iterate()
    {
      for(year=config->firstyear-config->nspinup;year<=config->lastyear;year++) {
        co2=getco2();
        getclimate();
        if(landuse) getlanduse(); /* reads landuse data for specific year, cft frac and irrigation frac*/
        if(wateruse) getwateruse();
        if(config->river_routing) iterateyear_river(); else iterateyear(); /* one year over all grid cells */
    
        flux_sum();
        if(year==config.restartyear) fwriterestart();
      }
    }

    iterateyear()
    {
      for(cell=0;cell<config.ngridcell;cell++) {
        init_annual();
        foreachmonth(month) {
          foreachdayofmonth(dayofmonth,month) 
           update_daily(); /* daily update of individual cell ? foreachstand() ? daily_stand() is a makro expansion which applies different functions for different standtypes, it calls daily_natural, daily_agriculture, ... */
          update_monthly();
        }
        update_annual();
      }
    }