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jut a text explanation about Variables A Basic Note ! Just Refer. is Useful

jut a text explanation about Variables A Basic Note ! Just Refer. is Useful

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By vicky Jadhav

It is a good programming practice to give descriptive names to your variables.  In this way the variable's purpose can be more easily understood.  

Let's change the variable name of the previous example:->----->


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Dim intCount As Integer
   
  Command1.Caption = ""
  For intCount = 1 To 10
    Command1.Caption = Command1.Caption & intCount
  Next intCount
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Notice that the variable name now better describes what the variable is used for.  Also, by putting an abreviation of the variables type in front of the variable name you can always know this variable stores integer values.

The first character of any variable must be a letter.  The other characters in the variable name can be either letters or numbers.  

Certain variables can have one of these symbols as their last character:  %,&,,#,$.  More on this later.

No variable can have the same name as a Basic reserved word.  

Reserved words have special meaning to the Basic language.  The following are examples of Basic reserved words:  DIM, FOR, TO, STEP, NEXT.


		STARTING A NEW PROGRAM

If you have entered a program in Basic and wish to start a new one there are basically two ways to do this:

If you wanted to save the old program, you could simply create another button for your new code.  

If you do not need the old program simply highlight the text of the old program and delete it by pressing the [Delete] key.

Since we want to try another program choose one of the previously mentioned options now. Then enter this program:->------->

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Dim lngSalary As Long

  lngSalary = 10000
  MsgBox "" & lngSalary
  lngSalary = 40000
  MsgBox "" & lngSalary

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Run the program to see what happens.  

Notice that the variable "lngSalary" can be changed to any integer number during the course of the program.  

To assign a value to a variable you use the equal sign "=".

		
		VARIABLE TYPES


Whenever you use a variable in Basic you should assign it a variable type.  

There are six basic variable types, each having a special symbol to identify them:

% - Integer : -32,768 to 32767
& - Long Integer : -2,147,483,648 to 2,147,483,647
 - Single Precision : see VB help
# - Double Precision : see VB help
$ - String : see VB help
@ - Currency : see VB help


There are five other common types that do not have symbols:

Byte - 0 to 255
Boolean - True or False
Date - 1/1/100 to 1/31/9999
Object - any object reference
Variant - any data

		VARIABLE DECLARATIONS


Variable typing is very important in good programming.  Proper typing helps prevent errors or bugs in your programs, which can result in unusual behavior.

Notice the first line in the previous program we looked at:->------>

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Dim lngSalary As Long

  lngSalary = 10000
  MsgBox "" & lngSalary
  lngSalary = 40000
  MsgBox "" & lngSalary

+++++++++++++++++++++++++++++++++++++++++++

This line is an example of variable typing.


Variables should always be typed at the very start of your program.  
To type a variable you must declare it with the DIM keyword and then assign a type to the variable.  In this case the variable's type is "Long".

		STRING VARIABLES

In programming, text data is referred to in terms of strings.  Strings are any sequence of characters enclosed in quotation marks.  

For an example look at this program:->-------->

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Dim strFirstName As String
Dim strLastName As String

  strFirstName  = "Mike"
  strLastName = "Huete"
  MsgBox strLastName & ", " & strFirstName 

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			FUNCTIONS


Functions are not variables but often take variables as input.  When a function is called it completes a task and then outputs a value.


InputBox is a function:->--------->

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Dim strRad As String, strPrompt as String

  strPrompt = "Enter Radius: "
  strRad = InputBox(strPrompt)
  MsgBox "Area of circle: " & 3.14 * Val(strRad) ^ 2

+++++++++++++++++++++++++++++++++++++++++++

In this example, the InputBox function takes the strPrompt variable as input, requests a number from the user and returns a value that is put into the strRad variable.


In order to use the radius obtained from the InputBox command, the string value returned was converted to a numeric representation using the Val() function.  

			DATE & TIME


Functions do not always require input variables.  Two such functions generate the current date and time:  ->----->


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  MsgBox "Today's Date is: " & Date$ 
  MsgBox "The current Time is: " & Time$

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A constant is like a variable except that a constant's value can never change:->---------->

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Const PI = 3.14
Const PROMPT = "Enter Radius: "
Dim strRad As String

  strRad = InputBox(PROMPT)
  MsgBox "Area of circle: " & PI * Val(strRad) ^ 2

+++++++++++++++++++++++++++++++++++++++++++


Here we have two constants, a numeric constant, PI, and a string constant, PROMPT.

Many programmers like to use all capital letters for constants so that they won't be mistaken for variables.

			ARITHMETIC


With Basic you can easily perform all manner of arithmetic operations.  Look at this example: ->---------->

+++++++++++++++++++++++++++++++++++++++++++

Dim intResult As Integer

  intResult = (2 + 2)	        'addition
  MsgBox "2 + 2 = " & intResult
  intResult = (3 * 4)	        'multiplication
  MsgBox "3 * 4 = " & intResult
  intResult = (4 - 2)	        'subtraction
  MsgBox "4 - 2 = " & intResult
  intResult = (6 / 3)	        'division
  MsgBox "6 / 3 = " & intResult
  intResult = (2 ^ 3)	        'exponents
  MsgBox "2 ^ 3 = " & intResult

+++++++++++++++++++++++++++++++++++++++++++

Here the values of arithmetic expressions are appended to strings. This results in one string value that is used as input to the MsgBox function.


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