Procedure & Functions

Procedure

Sub Procedures

A Sub procedure is a block of code that is executed in response to an event.

By breaking the code in a module into Sub procedures, it becomes much easier to find or modify the code in your application.

Syntax:

[Private|Public][Static]Sub procedurename (arguments)

statements

End Sub

Each time when procedure is called, the statements between Sub and End Sub are executed. Sub procedures can be placed in standard modules, class modules, and form modules.

Sub procedures are by default Public in all modules, that means they can be called from anywhere in application.

Note that:

Sub Procedures are the procedures that do not return a value.

The arguments for a procedure are like a variable declaration.

Event Procedures

When an object in Visual Basic recognizes that an event has occurred then it automatically invokes event procedure

That event procedure will use procedure name corresponding to that event.

Syntax:

Private Sub Form_eventname (arguments)

statements

End Sub

CmdSave_Click():-Here Click is an event and CmdSave_Click() is the procedure associated with it.

Syntax for a Control Event:

Private Sub Control_Eventname(arguments)

Statements Block

End sub

Syntax for a Form Event:

Private Sub Form_eventname(arguments)

Statements Block

End sub

Example:

Private Sub Form_Load().

This is the main event procedure for a form .When a form is loaded in application then this procedure is called first.

General Procedures

A general procedure tells the application how to perform a specific task. Once a generalprocedure is defined, it must be specifically invoked by the application.

General procedure remains idle until called upon to respond to events caused by the user or by system.

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Why create general procedures?

One reason is that several different event procedures might need the same task repeatedly.

A good programming strategy is to put common statements in a separate procedure (a general procedure). An event procedure calls that general procedure.

This eliminates the need to duplicate code and also makes the application easier to maintain.

Example:

Suppose you display some message after each event code execution then you will useevent procedure.

For adding procedure to your application follow the steps given below:

(1) Go to Tools menu and select Add Procedure form. Or, Use key combination Alt+T+P.

The window will be shown like this:

(2) Write name of procedure Display in the name Box and select type Sub according to figure given above.

(3) Write code for display() after Clicking OK in the previous Step.The code Window will display like this:

(4) Now call procedure in any event associated your application.

( Calling Procedure display() )

Procedure   Function Procedures   Function Procedures return values. you can use Function statement to write your ownFunction procedures.   Like a Sub procedure, a Function procedure is a separate procedure that can take arguments, perform a series of statements, and change the value of its arguments.   Syntax:   [Private|Public][Static]Function procedurename (arguments) [As type] statements End Function   Note that:   1.You call a function by including the function procedure name and arguments on the right side of a larger statement or expression (returnvalue = function()).   2.Function procedures have data types, just as variables. This determines the type of the return value.   3.You return a value by assigning it to the procedurename itself.   Example:   Public function Addition(a,b) Addition=a+b End Function   Here Function addition is declared .It takes two arguments and then add these two values. It returns sum of two values.   For Animated Presentation Click Here         Procedure   Property Procedures   Property procedures are the procedures that return values and also assign values to the property of objects. Visual Basic provides three kinds of property procedures, as described in the following table.   Procedure Procedure Property Get Returns the value of a property. Property Let ets the value of a property. Property Set Sets the value of an object property.   Property procedures are defined in class modules.   Note that: If you need to perform a task each time then you need to use a property procedure. Once it is defined, it executes automatically without needing an explicit call each time.         Functions   Visual Basic Functions   A function is a preprogrammed calculation .It can be carried out on request from any point in a Visual Basic program. A function takes one or more arguments and returns a single value and it can be included in an expression.   Argument: It is a value on which a function or procedure operates. For example, in the Visual Basic statement Str(10), number 10 is the argument.   Visual Basic includes built-in functions like Sqr, Cos or Chr etc.We are discussing some of them here:   (1) Sqr() Returns a Double specifying the square root of a number.   Syntax Sqr(number)   (2) ABS() Returns the absolute, positive value of the given numeric expression.   Syntax ABS(numeric_expression) Arguments numeric_expression Is an expression of the exact numeric or approximate numeric data type category. Return Types Returns same type as numeric_expression.   (3) POWER() Returns value of given expression to the specified power.   Syntax POWER(numeric_expression, y) Arguments numeric_expression Is an expression of the exact numeric or approximate numeric data type category. y Is the power to which to raise numeric_expression. y can be an expression of the exact numeric or approximate numeric data type category.   (4) FLOOR () Returns largest integer less than or equal to the given numeric expression.   Syntax FLOOR(numeric_expression) Arguments numeric_expression Is an expression of exact numeric or approximate numeric data type category. Return Types Returns the same type as numeric_expression.   For Example: FLOOR(122.45), Return value=122 FLOOR(-123.45) ,Return value=124   (5) Round() Returns a numeric expression, rounded to the specified length or precision.   Syntax ROUND (numeric_expression, length) Arguments numeric_expression Is an expression of the exact numeric or approximate numeric data type category. length Is the precision to which numeric_expression is to be rounded. length must be int. When length is a positive number, numeric_expression is rounded to the number of decimal places specified by length. When length is a negative number, numeric_expression is rounded on the left side of the decimal point, as specified by length. Return Types Returns the same type as numeric_expression.   For Example: Round(123.4545,2) ,Return Value=123.4500   (6) SQUARE() Returns the square of given expression.   Syntax SQUARE(float_expression) Arguments float_expression Is an expression of type float. Return Types float   (7) PI () Returns the constant value of PI.   Syntax PI() Return Types float   (8) SIGN () Returns the positive (+1), zero (0), or negative (-1) sign of the given expression.   Syntax SIGN(numeric_expression) Arguments numeric_expression Is an expression of the exact numeric or approximate numeric data type category. Return Types Float   (9) LOG10 () Returns the base-10 logarithm of the given float expression.   Syntax LOG10(float_expression) Arguments float_expression Is an expression of the float data type. Return Types Float   (10) RAND () Returns a random float value between 0 and 1.   Syntax RAND([seed]) Arguments seed Is an integer expression (int) giving the starting value. Return Types float