K&R-2-1.c

float fl, fltest, last;
fl = 0.0;   // check if the float number is NaN

while(fl == 0.0) {
    	last = fltest;
    	fltest += 1.111e+31;    // sign bit 1 + exponent 8 bits + mantissa 23 bits
        
    	if((fl = (fl + fltest) + (-fltest)) != 0.0) {           // 0.0 +∞ + (-∞) == NaN
            break; 
    	}
}

printf("Unsigned float max: %e", last);