示例

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h> //C99特性
#include <string.h>

char* s_gets(char* st, int n);

enum spectrum {red, orange, yellow, green, blue, violet};
const char* colors[] = {"red", "orange", "yellow", "green", "blue","violet"};
#define LEN 30

/* C允许同名，C++不允许. 例如下面代码：*/
struct rect { double x; double y; };
int rect;

int main(int argc, char* argv[])
{
	char choice[LEN];
	enum spectrum color;
	bool color_is_found = false;

	puts("Enter a color (empty line to quit)：");
	while (s_gets(choice, LEN) != NULL && choice[0] != '\0')
	{
		for (color = red; color <= violet; color++)
		{
			if (strcmp(choice, colors[color]) == 0)
			{
				color_is_found = true;
				break;
			}
		}

		if (color_is_found)
		{
			switch (color)
			{
			case red:
				puts("Roses are red.");
				break;
			case orange:
				puts("Poppies are orange.");
				break;
			case yellow:
				puts("Sunflowers are yellow.");
				break;
			case green:
				puts("Grass are green.");
				break;
			case blue:
				puts("Bluebells are blue.");
				break;
			case violet:
				puts("Violets are violet.");
				break;
			default:
				break;
			}
		}
		else
		{
			printf("I don't know about the color %s.\n", choice);
		}
		color_is_found = false;
		puts("Next color, please (empty line to quit):");
	}
	puts("Goodbye!");

	system("pause");
	return 0;
}


// 自己实现读取函数
char* s_gets(char* st, int n)
{
	char* ret_val;
	int i = 0;
	ret_val = fgets(st, n, stdin);
	if (ret_val) //即，ret_val != NULL
	{
		while (st[i] != '\n' && st[i] != '\0')
			i++;
		if (st[i] == '\n')
			st[i] = '\0';
		else
			while (getchar() != '\n')
				continue;
	}
	return ret_val;
}

运行测试