程序代码：

#include<stdio.h>
void add(int a1, int a2){
    int resa = a1 + a2;
    printf("%d\n", resa);
    printf("done!\n");
}
void sub(int s1, int s2){
    int ress = s1 - s2;
    printf("%d\n", ress);
    printf("done!\n");
}
void mul(int m1, int m2){
    int resm = m1*m2;
    printf("%d\n", resm);
    printf("done!\n");
}
void div(int d1, int d2){
    int resd = d1 / d2;
    printf("%d\n", resd);
    printf("done!\n");
}


int main(){
    printf("Enter the operation of your choice!\n");
    printf("a.add  s.substract  m.multiply  d.diveide q.quit\n");
    char choice;
    while ((choice = getchar()) != 'q'){
        switch (choice){
        case'a':
            int a1, a2;
            printf("please enter a1:\n");
            scanf_s("%d", &a1);
            printf("please enter a2:\n");
            scanf_s("%d", &a2);
            add(a1,a2);
            break;
        case 's':
            int s1, s2;
            printf("please enter s1:\n");
            scanf_s("%d", &s1);
            printf("please enter s2:\n");
            scanf_s("%d", &s2);
            sub(s1, s2);
            break;
        case 'm':
            int m1, m2;
            printf("please enter m1:\n");
            scanf_s("%d", &m1);
            printf("please enter m2:\n");
            scanf_s("%d", &m2);
            mul(m1, m2);
            break;
        case 'd':
            int d1, d2;
            printf("please enter d1:\n");
            scanf_s("%d", &d1);
            printf("please enter d2:\n");
        gtd1:
            scanf_s("%d", &d2);
            if (d2 != 0)
                div(d1, d2);
            else {
                printf("Plesae enter your d2 again!\n");
                goto gtd1;
            }
            break;
        default:
            printf("please input effective keyword\n"); 
            break;
    }
}

}