Bisection method

/* Write a Program to solve equation using Bisection Method */
#include
float bisection(float,float,float);
void main()
{
  float xl,xu,ea,fxr;
  clrscr();
  printf("Enter Lower Bound : ");
  scanf("%f",&xl);
  printf("Enter Upper Bound : ");
  scanf("%f",&xu);
  printf("Enter Percentage Error : ");
  scanf("%f",&ea);
  fxr = bisection(xl,xu,ea);
  printf("F(xr) : %.2f",fxr);
 getch();
}

float bisection(float xl,float xu,float ea)
{
  float xr,fxr,tmp;
  do
   {
     xr = (xl + xu) / 2;
     fxr = ((xr*xr*xr) -9 * xr + 1);

     if(fxr*xu < 0)
        xu = xr;
     else if(fxr*xu>0)
        xl = xr;
     else
         xr = 0;

      if(fxr<0)
       tmp = fxr * -1;
   }while(tmp>ea);
  return xr;
 }