1、

#include <stdio.h>

enum animal {Dog, Cat, Monkey, Invalid};

void dog(void)
{
    puts("wang wang\n");    
} 

void cat(void)
{
    puts("miao miao\n");
}

void monkey(void)
{
    puts("ji ji\n");
}

enum animal select(void)
{
    enum animal tmp;
    do
    {
        puts("0: dog  1: cat  2: monkey  3: over!");
        printf("tmp = "); scanf("%d", &tmp);
    }
    while(tmp < Dog || tmp > Invalid);
    return tmp;
}

int main(void)
{
    enum animal selected;
    do
    {
        switch(selected = select())
        {
            case Dog : dog(); break;
            case Cat : cat(); break;
            case Monkey : monkey(); break;
        }
    }
    while(selected != Invalid);
    return 0;
}