第92行的if（sign==0）怎么定义他呀！求解

#include<reg51.h>
#include<reg51.h>
#define uchar unsigned char

#define TX_ADR_WIDTH 5
#define TX_PLOAD_WIDTH 4
#define LED P0
unsigned char code message_number[]={"AT+CMGS="15718070982""};
unsigned char code message_content[]={"someone is coming ! --FROM BOBO"};
uchar code TX_ADDRESS[TX_ADR_WIDTH]={0x34,0x43,0x10,0x10,0x01};

uchar RX_BUF[TX_PLOAD_WIDTH];
uchar TX_BUF[TX_PLOAD_WIDTH];
uchar flag;
uchar DATA=0x01;
uchar bdata sta;
sbit RX_DR=sta^6;
sbit TX_DS=sta^5;
sbit MAX_RT=sta^4;
sbit led1=P1^0;
sbit led2=P1^1;
sbit spk=P1^6;
sbit rx=P3^0;
sbit tx=P3^1;
sbit i0=P3^2;
sbit i1=P3^3;
sbit l1=P1^2;
sbit l2=P1^3;
sbit l3=P1^4;
sbit l4=P1^5;
sbit l5=P1^7;

void main(void)
{

if(i1==0)
{     led1=1;
   led2=1;
     l1=1;
     l2=1;
     spk=0;
     l3=0;
     l4=0;
     l5=0;
     rx=0;
     tx=0;
    
} 
else
     if(i0==0)
     { led1=0;
       led2=0;
           l1=0;
         l2=0;
           spk=1;
           l3=1;
         l4=1;
         l5=1;
           rx=1;
           tx=1;
     }
     else
     {     led1=1;
       led2=1;
           l1=1;
         l2=1;
         spk=0;
           l3=0;
         l4=0;
         l5=0;
         rx=0;
         tx=0;
     }   
return;

}

void send(uchar *tab)

{
while((*tab)!='\0')
{
SBUF=*tab;
while(T1==0)
T1=0;
tab++;
}
}
void ext0() interrupt 0
{
EA=1;
EX0=1;
IT0=1;
If(sign==0);
{
TR0=1;
TR1=1;
delay_ms(500);
led=0;
flag=1;
}
}
void T0_Count() interrupt 1
{
if(sign==0)
TR1=1;
else
TR1=0;
TH0=(65535-20000)/256;
TL0=(65535-20000)%256;
Time_Count++;
if(Time_Count==20)
{
Time_Count=0;
led=!led;
beep=!beep;
flag=1;
}
}
void long_delay(unsigned int cnt)
{
unsigned int k=50000;
while(--cnt)
{
while(k--);
}
}
void serial_init(viod)
{
SCON=0x50;
TMOD=0x20;
TH1=0xfd;
TL1=0xfd;
TR1=1;
EA=1;
ES=1;
}

void Send_Message(void)
{
Print_S(message_number);
send_hex(0x0d);
long_delay(2);
Print_S(message_content);
send_hex(0x0d);
long_delay(2);
send_hex(0x1a);
long_delay(1);
}
viod STOP(viod)
{ if(!(P3&Ox01))
{
TX_BUF[0]=DATA;
Check_ACK(1);
delay_ms(250);
delay_ms(250);
LED=0xff;
beep=1;
while(!(P3&0x01))
DATA<<=1;
if(!DATA)
DATA=0x01;
}
}