Thread: Error in Line - 4 " ) Expected"

I use the Turbo C++ 3.0 to run this C program with the file name DDA.C. In line 4 it gives the error " ) Expected". Please tell me whats wrong with my code. I am trying to implement DDA Algorithm. ro function is being used to roundoff a number.

Code:

#include<conio.h>
#include<graphics.h>
#include<stdio.h>
void ro(float &x)
{
    float ret=x,t=x;
    ret=ret*10;
    t=t*10;
    ret=ret-t;
    if(ret<5.0)
    {
        x*10;
        x-ret;
        x/10;
    }
    else if(ret>=5.0)
    {
        x*10;
        x-ret;
        x=x+1;
        x/10;
    }
};
void main()
{
    int gd=DETECT,gm,x1,i,x2,y1,y2,dy,dx;
    float m,temp;
    clrscr();
    printf("\n\tEnter Two Co-ordinates");
    printf("\n\n\tX1: ");
    scanf("%d",&x1);
    printf("\n\tY1: ");
    scanf("%d",&y1);
    printf("\n\tX2: ");
    scanf("%d",&x2);
    printf("\n\tY2: ");
    scanf("%d",&y2);
    initgraph(&gd,&gm,"C:\\TC\\BGI");
    clrscr();
    dy=y2-y1;
    dx=x2-x1;
    m=dy/dx;
    if(dy>dx)
    {
        for(i=y1;i<=y2;i++)
        {
            temp=x1;
            putpixel(ro(&temp),i,WHITE);
            temp=temp+m;
        }
    }
    getch();
}