kick- starting technique for interrupt driven

Hello everyone. I'm doing a RTOS project, about using kick- starting technique for interrupt driven (UART). i using KeilC 4, and mu code:

#include <REGX51.H>

#define MAX 50
typedef enum { FALSE = 0, TRUE  = !FALSE } bool;
bool coban;

struct QueueRecord;
typedef struct QueueRecord *Queue;
void MakeEmpty( Queue Q );
int IsEmpty( Queue Q );
int IsFull( Queue Q );
CreateQueue( int MaxElements );
int Enqueue( char  ItemIn, Queue Q );
int Dequeue(  Queue Q  );

void UART_init();
void UART_putchar(char ch);
char UART_get_byte(void);

void SendDataProcedure();

/***************ISR************/


void serial() interrupt 4 {
        if (RI == 1){    /* ngat nhan da xay ra  */
                RI = 0;
                UART_get_byte();
                Enqueue( SBUF );
                if(coban == FALSE ) SendDataProcedure();
        }
        else{
                if (TI == 1){
                        TI = 0;
                        coban = 0;
                        SendDataProcedure();
                }
        }
}
/**************OUTPUT ROUTINE***********/
void SendDataProcedure(){

        char ch;
        if (!IsEmpty()){
                Dequeue (&ch);
                SBUF = ch;
                coban = TRUE;
        }
        else return();

}

/***************QUEUE***************/
typedef struct QueueRecord
        {
        char Array[MAX];
            int Capacity;
            int Front;
            int Rear;
            int Size;

        };



 void MakeEmpty( Queue Q )
        {
            Q->Size = 0;
            Q->Front = 0;
            Q->Rear = 0;
        }



 int IsEmpty( Queue Q )
        {
            return Q->Size == 0;
        }


 int IsFull( Queue Q )
        {
            return Q->Size == Q->Capacity;
        }


 CreateQueue( int MaxElements )
{
        Queue Q;
        Q->Capacity = MaxElements;
        MakeEmpty( Q );
        return Q;
}


int Enqueue( char  ItemIn, Queue Q ){
    if (Q->Rear==MAX-1 )
        Q->Rear=0;
    else
        (Q->Rear)++;
    Q->Array[ Q->Rear ] = ItemIn;
}



int Dequeue( Queue Q )
        {
           // if( IsEmpty( Q ) )return 0;
                //              else {
                                        if (Q->Front ==MAX-1)
                                                Q->Front=0;
                                        else
                                                Q->Front++;

                        return(Q->Array[Q->Front]);
         }



/************* UART*******************/


void UART_init()
{
        SCON = 0x50;    // Enable UART set by timer1
        TMOD = 0x20;    //Timer1 che do 2 tu nap lai
        TH1 = 0xFD;             // baurate = 9600
        TR1 = 1;                //khoi dong timer1
        IE = 0x91;              // cho phep cac ngat xay ra

}



void UART_putchar(char ch)
{
        SBUF = ch;
        while(!TI);
        TI = 0;
}

char UART_get_byte(void)
{

        return SBUF;
}



/*****************MAIN***************/
void main(){

        CreateQueue( 8 );
        UART_init();
        coban = TRUE;
        UART_putchar ("tu");
}

but KeilC annouce that error "Kickstart.c(30): error C100: unprintable character 0xEC skipped" for the line i BOLDed

Please help me, thank alot