"Deep in the sea are riches beyond compare.
But if you seek safety, it is on the shore."

Inerface programming using Visual Basic 6.0. (COM)

'This application is an example of interface programming(COM) using VB
'Open the standard exe application
'Add five class module to the application

'Named the five class module as IMath,Add,Subtract,Multiply,Divide
'by Invincible(invincible@usa.com)
'IMath is the base class and other classes inherits IMath.
'Code to be written in IMath Class module mentioned below
'Prototype declaration of functions

Public Function Add(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

Public Function Subtract(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

Public Function Multiply(intNumber1 as integer,intNumber2 as integer)as double
'Do not write anything over here
End Function

Public Function Divide(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

'Code to be written in Add class module mentioned below
Option Explicit
'Inherits all methods and functions of IMath class
Implements IMath
Public Function IMath_Add(intNumber1 as integer,intNumber2 as integer)as integer
dim intNumber3 as integer
intNumber3=intNumber1+intNumber2
IMath_Add=intNumber3
End Function

Public Function IMath_Subtract(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

Public Function IMath_Multiply(intNumber1 as integer,intNumber2 as integer)as double
'Do not write anything over here
End Function

Public Function IMath_Divide(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

'Code to be written in Subtract class module mentioned below
Option Explicit
'Inherits all methods and functions of IMath class
Implements IMath
Public Function IMath_Add(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write over here
End Function

Public Function IMath_Subtract(intNumber1 as integer,intNumber2 as integer)as integer
dim intNumber3 as integer
intNumber3=intNumber1-intNumber2
IMath_Subtract=intNumber3
End Function

Public Function IMath_Multiply(intNumber1 as integer,intNumber2 as integer)as double
'Do not write anything over here
End Function

Public Function IMath_Divide(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

'Code to be written in Multiply class module mentioned below
Option Explicit
'Inherits all methods and functions of IMath class
Implements IMath
Public Function IMath_Add(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write over here
End Function

Public Function IMath_Subtract(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

Public Function IMath_Multiply(intNumber1 as integer,intNumber2 as integer)as double
dim intNumber3 as integer
intNumber3=intNumber1 * intNumber2
IMath_Multiply=intNumber3
End Function

Public Function IMath_Divide(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

'Code to be written in Divide class mentioned below
Option Explicit
'Inherits all methods and functions of IMath class
Implements IMath
Public Function IMath_Add(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write over here
End Function

Public Function IMath_Subtract(intNumber1 as integer,intNumber2 as integer)as integer
'Do not write anything over here
End Function

Public Function IMath_Multiply(intNumber1 as integer,intNumber2 as integer)as double
'Do not write anything over here
End Function

Public Function IMath_Divide(intNumber1 as integer,intNumber2 as integer)as integer
dim intNumber3 as integer
intNumber3=intNumber1 / intNumber2
IMath_Divide=intNumber3
End Function

'Code to be written in the Form_Load event of StandardExe for mentioned below
Private Sub Form_Load()
Dim Math as IMath
Dim Addition as Add
Dim Subtraction as Subtract
Dim Multiplication as Multiply
Dim Divison as Divide
Set Addition=New Add
'Assigning the reference of Add class to base class IMath object
Set Math=Addition
debug.print Math.Add(10,10)
Set Subtraction=New Subtract
'Assigning the reference of Subtract class to base class IMath object
Set Math=Subtraction
debug.print Math.Subtract(10,10)
Set Multiplication=New Multiply
'Assigning the reference of Multiply class to base class IMath object
Set Math=Multiplication
debug.print Math.Multiply(10,10)
Set Divison=new Divide
'Assigning the reference of Divide class to base class IMath object
Set Math=Divison
debug.print Math.divide(10,10)
End Sub

-by Invincible(psycho@nepalimail.com)