#include <avr/io.h>

uint8_t csb = 1;             // Clock select bits uint8_t 
uint8_t ocrval = 255/4;      // Output Compare register vaule



int main() 

{ 
// Set TCCR0 in the Fast PWM mode 
TCCR0 =(1 << WGM01) | (1 << WGM00) | (1 << COM01) | csb; 
OCR0 = ocrval; 
TCNT0 = 0; 
DDRB |= (1 << PB3); // Set PB3(OC0) as output 
}