Why DDA algorithm ?

DDA Algorithm is used to plot line between two nodes i.e two end points in computer system.
While our computer understand pixels, if we want to plot a line, we should have maximum intermediate vertices of the line i.e intermediate points, so as to generate a straight line. Here DDA does the same.

c program for dda algorithm :

‪#‎include‬ <graphics.h>
#include <stdio.h>
#include <math.h>

int main( )
{
float x,y,x1,y1,x2,y2,dx,dy,pixel;
int i,gd,gm;

printf("Enter the value of x1 : ");
scanf("%f",&x1);
printf("Enter the value of y1 : ");
scanf("%f",&y1);
printf("Enter the value of x2 : ");
scanf("%f",&x2);
printf("Enter the value of y1 : ");
scanf("%f",&y2);

detectgraph(&gd,&gm);
initgraph(&gd,&gm,"");

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

if(dx>=dy)
pixel=dx;
else
pixel=dy;

dx=dx/pixel;
dy=dy/pixel;

x=x1;
y=y1;

i=1;
while(i<=pixel)
{
putpixel(x,y,1);
x=x+dx;
y=y+dy;
i=i+1;
delay(100);
}
getch();
closegraph();
}