1. Section 3.3 Numbers Arithmetic Operations Variables
Incrementing the Value of a Variable
Built-In Functions:
Math.Sqrt
Int
Math.Round

2. Numbers continued The Integer Data Type Multiple Declarations
Parentheses
Three Types of Errors

3. Arithmetic Operations
Numbers are called numeric literals
Five arithmetic operations in VB.NET
+ addition
- subtraction
* multiplication
/ division
^ exponentiation
Think about Precedence !

4. Variables In VB.Net variable name can be up to
characters long
Must Begin with a Letter or _Underscore
Can Consists only of Letter, Numbers, Underscore
Not Case Sensitive
Convention is to write them in Lower case except 1st letters of additional words

5. Variables Declaration: Assignment: Dim speed As Double speed = 50
Data type
Variable name
Assignment:
speed = 50

6. Variables Declaration: Dim staffMembers As Integer
Integer Variable can take Whole
numbers from -2 billion to + 2
billion

7. Variable Declaration Dim speed As Double
Dim a As Integer (Used mainly for counting)
Dim b As String

8. Display Numeric Literals
lstBox.Items.Add(n)
Use lstBox.Items.Clear() to remove all the current content of the list box
Here Add is a Method – a process that performs a task for a particular object.
If ( ) contain (Numeric Expression) then it first evaluates the expression.

9. Display Numeric Literals
lstResults.Items.Add(1.2 * 10 ^34)
1.2 E + 34
lstResults.Items.Add(n+v)

10. Initialization Numeric variables are automatically initialized to 0:
Dim varName As Double
To specify a nonzero initial value
Dim varName As Double = 50
declares a variable named varName to be of type Double. Actually, the Dim statement
causes the computer to set aside a location in memory with the name varName. Since
varName is a numeric variable, the Dim statement also places the number zero in that
memory location. (We say that zero is the initial value or default value of the variable.)

11. Incrementing To add 1 to the numeric variable var Or as a shortcut
var = var + 1
Or as a shortcut
var +=1

12. Multiple Declarations
Dim a, b As Double
Two other types of multiple-declaration statements are
Dim a As Double, b As Integer
Dim c As Double = 2, b As Integer = 5

13. Functions Math.Sqrt(9) is 3 Int(2.7) is 2 Int(2) is 2 Int(-2.7) is –3
Math.Round(2.7) is 3
Math.Round(2.317, 2) is 2.32

14. Three Types of Errors
Syntax error
Run-time error
Logic error

15. Comments
Declaring variables at the beginning of event procedure is a good habit
Keywords can’t be used as names of variables
Names given to variables are also called identifiers
What will be the out put for Math.Sqrt(-1)
NaN

16. Comments 1/0 will give infinity 1/infinity will give 0 As answer
When n is 2.5, 1.5, etc then it rounds to the nearest even number
Math.Round(2.5) = 2
Math.Round(3.5) = 4

17. 3.4 Strings Variables and Strings
Using Text Boxes for Input and Output
Concatenation
ANSI Character Set
String Properties and Methods:
Length
ToUpper
Trim
ToLower
IndexOf
Substring

18. Strings continued The Empty String Initial Value of a String
Option Strict
Internal Documentation
Line-Continuation Character

19. Let’s talk about Strings
A string literal is a sequence of characters that is treated as a single item.
Strings are combined by concatenation
Eg. str1 & str2
“Santosh”& “ Panchal” = Santosh Panchal
A string variable is a name used to refer to a string.
Allowable names are same as numeric Var

20. Variables and Strings
Private Sub btnDisplay_Click(...) Handles btnDisplay.Click
Dim today As String
today = "Monday"
With lstOutput.Items
.Clear()
.Add("hello")
.Add(today)
End With
End Sub
Pay Attention to “With”

21. Using Text Boxes for Input and Output
The contents of a text box is always a string
Input example
strVar = txtBox.Text
Output example
txtBox.Text = strVar

22. Data Conversion
Because the contents of a text box is always a string, sometimes you must convert the input or output(type casting)
numVar = CDbl(txtBox.Text)
txtBox.Text = CStr(numVar)
Converts a String to a Double
Converts a number to a string

23. Concatenation Combining two strings to make a new string
This is a String expression
quote1 = "The ballgame isn't over, "
quote2 = "until it's over."
quote = quote1 & quote2
txtOutput.Text = quote & " Yogi Berra"
Displays
The ball game isn't over until it's over. Yogi Berra

24. ANSI Character Set
A numeric representation for every key on the keyboard

25. ddd Chr(n) will display a string with ANSI value n.
Asc(str) will display the ANSI value of the first character of str.
Eg. txt.Box.Text = Chr(65)  A
lstBox.Items.Add(Asc(“Apple”)) 65
txtBox.Text = “32”&Chr(176)& “Fahrenheit”
32o Fahrenheit

26. String Properties and Methods:
Imp. - A string is an OBJECT
"Visual".Length is 6.
"Visual".ToUpper is VISUAL.
"123 Hike".Length is 8.
"123 Hike".ToLower is 123 hike.
"a" & " bcd ".Trim & "efg" is abcdefg.

