Program to Draw a Line using DDA Algorithm - CG

Program :

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

void lineDDA(int, int, int, int);

void main()
{

    int x1, y1, xn, yn;
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "");

    printf("Enter the starting coordinates of line: ");
    scanf("%d %d", &x1, &y1);

    printf("Enter the ending coordinates of line: ");
    scanf("%d %d", &xn, &yn);

    lineDDA(x1, y1, xn, yn);
    getch();
}

void lineDDA(int x1, int y1, int xn, int yn)
{

    int dx, dy, m, i;
    m = (yn-y1)/(xn-x1);

    for (i=x1; i<=xn; i++)
    {
        if (m <= 1)
        {
            dx = 1;
            dy = m * dx;
        }
        else
       {
           dy = 1;
           dx = dy / m;
       }

x1 = x1 + dx;
y1 = y1 + dy;

putpixel(x1, y1, RED);

delay(20);
}