ATMega8 interrupt mode UART test program

#include
#include
#include

#define uchar unsigned char
#define uint unsigned int

uchar g_bTxdPos=0; //Send positioning counter

uchar g_bTxdLen=0; //Waiting for the number of bytes to be sent
uchar g_bRxdPos=0; //Receive positioning counter
uchar g_bRxdLen=0; //Waiting for the number of bytes to be received

uchar g_aSendBuf[16]; //Send data buffer
uchar g_aRecvBuf[16]; //Receive data buffer

//Receive interrupt
SIGNAL (SIG_ UART _RECV)
{
    uchar c=UDR; 
    if(g_bRxdLen>0)
    {
        g_aRecvBuf[g_bRxdPos++]=c;
        g_bRxdLen--;
    }
}

//Send interrupt
SIGNAL (SIG_UART_TRANS)
{
    if(--g_bTxdLen>0)
        UDR=g_aSendBuf[++g_bTxdPos];
}

//Is reception completed
uchar IsRecvComplete(void)
{
    return g_bRxdLen==0;
}

//Send data of specified length from send buffer
void SendToUart(uchar size)
{
    g_bTxdPos=0;
    g_bTxdLen=size;
    UDR=g_aSendBuf[0];
    while(g_bTxdLen>0);
}

//Receive data of specified length to receive buffer
void RecvFromUart(uchar size,uchar bwait)
{
    g_bRxdPos=0;
    g_bRxdLen=size;
    if(bwait)
        while(g_bRxdLen>0);
}

int main( void )
{
    uchar i;

  //uart initialization
    //receive enable, transmit enable, receive interrupt enable, transmit interrupt enable
    UCSRB=(1<    UBRRL=25; // baud=9600 UBRR=CK/(baud*16) -1   

    sei();//Total interrupt enabledwhile
    
    (1)
    {
        //Asynchronously receive 16 bytes of dataRecvFromUart
        (16,0);

        //Wait for reception to completewhile
        (!IsRecvComplete());
        
        //Copy the received data to the send bufferfor
        (i=0;i<16;i++)
              g_aSendBuf=g_aRecvBuf;
        
        //Send back the received dataSendToUart
        (16);
    }
}