Lesson 4 PowerPoint

Microsoft Visual Basic 2005 BASICS

Lesson 4

Mathematical Operators

Microsoft Visual Basic 2005 BASICS 2

Objectives

Describe the purpose of operators and how calculations are performed in Visual Basic.

Create label controls. Use the addition and assignment

operators.


Objectives (cont.)

Use text boxes to get data from the user and use the Val function to extract a numeric value from a text box.

Split code statements among the lines in the code window.

Use the subtraction operator. Use unary minus.


Objectives (cont.)

Use the multiplication and division operators with the Fix function to remove the fractional portion of numbers.

Perform integer division and use the modulus operator.


Performing Calculations in Visual Basic

Visual Basic allows you to use mathematical equations in your programs.

Operators Symbols that perform specific operations in

Visual Basic statements


Performing Calculations in Visual Basic (cont.)


Creating Label Controls

Label control Used to place text in a form

Sometimes a label is used to identify a text box. May also be used to add a title or message

to a form


Creating Label Controls (cont.)

Labels can also be used to provide output. To provide output, you write code for the

desired calculation.


Using the Addition and Assignment Operators

The addition operator (+) and the assignment operator (=) Perform just as you would expect

The term “hard-coded” Information entered directly into the code Cannot change while the program runs

Literals Values keyed directly into source code


Using the Addition and Assignment Operators (cont.)


Using Text Boxes and the Val Function

Text boxes Fields placed on dialog boxes and in other

windows Allow the user to enter a value

The Text property of a text box Specifies what text will appear on the text

box


Using Text Boxes and the Val Function (cont.)


How Text Differs from Numeric Data

Text Can include letters, symbols, and numbers Treated differently than strictly numeric

information Numbers in a text box must be converted

to a true numeric value before they can be used in a calculation.


Using the Val Function

Val function Takes numbers that are in text format Returns a numeric value that can be used

in calculations Syntax example

lblTotal.Text = Val(txtPrice.Text) + Val(txtSalesTax.Text)


Splitting Code Statements among Lines

Visual Basic provides a way to split a line of code among two or more lines.

Line-continuation character Within a line of code, you can key the

underscore. Tells the compiler to skip the next line Treats the text there as if it were a part of

the same line


Splitting Code Statements among Lines (cont.)


Using the Subtraction Operator

The subtraction operator Subtracts the value to the right of the

operator from the value to the left of the operator


Using the Subtraction Operator (cont.)


Using Unary Minus

Unary minus operator Performs negation

Making a positive value negative Or making a negative value positive

The addition operator can be used as a unary plus.


Using Unary Minus (cont.)


Using Fix

Truncation Drops the fractional part of a number

Fix function Returns a truncated whole number


Using Fix (cont.)


Performing Integer Division and Using the Modulus Operator

Integers are whole numbers. Visual Basic provides two special

operations Integer division Modulus


Performing Integer Division

Integer division Returns only the whole number portion of

the division of integers Integer division is performed using the

backslash (\).


Performing Integer Division (cont.)


Using the Modulus Operator

Modulus returns the remainder of integer division.

The modulus operator is (Mod).


Summary

Visual Basic allows you to use mathematical equations in your programs.

Operators are symbols that perform specific operations in Visual Basic statements.

The addition operator (+) adds values.


Summary (cont.)

The assignment operator (=) assigns the result of the expression on the right of the operator to the item to the left of the operator.

The subtraction operator (–) subtracts the value to the right of the operator from the value to the left of the operator. It can be used to perform negation and is then called the unary minus.


Summary (cont.)

Values keyed directly into Visual Basic code are called hard-coded values or literals.

Text boxes are the fields placed on dialog boxes and in other windows that allow the user to enter a value.


Summary (cont.)

The numbers in a text box are considered to be text characters. To use the numbers as actual values in a calculation, the Val function must be used to convert the numeric text to a numeric value.


Summary (cont.)

When a line of code is long, you can split the code into two lines in the Code window by keying an underscore at the end of the line and continuing the statement on the next line. The underscore is called the line-continuation character.


Summary (cont.)

Placing an apostrophe in code allows you to enter text (called a comment) into the code. Everything from the apostrophe to the end of the line will be ignored.

Multiplication is represented by an asterisk (*). Division is represented by a forward slash (/).


Summary (cont.)

The Fix function removes the fractional portion of a number and performs an operation called truncation.

Integer division is represented by a backward slash (\) and returns only the whole number portion of the division of integers.

The modulus operator (Mod) returns the remainder of integer division.

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