<C Primer Plus>8 The if statement

 1 #include <stdio.h>
 2 #include <math.h>
 3 int main(void){
 4     const int FREESEING = 0;
 5     float temperature;
 6     int cold_days = 0;
 7     int all_days = 0;
 8 
 9     printf("Please input the temperature:
");
10     printf("q is quit.
");
11     while (1 == scanf("%f", &temperature)){
12         all_days++;
13         if (temperature < FREESEING){
14             cold_days++;
15         }
16     }
17     if (all_days != 0){
18         printf("The number of all_days = :%d ", all_days);
19         printf("The cold day = %d 
", cold_days);
20         printf("the cold day %.2f%% of all day.
", 100.0*(float)cold_days / all_days);
21     }
22     else{
23         printf("input no data.
");
24     }
25 
26     return 0;
27 }
if (expression)
　　statement