基于菜单的程序withwhile和switch语句？

Question

我是初学者，我正在努力学习。我自己写了一个switch case语句，这是基于菜单的一个。所有程序都没问题，但是当菜单重新出现时，菜单显示不正确！

代码是

int main()
{
    char menu
    int i,num,fact=1,d;
    while(1)
    {
        printf("enter 'a' to find out factorial of a number\n");
        printf("enter 'b' to find out that number is prime or not\n");
        printf("enter 'c' to find out that number is odd or even\n");
        printf("enter 'd' to exit");
        scanf("%c",&menu);

        switch(menu)
        {
        case 'a':
            printf("please enter the number ");
            scanf("%d",&num);
            for(i=1; i<=num; i++)
                fact=fact*i;
            printf("factorial is %d\n",fact);
            break;

        case'b':
            printf("enter the number");
            scanf("%d",&num);
            for(i=2; i<=num-1; i++)
            {
                if(num%i==0)
                {
                    printf("not a prime number\n");
                    break;
                }
            }
            if(i==num)
            {
                printf("prime number\n");
                break;
            }
            break;

        case'c':
            printf("enter the number\n");
            scanf("%d",&num);
            d=num%2;
            if(d=0)
                printf("its a even number\n");
            else
                printf("its a odd one\n");
            break;

        case'd':
            exit(0);

        }
    }
}

Answer 1

试试这个：

   int ok=1;
    while(1)
    {
        if(ok==1)
        {
        printf("enter 'a' to find out factorial of a number\n");
        printf("enter 'b' to find out that number is prime or not\n");
        printf("enter 'c' to find out that number is odd or even\n");
        printf("enter 'd' to exit\n");
        scanf("%c",&menu);
        fflush(stdin);
        }
        ok=1;

        switch(menu)
        {
        case 'a':
            printf("please enter the number ");
            scanf("%d",&num);
            for(i=1; i<=num; i++)
                fact=fact*i;
            printf("factorial is %d\n",fact);
            break;
        ......
        ......
        default: ok=0;break;

        }
    }

通过此修改，菜单在我的系统上正常工作。

还要查看shekhar suman的答案，以消除明显的错误。