示例：菜单小程序

//Visual Studio中加上这句才可以使用scanf()
//否则只能使用scanf_s()
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdbool.h>

char get_choice(void);
char get_first(void);
int get_int(void);
void count(void);

//argc: 参数个数 argv[]: 参数数组
int main(int argc, char *argv[])
{
	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');//发出蜂鸣声
			break;
		case 'c':
			count();
			break;
		default:
			printf("Program error!\n");
			break;
		}
	}
	printf("Bye.\n");

	system("pause");
	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);
	// 处理输入的多余字符,包括回车
	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); //处理错误输入
		printf(" is not an integer.\nPlease enter an ");
		printf("integer value, such as 25, -178, or 3: ");
	}
	return input;
}

运行测试