C program for dda algorithm. DDA (Digital Differential Analyzer) Algorithm also know as Vector Generation algorithm.

**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();
}
```

**Output :**

**DDA algorithm :**

- Define the nodes, i.e end points in form of (x1,y1) and (x2,y2).
- Calculate the distance between the two end points vertically and horizontally, i.e dx=|x1-x2| and dy=|y1-y2|.
- Define new variable name ‘pixel’, and compare dx and dy values,

if dx > dy then

pixel=dx

else

pixel =dy. - dx=dx/pixel

and dy=dy/pixel - x=x1;

y=y1; - while (i<=pixel) compute the pixel and plot the pixel with x=x+dx and y=y+dy.

If you are having any problem related to the post, do comment below.

Why didn’t you do the rounding in this program?

It showing an error that GRAPHICS.H is No such file or directory.

without rounding off would it work successfully ??

the principle of digital differential analyzer is it rounding off the point which contain a fractional value, for which it takes more time to calculate and can’t able draw the original line.