The student will be able to: What is Variable, constant Know how to declare variable and Constant Rule of naming variable and Constant Using Data type Scope of Variable and Constant Converting data output Format output Develop small project using calculator

1. CHAPTER-03
Variable
Constants
Culculation
Prepared by: Mr Pork Naron

2. Objective
 The student will be able to:
 What is Variable, constant
 Know how to declare variable and Constant
 Rule of naming variable and Constant
 Using Data type
 Scope of Variable and Constant
 Converting data output
 Format output
 Develop small project using calculator
Prepared by: Mr Pork Naron

3. Variable
 Provide a means to store data values that are
not stored in files.
 Support the computation of values through
their use in formulas in assignment
 Represent locations in a computer's memory
 are assigned a unique name for reference when
writing computer code statements.
Prepared by: Mr Pork Naron

4. DataType
Prepared by: Mr Pork Naron
DataType Description Bytes
Text Data
String Alphanumeric data such as letters of the alphabet Size varies
Char
Stores single Unicode characters (supports any international
language).
2
Numeric Data
Decimal often used to store dollars/cents 16
Double Double-precision numeric values with 14 digits of accuracy 8
Single Single-precision numeric values with 6 digits of accuracy 4
Short numeric values in the range -32,768 to 32,767 2
Integer
numeric values in the range -2,147,483,648 to
+2,147,483,647
4
Long numeric values that are very, very large 8

5. DataType(Cont)
Prepared by: Mr Pork Naron
DataType Description Bytes
Special DataType
Boolean True or False 2
Byte
Stores binary data of values 0 to 255 – can be used to store
ASCIIcharacter code values
1
Date Stores dates in the form 1/1/0001 to 12/31/9999 8
Object Any type of data 4

6. Naming Rules for
Variable and Constant
Prepared by: Mr Pork Naron
 Can be letters, digits, and the underscore,
but must begin with a letter
 cannot contain spaces or periods
 cannot be VB reserved words such as LET,
PRINT, DIM, or CONST
 are not case sensitive. This means that
TotalInteger, TOTALINTEGER, and
totalinteger are all equivalent names

7. Naming Convention
Prepared by: Mr Pork Naron
 Create meaningful names
 Avoid using abbreviations
 Begin each name with an uppercase letter and
capitalize each successive word in the name.
 Use mixed case (such as AmountDueDecimal) for
variables – use Uppercase for constant names
(such as TAX_RATE_SINGLE)

8. Declaring Variable & Constant
Prepared by: Mr Pork Naron
Variable
 Dim
 Eg: Dim EmployeeName as String
Constant
 Const
 Eg: Const Age as Integer=23

9. Scope of Variables and Constants
Prepared by: Mr Pork Naron
 Namespace : Public Shared(visible in whole
project)
 Module level: Private(variable), Const (
constant) – visile any procedure in specific form.
 Local : Dim(variable), Const (constant) visible
in only one procedure
 Block : Dim(variable), Const(constant) – visible
in only a portion of procedure

10. Converting Input Data Types
Prepared by: Mr Pork Naron
 Text property – always stores string
values, even if the string looks like a
number.
 Parse method – converts a value from
a Text property to an equivalent
numeric value or other types

11. Converting Variable Values to Output
Data Types
Prepared by: Mr Pork Naron
 Use (.ToString) method to convert
variable value to output data
 TxtOutput.text = Output.ToString()

12. Arithmetic Operators
Prepared by: Mr Pork Naron
 + Addition
 - Subtraction
 * Multiplication
 / Division
 ^ Exponentiation
 Integer Division
 Mod Modulus Division

13. Order of Precedence
Prepared by: Mr Pork Naron
1. Values enclosed inside
parentheses (xxxx)
2. Exponentiation ^
3. Multiplication and Division(*,/)
4. Addition and Subtraction (+, -)

14. Order of Precedence(cont)
Prepared by: Mr Pork Naron
Eg: Assume that: X=2, Y=4, and Z=3

15. Order of Precedence(cont)
Prepared by: Mr Pork Naron
• mathematical notation and the equivalent VB
expression

16. Format Function
Prepared by: Mr Pork Naron
 FormatCurrency
 BalanceDueTextBox.Text = FormatCurrency(BalanceDueDecimal)
 FormatNumber
 AmountTextBox.Text = FormatNumber(AmountDouble)
 FormatPercent
 PercentFinishedTextBox.Text = FormatPercent(FinishedSingle)
 FormatDate
 DateTextBox.Text = FormatDateTime(StartDate, DateFormat.ShortDate)
 DateTextBox.Text = FormatDateTime(StartDate, DateFormat.LongDate)
 TimeTextBox.Text = FormatDateTime(StartDateTime,
DateFormat.ShortTime)
 TimeTextBox.Text = FormatDateTime(StartDateTime,
DateFormat.LongTime)

17. Compute Lab
Prepared by: Mr Pork Naron
Develop Small Calculator