I am new to the avr (8bit uc) and recently I ran into a problem using serial communication (uart) with PC. Microcontroller fails to responsd in putty terminal where it should echo back whatever I have sent.

Thank you for your response everyone .

I am sorry for the corrupt code I had no idea what I was doing since I am newbie to this code indention in stack exchange.

The new code is attached below please kindly suggest

#define F_CPU 16000000UL
#include <avr/io.h>
#include <avr/interrupt.h>

volatile char data;

void USARTInit(uint16_t ubrr_value) {
    UBRRL = ubrr_value;
    UBRRH = (ubrr_value >> 8);
    UCSRC = (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);
    UCSRB = (1 << RXEN) | (1 << TXEN);
}

void USARTWriteChar(char data) {
    while (!(UCSRA & (1 << UDRE)))
        { }

    //Now write the data to USART buffer
    UDR = data;                                                               
}                                                                             
                                                                              
void main() {                                                                 
    sei();                                                                    
    UCSRB |= (1 << RXCIE);                                                    
    USARTInit(51);                                                            
                                                                              
    while (1) {                                                               
        if (data == 'a') {                                                    
            USARTWriteChar(data);
        }
    }
}

ISR(USARTRXC_vect) {
    data = UDR;
}

so here foo just represents my data='a', unfortunately avr is not responding to my inputs . when I type "a" .