In this session we were introduced to “class” which is one of the most important significance of Object Oriented Programming.

#1.Problem statement:

We have to find the area of a rectangle using class of an Object Oriented Program.

Solution:

#include<iostream.h> #include<stdio.h> #include<conio.h> #include<math.h> class area{ private: float x1,y1,x2,y2,x3,y3,x4,y4; float a,b,c; public: float input(); float output(); }p; float area::input(){ cout<<"enter points: A, B, C & D”; cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4; a=0.5*((x1*(y2-y3))-(x2*(y3-y1))+(x3*(y1-y2))); b=0.5*((x1*(y3-y4))-(x3*(y4-y1))+(x4*(y1-y3))); c=sqrt(a*a)+sqrt(b*b); return c; } float area::output(){ cout<<"result="<<input(); } void main(){ clrscr(); p.output(); getch(); }

Class Diagram:

Class area

Private:      x1,y1,x2,y2,x3,y3,x4,y4      a,b,c

Public:      Input()      Output()

Remarks:

Here we calculated the area by summing area of two triangles formed by the points.

#2. Problem statement:

We have to calculate the area of a given rectangle by drawing perpendicular on the joining line of two opposite points.

Solution:

#include<iostream.h> #include<stdio.h> #include<conio.h> #include<math.h> class area{ private: float x1,y1,x2,y2,x3,y3,x4,y4; float a,b,c,d,x,h; public: float input(); void output(); }p; float area::input(){ cout<<"enter points: A, B, C & D”; cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4; b=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)); a=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3)); c=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2)); x=(a*a+c*c-b*b)/(2*c); h=sqrt((a*a)-(x*x)); d=c*h; return d; } void area::output(){ cout<<"result="<<input(); } void main() { clrscr(); p.output(); getch(); }

Class Diagram:

Class area

Private:      x1,y1,x2,y2,x3,y3,x4,y4      a,b,c,d,x,h

Public:      Input()      Output()

Remark:

We used Pythagoras’s law here & doubled area of a triangle to get the required area. 

I had problem with the function input(). If I use it in main() function it get executed twice.but if I use it through output() then it gets the required result. Other than that this session was quite good.