Visual Basic offers different types of procedures to execute small sections of coding
in applications. The various procedures are elucidated in details in this section.
Basic programs can be broken into smaller logical components called Procedures.
Procedures are useful for condensing repeated operations such as the frequently
used calculations, text and control manipulation etc. The benefits of using procedures
It is easier to debug a program
a program with procedures, which breaks a program into discrete logical limits.
Procedures used in one program can act as building blocks for other programs
with slight modifications.
A Procedure can be Sub, Function or Property Procedure.
A sub procedure can be placed in standard, class and form modules. Each time
the procedure is called, the statements between Sub and End Sub are executed.
The syntax for a sub procedure is as follows:
[Private | Public] [Static] Sub Procedurename [( arglist)]
arglist is a list of argument names separated by commas. Each argument acts
like a variable in the procedure. There are two types of Sub Procedures namely
general procedures and event procedures.
An event procedure is a procedure block that contains the control's actual
name, an underscore(_), and the event name. The following syntax represents the
event procedure for a Form_Load event.
Private Sub Form_Load()
Event Procedures acquire the declarations as Private by default.
A general procedure is declared when several event procedures perform the same
actions. It is a good programming practice to write common statements in a separate
procedure (general procedure) and then call them in the event procedure.
In order to add General procedure:
The Code window is opened for the module to which the procedure is to be added.
The Add Procedure option is chosen from the Tools menu, which opens
an Add Procedure dialog box as shown in the figure given below.
The name of the procedure is typed in the Name textbox
Under Type, Sub is selected to create a Sub procedure, Function
to create a Function procedure or Property to create a Property procedure.
Under Scope, Public is selected to create a procedure that
can be invoked outside the module, or Private to create a procedure that can be
invoked only from within the module.
We can also create a new procedure in the current module by typing Sub ProcedureName,
Function ProcedureName, or Property ProcedureName in the Code window. A Function
procedure returns a value and a Sub Procedure does not return a value.
Functions are like sub procedures, except they return a value to the calling
procedure. They are especially useful for taking one or more pieces of data, called
arguments and performing some tasks with them. Then the functions returns
a value that indicates the results of the tasks complete within the function.
The following function procedure calculates the third side or hypotenuse of
a right triangle, where A and B are the other two sides. It takes two arguments
A and B (of data type Double) and finally returns the results.
Function Hypotenuse (A As Double, B As Double) As Double
Hypotenuse = sqr (A^2 + B^2)
The above function procedure is written in the general declarations section
of the Code window. A function can also be written by selecting the Add Procedure
dialog box from the Tools menu and by choosing the required scope and type.
A property procedure is used to create and manipulate custom properties. It
is used to create read only properties for Forms, Standard modules and Class modules.Visual Basic provides three kind of property procedures-Property Let procedure that
sets the value of a property, Property Get procedure that returns the value of
a property, and Property Set procedure that sets the references to an object.