27. More String Properties and Methods:
"fanatic".Substring(0, 3) is "fan".
"fanatic".IndexOf("ati") is 3.
"fanatic".Substring(4, 2) is "ti".
"fanatic".IndexOf("a") is 1.
"fanatic".Substring(4) is "tic".
"fanatic".IndexOf("nt") is –1.
Let’s Do Ex. 6 – Page 97

28. The Empty String
The string "", which contains no characters, is called the empty string or the zero-length string.
The statement lstBox.Items.Add("") skips a line in the list box.
The contents of a text box can be cleared with either the statement
txtBox.Clear()
or the statement
txtBox.Text = ""

29. Initial Value of a String
By default the initial value is Nothing
Strings can be given a different initial value as follows:
Dim today As String = "Monday"

30. Option Strict
VB.NET allows numeric variables to be assigned strings and vice versa, a poor programming practice.
To turn this feature off, put the following statement at the very top of the code window
Option Strict On

31. Internal Documentation
Other people can easily understand the program.
You can understand the program when you read it later.
Long programs are easier to read because the purposes of individual pieces can be determined at a glance.

32. Line-Continuation Character
A long line of code can be continued on another line by using underscore (_) preceded by a space
msg = "640K ought to be enough " & _
"for anybody. (Bill Gates, 1981)"

33. 3.5 Input and Output Formatting Output with Format Functions
Formatting Output with Zones
Reading Data from Files
Getting Input from an Input Dialog Box
Using a Message Dialog Box for Output

34. Formatting Output with Format Functions
String Value
FormatNumber( ,1)
12,345.6
FormatCurrency( ,2)
$12,345.63
FormatPercent(0.185,2)
18.50%

35. Formatting Output with Zones
Use a fixed-width font such as Courier New
Divide the characters into zones with a format string.
Dim fmtStr As String = "{0, 15}{1, 10}{2, 8}"
lstOutput.Items.Add(String.Format(fmtStr, data0, data1, data2))

36. Inputting Data
Data can be stored in files and accessed with a StreamReader object or supplied by the user with an input dialog box.

37. Steps to Use StreamReader
Execute a statement of the form
Dim readerVar As IO.StreamReader = _
IO.File.OpenText(filespec)
or the pair of statements
Dim readerVar As IO.StreamReader
readerVar = IO.File.OpenText(filespec)
Assume the file contains one item of data per line.
Read items of data in order, one at a time, from the file with the ReadLine method.
strVar = readerVar.ReadLine
After the desired items have been read from the file, terminate the communications link
readerVar.Close()
1. Execute a statement of the form
Dim readerVar As IO.StreamReader
A StreamReader is an object from the Input/Output class that can read a stream of
characters coming from a disk or coming over the Internet. The Dim statement
declares the variable readerVar to be of type StreamReader.
2. Execute a statement of the form
readerVar = IO.File.OpenText(filespec)
where filespec identifies the file to be read. This statement establishes a communi-cations
link between the computer and the disk drive for reading data from the disk.
Data then can be input from the specified file and assigned to variables in the pro-gram.
This assignment statement is said to “open the file for input.”
Just as with other variables, the declaration and assignment statements in Steps
2 and 3 can be combined into the single statement
Dim readerVar As IO.StreamReader = IO.File.OpenText(filespec)
3. Read items of data in order, one at a time, from the file with the ReadLine method.
Each datum is retrieved as a string. A statement of the form
strVar = readerVar.ReadLine
causes the program to look in the file for the next unread line of data and assign it
to the variable strVar. The data can be assigned to a numeric variable if it is first
converted to a numeric type with a statement such as
numVar = CDbl(readerVar.ReadLine)
Note: If all the data in a file have been read by ReadLine statements and another item
is requested by a ReadLine statement, the item retrieved will have the value Nothing.
4. After the desired items have been read from the file, terminate the communications
link set in Step 3 with the statement
readerVar.Close()

38. Getting Input from an Input Dialog Box
stringVar = InputBox(prompt, title)
fileName = InputBox("Enter the name " _
& "of the file containing the " & _
"information.", "Name of File")

39. Using a Message Dialog Box for Output
MsgBox(prompt, , title)
MsgBox("Nice try, but no cigar.", , "Consolation")
MsgBox(prompt, , title)
is executed, where prompt and title are strings, a message dialog box appears with prompt
displayed and the title bar caption title and stays on the screen until the user presses
Enter, clicks on the box in the upper-right corner, or clicks OK. For instance, the state-ment
MsgBox("Nice try, but no cigar.", , "Consolation")

40. Have Fun!
V.B. is Enjoyable, especially with Visual Studio.Net