DDA Line Drawing Algorithm

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

void main() 
{ 

    int gd=DETECT,gm=DETECT,s,dx,dy,m,x1,y1,x2,y2; 
    float xi,yi,x,y; 

    clrscr(); 

    printf("Enter the sarting point x1 & y1n"); 
    scanf("%d%d",&x1,&y1); 

    printf("Enter the end point x2 & y2n"); 
    scanf("%d%d",&x2,&y2); 

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

    dx=x2-x1; 
    dy=y2-y1; 

    if(abs(dx)>abs(dy)) 
        s=abs(dx); 
    else 
        s=abs(dy); 

    xi=dx/(float)s; 
    yi=dy/(float)s; 

    x=x1; 
    y=y1; 

    putpixel(x1,y1,4); 

    for(m=0; m < s; m++) 
    { 
        x+=xi; 
        y+=yi; 
        putpixel(x,y,4); 
    } 
    getch(); 
}