1. Data Types 1

3. Single or Double ?
Visual Basic provides data type Single for storing single-precision floating-point numbers.
Data type Double requires more memory to store a floating-point value, but is more accurate than type Single.
Type Single is useful in applications that need to conserve memory and do not require the accuracy provided by type Double.

4. Dim statement declares variable Dim varname As type [ = initexpr ]
Declaring a Variable
Dim statement declares variable
Dim varname As type [ = initexpr ]
varname is variable name
As type contains data type of variable
Optional initexpr contains the initial value of a variable

5. Initialize a variable when declaring it
Declaring a Variable
Initialize a variable when declaring it
New to VB .NET
Declare an Integer variable and store the value 30 in the variable
Dim mintYearTerm As Integer = 30

6. Declaring a Variable
Possible to declare multiple variables on the same line
Dim mintYearTerm, mintMonthTerm As Integer

7. Declaring Constants Declare constants with the Const statement.
Constants are similar to variables – constants are values that are stored to memory locations; however, a constant cannot have its value change during program execution – constant values are generally fixed over time.
Examples:
Const SALES_TAX_RATE_SINGLE As Single = F
Const BIG_STATE_NAME_STRING As String = "Alaska"
Const TITLE_STRING As String = "Data Entry Error"
Const MAX_SIZE_INTEGER As Integer = 4000

8. Declaring Constants
Follow these rules for assigning numeric values to constants:
You can use numbers, a decimal point, and a plus (+) or minus (-) sign.
Do not include special characters such as a comma, dollar sign, or other special characters.
Append one of these characters to the end of the numeric constant or variable to denote a data type declaration. If you do not use these, a whole number is assumed to be Integer and a fractional value is assumed to be Double.
Decimal D 40.45D
Double R R
Integer I 47852I
Long L L
Short S 2588S
Single F F

9. Strings
Such as sentences, words, letters of the alphabet, names, telephone numbers& addresses.
A string constant is a sequence of characters that is treated as a single item.

10. Strings quote1 = “ The ball game isn’t over “
quote2 = “ until it is over “
quote = quote1 & “ , “ & quote2
Console.WriteLine ( quote ) 
The ball game isn’t over , until it is over

11. Examining Variable Types
IsNumeric()
IsDate()
System.Date.IsLeapYear (2001)  False

12. Boolean Data Type It stores True (1) / False (0)
Any non-zero value will be considered as TRUE.
These variables are combined with the logical operators.. AND, OR & NOT.

13. Converting Input Data Types
Text property always stores string values, even if the string looks like a number.
Parse method – converts a string value to an equivalent numeric value for storage to a numeric variable.
Parse means to examine a string character by character and convert the value to another format such as decimal, integer, or string.
Dim QuantityInteger As Integer = Integer.Parse(TextBox2.Text)

14. Conversion Between Data Types
1. Methods belong to the System.Convert class
ToInt16 converts value to a Short
ToInt32 converts value to an Integer
ToInt64 converts value to a Long
ToDouble converts value to a Double
ToSingle converts value to a Single
ToString converts value to a String

15. Conversion Between Data Types
Dim msngInput As Single = 3.44
Dim mstrInput As String = "3.95"
Dim mintOutput As Integer
Dim msngOutput As Single
Convert a Single to an Integer
mintOutput = System.Convert.ToInt32(msngInput)
Convert a String to an Integer
mintOutput = System.Convert.ToInt32(mstrInput)
Convert a String to a Single
msngOutput = System.Convert.ToSingle(mstrInput)

16. Conversion Between Data Types
2. CType and named functions:
CType method
Dim A As string = “34.56”
Dim B As Double
B = CType ( A , Double) / 1.14
Older versions of VB used named functions to convert values. Examples are the CDec (convert to Decimal) and CInt (convert to Integer):
PriceDecimal = CDec(TextBox1.Text)
QuantityInteger = CInt(TextBox2.Text)
CDate, CDec, CStr, CLng, CChar, CBool, CByte

17. Implicit Conversion
Implicit Conversion – this is conversion by VB from a narrower to wider data type (less memory to more memory) – this is done automatically as there is no danger of losing any precision.
In this example, an integer (4 bytes) is converted to a double (8 bytes):
BiggerNumberDouble = SmallerNumberInteger