Visual Basic 'NET BASICS

1
Visual Basic .NET BASICS

• Lesson 4
• Mathematical Operators

2
Objectives

• Describe the purpose of operators and how
  calculations are performed in Visual Basic .NET.
• Create label controls.
• Use the addition and assignment operators.
• Use text boxes to get data from the user and use
  the Val function to extract a numeric value from
  a text box.

3
Objectives (continued)

• Split code statements among the lines in the code
  window.
• Use the subtraction operator.
• Use unary minus.
• 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.

4
Performing Calculations in Visual Basic .NET

• Like other programming languages, Visual Basic
  .NET allows you to use mathematical equations in
  your programs.
• Operators are symbols that perform specific
  operations in Visual Basic .NET statements.
• The symbols and / are used to represent
  multiplication and division in Visual Basic .NET.

5
Creating Label Controls

• The Label control is used to place text in a
  form.
• Sometimes a label is used to identify a text box
  or to add a title or message to a form.
• Labels can also be used to provide output.
• To provide output, you write code for the desired
  calculation.

6
Using the Addition and Assignment Operators

• The addition operator () and the assignment
  operator () perform just as you would expect.
• The term hard-coded refers to information that is
  entered directly into the source code and cannot
  change while the program runs.

7
Using Text Boxes and the Val Function

• Text boxes are the fields placed on dialog boxes
  and in other windows that allow the user to enter
  a value.
• The Text property of a text box specifies what
  text will appear on the text box.

8
How Text Differs from Numeric Data

• In a computer, text which can include letters,
  symbols, and numbers is 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.
• Understand that the characters entered in text
  boxes need to be converted from text to a
  numerical value before mathematical operations
  can be performed.

9
Using the Val Function

• The conversion necessary to convert the numeric
  text characters in a text box to numeric values
  is done by the Val function.
• The Val function takes numbers that are in text
  format and returns a numeric value that can be
  used in calculations.

10
Splitting Code Statements among Lines

• Visual Basic .NET provides a way to split a line
  of code among two or more lines.
• Within a line of code, you can key the
  underscore, known as the line-continuation
  character.
• The line-continuation character tells the
  compiler to skip the next line and treat the text
  there as if it were a part of the same line.

11
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.

12
Using Unary Minus

• You can use the subtraction operator as unary
  minus to perform negation, which means making a
  positive value negative or making a negative
  value positive.
• The addition operator can be used as a unary
  plus.

13
Using Fix

• Most programming languages include a function
  that drops the fractional part of a number.
• This process is called truncation.
• In Visual Basic .NET, the Fix function returns a
  truncated whole number.

14
Performing Integer Division and Using the Modulus
Operator

• In computer programming, there are times when you
  want to work exclusively with whole numbers
  called integers.
• For cases when you want to work strictly with
  integers, Visual Basic .NET provides two special
  operations integer division and modulus.

15
Performing Integer Division

• Integer division returns only the whole number
  portion of the division of integers.
• Integer division is performed using the backslash
  (\).

16
Using the Modulus Operator

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

17
Summary

• Visual Basic. NET allows you to use mathematical
  equations in your programs.
• Operators are symbols that perform specific
  operations in Visual Basic. NET statements. The
  addition operator () adds values. The assignment
  operator () assigns the result of the expression
  on the right of the operator to the item to the
  left of the operator.

18
Summary (continued)

• The subtraction operator () subtracts the value
  to the right of the operator from the value to
  the left of the operator. The subtraction
  operator can be used to perform negation. When
  used in this way, the subtraction operator is
  called the unary minus.
• Values keyed directly into Visual Basic. NET code
  are called hard-coded values or literals.

19
Summary (continued)

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

20
Summary (continued)

• 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.
• 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.

21
Summary (continued)

• Multiplication is represented by an asterisk ().
  Division is represented by a forward slash (/).
• The Fix function removes the fractional portion
  of a number. The Fix function performs an
  operation called truncation.
• Integer division is represented by a backward
  slash (\). Integer division returns only the
  whole number portion of the division of integers.
  The modulus operator (Mod) returns the remainder
  of integer division.