Determinate times between operations

Determinate-times.c

#include <stdio.h>
#include <sys/time.h>
//#include <rand.h>

/* Funcion prototipo */
double tiempos(struct timeval , struct timeval );

/* Funcion principal */
int main(){
  int x;
  struct timeval T_START, t_end;

  // Get first time
  gettimeofday(&T_START , NULL );
  /* ...Do somethingo... */
  printf("Insert a number \n>");
  scanf("%d",&x);
  // Get second time
  gettimeofday(&t_end , NULL );
  printf("%f seconds\n", tiempos(T_START, t_end));
  return 0;
}

/* Implementacion de funciones */
 
double tiempos(struct timeval inicio, struct timeval fin){

  double  mil_time, sec_time , usec_time;

  sec_time = fin.tv_sec - inicio.tv_sec;
  usec_time = fin.tv_usec - inicio.tv_usec;
  mil_time = ((1000*sec_time)+(usec_time/1000.0))+0.5;
  // Returns the value in seconds
  return mil_time/1000.0;
}