Visual Basic. For more information, see Closer Look: Converting from One Variable Type to Another.

Try It!

To add numbers

On the File menu, choose New Project.
In the New Project dialog box, in the Templates pane, click Windows Application.
In the Name box, type Arithmetic and then click OK.

A new Windows Forms project opens.
From the Toolbox, drag two Textbox controls onto the form.
From the Toolbox, drag a Button control onto the form.
Double-click the Button to open the Code Editor.
In the Button1_Click event procedure, type the following code.
Visual Basic
```
Dim A As Double = Textbox1.Text
Dim B As Double = Textbox2.Text

MsgBox(A + B)
MsgBox(A - B)
MsgBox(A * B)
MsgBox(A / B)
```
The first two lines declare the variables A and B, which will hold the numeric values used in this program, and assign the values of the two TextBox controls (their text) to the variables A and B.

The final four lines create expressions with the two variables and each of the basic arithmetic operators, and display the results of those expressions in a message box.
Press F5 to run the application.
Type a number in each of the text boxes and click Button1.

Note

If you type any other character into the text boxes, an error will occur.

Expressions are created using the two numbers that you enter and each of the four basic arithmetic operators (addition, subtraction, multiplication, and division). The result of each expression is displayed in a message box.

Note
If you type any other character into the text boxes, an error will occur.

Next Steps

In this topic, you learned about creating and using expressions. You also learned about operands and operators, and how to construct an expression. At this point, you can either continue to the next lesson, Comparisons: Using Expressions to Compare Values or learn more about converting variables to different types in Closer Look: Converting from One Variable Type to Another. If you choose "Closer Look," you will complete it and then proceed to the next lesson.

Tasks

Closer Look: Converting from One Variable Type to Another

Concepts

Arithmetic Operators in Visual Basic