Program to Draw Line using DDA Algorithm in C

#include <stdio.h>
#include <conio.h>
#include <graphics.h>
void DDA(int, int, int, int);
void main()
{
    int x1, y1, xn, yn;
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "C:\\TC\\BGI");
    printf("Enter the starting coordinates of line: ");
    scanf("%d %d", &x1, &y1);
    printf("Enter the ending coordinates of line: ");
    scanf("%d %d", &xn, &yn);
    DDA(x1, y1, xn, yn);
    getch();
}
void DDA(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, 10);
delay(50);
}
}