C语言菜单程序

/* menuette.c -- menu techniques */
#include <stdio.h>
char get_choice(void);
char get_first(void);
int get_int(void);
void count(void);
int main(void)
{
    int choice;
    void count(void);

    while ( (choice = get_choice()) != 'q')
    {
        switch (choice)
        {
            case 'a' :  printf("Buy low, sell high.\n");
                break;
            case 'b' :  putchar('\a');  /* ANSI */
                break;
            case 'c' :  count();
                break;
            default  :  printf("Program error!\n");
                break;
        }
    }
    printf("Bye.\n");

    return 0;
}

void count(void)
{
    int n,i;

    printf("Count how far? Enter an integer:\n");
    n = get_int();
    for (i = 1; i <= n; i++)
        printf("%d\n", i);
    while ( getchar() != '\n')
        continue;
}

char get_choice(void)
{
    int ch;

    printf("Enter the letter of your choice:\n");
    printf("a. advice           b. bell\n");
    printf("c. count            q. quit\n");
    ch = get_first();
    while (  (ch < 'a' || ch > 'c') && ch != 'q')
    {
        printf("Please respond with a, b, c, or q.\n");
        ch = get_first();
    }

    return ch;
}

char get_first(void)
{
    int ch;

    ch = getchar();
    while (getchar() != '\n')
        continue;

    return ch;
}

int get_int(void)
{
    int input;
    char ch;

    while (scanf("%d", &input) != 1)
    {
        while ((ch = getchar()) != '\n')
            putchar(ch);  // dispose of bad input
        printf(" is not an integer.\nPlease enter an ");
        printf("integer value, such as 25, -178, or 3: ");
    }

    return input;
}