Program to draw a line using Cartesian Slope-Intercept Equation

 # include <iostream.h>
 # include <graphics.h>
 # include    <conio.h>
 # include     <math.h>

 void show_screen( );

 void slope_intercept_line(const int,const int,const int,const int);


 int main( )
    {
       int driver=VGA;
       int mode=VGAHI;

       int x_1=0;
       int y_1=0;

       int x_2=0;
       int y_2=0;

       do
      {
         show_screen( );

         gotoxy(8,10);
         cout<<\"Coordinates of Point-I (x1,y1) :\";

         gotoxy(8,11);
         cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

         gotoxy(12,13);
         cout<<\"Enter the value of x1 = \";
         cin>>x_1;

         gotoxy(12,14);
         cout<<\"Enter the value of y1 = \";
         cin>>y_1;

         gotoxy(8,18);
         cout<<\"Coordinates of Point-II (x2,y2) :\";

         gotoxy(8,19);
         cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

         gotoxy(12,21);
         cout<<\"Enter the value of x2 = \";
         cin>>x_2;

         gotoxy(12,22);
         cout<<\"Enter the value of y2 = \";
         cin>>y_2;

         initgraph(&driver,&mode,\"..\\\\Bgi\");

         setcolor(15);
           slope_intercept_line(x_1,y_1,x_2,y_2);

         setcolor(15);
           outtextxy(110,460,\"Press <Enter> to continue or any other key to exit.\");

         int key=int(getch( ));

         if(key!=13)
        break;
      }
       while(1);

       return 0;
    }



 //------------------------  Funcion Definitions  ------------------------//




 //------------------------  slope_intercept_line( )  --------------------//


 void slope_intercept_line(const int x_1,const int y_1,
                        const int x_2,const int y_2)
    {
       int color=getcolor( );

       if(x_1!=x_2)
      {
         float x=x_1;
         float y=y_1;

         float dx=(x_2-x_1);
         float dy=(y_2-y_1);

         float m=(dy/dx);
         float b=(y-(m*x));

         if(abs(dx)>=abs(dy))
        {
           float x_inc=((x_2>=x_1)?1:-1);

           putpixel(x,y,color);

           while((int)(x+0.5)!=x_2)
              {
             x+=x_inc;
             y=((m*x)+b);

             putpixel((int)(x+0.5),(int)(y+0.5),color);
              }
        }

         else
        {
           float y_inc=((y_2>=y_1)?1:-1);

           putpixel(x,y,15);

           while((int)(y+0.5)!=y_2)
              {
             y+=y_inc;
             x=((1/m)*(y-b));

             putpixel((int)(x+0.5),(int)(y+0.5),color);
              }
        }
      }

       else
      {
         int x=x_1;
         int y=y_1;

         int y_inc=((y_2>=y_1)?1:-1);

         putpixel(x,y,color);

         while(y!=y_2)
        {
           y+=y_inc;

           putpixel(x,y,color);
        }
      }
    }


 //--------------------------  show_screen( )  ---------------------------//


 void show_screen( )
    {
       restorecrtmode( );
       textmode(C4350);

       cprintf(\"\\n********************************************************************************\");
       cprintf(\"********************-                                      -********************\");
       cprintf(\"*-------------------- \");

       textbackground(1);
       cprintf(\" Cartesian Slope Intercept Equation \");
       textbackground(8);

       cprintf(\" --------------------*\");
       cprintf(\"*-******************-                                      -******************-*\");
       cprintf(\"*-****************************************************************************-*\");

       for(int count=0;count<42;count++)
      cprintf(\"*-*                                                                          *-*\");

       gotoxy(1,46);
       cprintf(\"*-****************************************************************************-*\");
       cprintf(\"*------------------------------------------------------------------------------*\");
       cprintf(\"********************************************************************************\");

       gotoxy(1,2);
    }