working with atmega16

//Program for ADC to read from channel 0 and show the 8 bit o/p on PORTB
 
#include<avr/io.h>
#include<util/delay.h>
 
void ADC_init(void);
unsigned int ADC_read(unsigned char);
 
// ------------------------------------------------
int main(void)
{
unsigned int value;
DDRB=0xFF;
DDRD=0x03;
ADC_init(); // Initialization of ADC
// ch=0;
while(1)
{
value=ADC_read(0);
PORTB=value;
_delay_ms(500);
} 
}
//------------------------------------------------
 
void ADC_init(void) // Initialization of ADC
{
ADMUX=(1<<REFS0); // AVcc with external capacitor at AREF
ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);
// Enable ADC and set Prescaler division factor as 128
}
 
unsigned int ADC_read(unsigned char ch)
{
ch= ch & 0b00000111; // channel must be b/w 0 to 7
ADMUX |= ch; // selecting channel
 
ADCSRA|=(1<<ADSC); // start conversion
while(!(ADCSRA & (1<<ADIF))); // waiting for ADIF, conversion complete
ADCSRA|=(1<<ADIF); // clearing of ADIF, it is done by writing 1 to it
 
return (ADC);
}