#include <avr/io.h>          
  
  void transmit (unsigned char data);
  
  int main (void)
  {
      unsigned char ch ;
    
      ucsrb = (1<<txen)|(1<<rxen) ;                      
      ucsrc = (1<< ucsz1)|(1<<ucsz0)|(1<<ursel);
      ubrrl = 0x33 ;
  
      while(1)
      {
        while(!(ucsra&(1<<rxc)));   
      
      ch = udr ;
      
      if (ch >= 'a' && ch <= 'z')
        {
            ch += ('a'-'a');
            
        while (! (ucsra & (1<<udre)));
            
        udr = ch ;
        }
      }
  
    return 0 ;
  }