# Program to draw a line using Digital Differential Analyzer (DDA) Algorithm

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

void show_screen( );

void dda_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);
dda_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;
}

//-----------------------------  dda_line( )  ---------------------------//

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

int x1=x_1;
int y1=y_1;

int x2=x_2;
int y2=y_2;

if(x_1>x_2)
{
x1=x_2;
y1=y_2;

x2=x_1;
y2=y_1;
}

float dx=(x2-x1);
float dy=(y2-y1);

int steps=abs(dy);

if(abs(dx)>abs(dy))
steps=abs(dx);

float x_inc=(dx/(float)steps);
float y_inc=(dy/(float)steps);

float x=x1;
float y=y1;

putpixel(x,y,color);

for(int count=1;count<=steps;count++)
{
x+=x_inc;
y+=y_inc;

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

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

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

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

textbackground(1);
cprintf(\" Digital Differential Analyzer Algorithm \");
textbackground(8);

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

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

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

gotoxy(1,2);
}
```

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