declaration for sending to the serial port

Why when i use serial port i need to declare this 2 declaration

#ifdef MONITOR51                           // Debugging with Monitor-51 needs
char code reserve [3] _at_ 0x23;         // space for serial interrupt if
#endif 
                                 // Stop Exection with Serial Intr.
#ifndef MONITOR51
  SCON  = 0x50;               // SCON: mode 1, 8-bit UART, enable rcvr
  TMOD |= 0x20;               // TMOD: timer 1, mode 2, 8-bit reload
  TH1   = 221;                // TH1:  reload value for 1200 baud @ 16MHz
  TR1   = 1;                  // TR1:  timer 1 run
  TI    = 1;                  // TI:   set TI to send first char of UART
#endif

.
What is good for ???
Why can i just write this :

  SCON  = 0x50;               // SCON: mode 1, 8-bit UART, enable rcvr
  TMOD |= 0x20;               // TMOD: timer 1, mode 2, 8-bit reload
  TH1   = 221;                // TH1:  reload value for 1200 baud @ 16MHz
  TR1   = 1;                  // TR1:  timer 1 run
  TI    = 1;                  // TI:   set TI to send first char of UART

What is the different between them ???

Thanks for the help

Mayer