Check my C code for PIC16F877 which is used in car security system

//Preprocessor
#INCLUDE <16F877.H>
#FUSES HS,NOWDT,NOLVP
#USE DELAY(clock=12000000)
#USE RS232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

//Define pin
#DEFINE SIREN     PIN_B5
#DEFINE CL1   PIN_B4
#DEFINE CL2       PIN_B3
#DEFINE ULTRA   PIN_A0
#DEFINE TOUCH     PIN_A1
#DEFINE LIGHT     PIN_A2
#DEFINE DOOR      PIN_A3
#DEFINE REMOTE  PIN_A4

//Global declaration
int A,B,C,D,RC,EN;
int RC1[2];
char SENSOR1, SENSOR2, SENSOR3, SENSOR4, SENSOR5, TEMP;
char P[4];
char S[51];

//Sound siren
void SIREN_ON()
{
   OUTPUT_HIGH(SIREN);
   DISABLE_INTERRUPTS(INT_RTCC);
}
//Unlock doors
void UNLOCK()
{
   OUTPUT_HIGH(CL1);
   OUTPUT_LOW(CL2);
}
//Lock doors
void LOCK()
{
   OUTPUT_LOW(CL1);
   OUTPUT_HIGH(CL2);
}

//Ultrasonic sensor triggered
void SEND_CALL1()
{
   PRINTF("ATD0123456789;\n\r");
}
//Touch sensor triggered
void SEND_CALL2()
{
   PRINTF("ATD0123456789;\n\r");   
}
//Light sensor triggered
void SEND_CALL3()
{
   PRINTF("ATD0123456789;\n\r");
}
//Door sensor triggered
void SEND_cALL4()
{
   PRINTF("ATD0123456789;\n\r");
}
//Central lock triggered
void SEND_CALL5()
{
   PRINTF("ATD0123456789;\n\r");
}




#INT_RTCC
T0()
{
      SENSOR1=INPUT(ULTRA);
      SENSOR2=INPUT(TOUCH);
      SENSOR3=INPUT(LIGHT);
      SENSOR4=INPUT(DOOR);
      SENSOR5=INPUT(CL1);
   if(SENSOR1)
      {
         SEND_CALL1();
         SIREN_ON();
      }
      else if(SENSOR2)
      {
         SEND_CALL2();
         SIREN_ON();
      }
      else if(SENSOR3)
      {
         SEND_CALL3();
         SIREN_ON();
      }
      else if(SENSOR4)
      {
         SEND_CALL4();
         SIREN_ON();
      }
   else if(SENSOR5)
   {
      SEND_CALL5();
      SIREN_ON();
   }
}

#INT_RDA
SERIAL()
{
   //Optional   
   if(kbhit())
   {
      TEMP=GETC();
      if(A<50)
      {
         S[A]=TEMP;
         A++;
      }
      else
      {
         A=0;
         S[A]=TEMP;
         A++;
      }
   }
   DELAY_MS(100);
   return A,S;
}

//Main function
void MAIN()
{
   
     SET_RTCC(0);
     SETUP_COUNTERS(RTCC_INTERNAL,RTCC_DIV_64);
   EXT_INT_EDGE(0,H_TO_L);     
   ENABLE_INTERRUPTS(INT_EXT);
     ENABLE_INTERRUPTS(INT_RDA);
    ENABLE_INTERRUPTS(GLOBAL);
    ENABLE_INTERRUPTS(INT_RTCC);
     SET_TRIS_A(0x3F);
     SET_TRIS_B(0x01);
   //SET_TRIS_C(0x0F);
   SET_TRIS_D(0x00);

     DELAY_MS(5000);

   PRINTF("\n\rATZ\n\r");
   DELAY_MS(500);
     PRINTF("\n\rAT\n\r");
   DELAY_MS(500);
   PRINTF("\n\rAT+CNMI=2,3,0,0,0\n\r");
   DELAY_MS(500);
   
   SENSOR1==0;
     SENSOR2==0;
     SENSOR3==0;
     SENSOR4==0;
     SENSOR5==0;
   A=0;
   B=0;
   C=0;
   D=0;
   EN=0;
     RC=0;
     UNLOCK();

}