#include <stdio.h>
void pr(int digits, float value)
{
        printf("%6.*f\n", digits, value);
}

int main()
{
        pr(4, 1.2345f);
        pr(3, 12.345f);
        pr(2, 123.45f);
}

        printf("F = %6.*f Hz\n", value < 10 ? 4 : value < 100 ? 3 : 2, value);

    fprintf_P(fconsole
        , value < 10 ? PSTR("F = %6.4f Hz\n") : value < 100 ? PSTR("F = %6.3f Hz\n") : PSTR("F = %6.2f Hz\n")
        , value);

#define F_CPU 8000000UL // 16.0 MHz
#include <util/delay.h>
#include "defines.h"
#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <avr/pgmspace.h>
#include "lcd.h"

volatile unsigned char q;
volatile unsigned int f=0xF;
volatile double frq;
double fp = 1;
FILE lcd_str = FDEV_SETUP_STREAM(lcd_putchar, NULL, _FDEV_SETUP_WRITE);

ISR(TIMER0_OVF_vect)
{
++q;
if(q==1)
    {
    PORTA ^= (1<<7);
    q=0;
    }
}

int main(void)
{
DDRA  = 0b10000000;
PORTB = 0b00000000;
DDRB  = 0b10111111;
TCCR0A = 0b10000000;
TCCR0B = 0b00000110;
TIMSK  = 0b00000010;

frq=123;

lcd_init();
stderr = &lcd_str;


fprintf_P(stderr, PSTR("F = %6.4f Hz\n"), frq);

/*value < 10 ? PSTR("F = %6.4f Hz\n") : value < 100 ? PSTR("F = %6.3f Hz\n") : PSTR("F = %6.2f Hz\n")*/

asm("sei");

    while(1)
        {
        
        asm("nop");
        }

return 0;
}

   float pi = 3.14f;
   printf("pi = %.02f\n", pi);

pi = 3.14

dtostrf(f, WIDTH, PREC, buff)

../exampl.c:44: warning: format '%.02f' expects type 'double', but argument 2 has type 'float'

  printf(stderr, "pi = %.02f\n", pi);