#include<iostream>
void main()
{
    int month=1;
        char *season=NULL;
        switch(month){
        case 12:
        case 1:
        case 2:
            season="winter";
            break;
        case 3:
        case 4:
        case 5:
            season="spring";
            break;
        case 6:
        case 7:
        case 8:
            season="summer";
            break;
        case 9:
        case 10:
        case 11:
            season="autumn";
            break;
        printf("april is in the %s\n " ,season);
        default:
            printf("bog month");
            
        }
        
}

.........

#include<stdio.h>
int main()    //不建议用void main
{
    int month=1;
        char *season=NULL;
        switch(month){
        case 12:
        case 1:
        case 2:
            season="winter";
            break;
        case 3:
        case 4:
        case 5:
            season="spring";
            break;
        case 6:
        case 7:
        case 8:
            season="summer";
            break;
        case 9:
        case 10:
        case 11:
            season="autumn";
            break;
        default:
            printf("bog month");
            
        }
        printf("april is in the %s\n " ,season);    //放这就ok了
        return 0;
}
因为你那个版本的printf("april is in the %s\n " ,season);这句是不会被执行的